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      NOAA Technical Report NIVIFS 85                                             March 1990

                       Marine Farming and Enhancement

                       Proceedings of the Fifteenth
                       U.S.-Japan Meeting on Aquaculture
                       Kyoto, Japan
                       October 22-23, 1986


                       Albert K. Sparks (editor)




























                       U.S. Department of Commerce

  ;H11
  .A44672
  AO.85








                        NOAA TECHMCAL REPORT NWS


                             The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and geographic distribution of fishery resources, to
                        understand and predict fluctuations in the quantity and distribution of these resources, and to establish levels for their optimum use. NMFS is also charged with the development
                        and implementation of policies for managing national fishing grounds, development and enforcement of domestic fisheries regulations, surveillance of foreign fishing off United
                        States coastal waters, and the development and enforcement of international fishery agreements and policies./NMFS also assists the fishing industry through marketing service
                        and economic analysis programs, and mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishes statistics on various phases ofthe industry.
                             The NOAA Technical Report NMFS series was established in 1983 to replace two subcategories of the Technical Reports series: "Special Scientific Report-Fisheries" and
                        "Circular." The series contains the following types of reports: Scientific investigations that document long-term continuing programs of NMFS; intensive scientific reports on
                        studies of restricted scope; papers on applied fishery problems; technical reports of general interest intended. to aid conservation and management; reports that review in con-
                        siderable detail and at a high technical level certain broad areas of research; and technical papers originating in economics studies and from management investigations. Since
                        this is a formal series, all submitted papers receive peer review and those accepted receive professional editing before publication.
                             Copies of NOAA Technical Reports NMFS are available free in limited numbers to governmental agencies, both Federal and State. They are also available in exchange for
                        other scientific and technical publications in the marine sciences. Individual copies may be obtained from: U.S. Department of Commerce, National Technical Information Service,
                        5285 Port Royal Road, Springfield, VA 22161. Although the contents have not been copyrighted and may be reprinted entirely, reference to source is appreciated.


                        48. Widow rockfish: Proceedings of a workshop, Tiburon, California, December                  64. Illustrated key to penaeoid shrimps of commerce in the Americas, by Isabel P6rez
                        11-12, 1980, by William H. Lenarz and Donald R. Gunderson (editors). January 1987,            Farfante. April 1988, 32 p.
                        57 p.
                                                                                                                      65. History ofwhaling in and near North Carolina, by Randall R. Reeves and Edward
                        49. Reproduction, movements, and population dynamics of the southern kingfish,                Milchell. March 1988, 28 p.
                        Menticirrhus americanus, in the northwestern Gulf of Mexico, by Stephen M. Harding
                        and Mark E. Chittenden, Jr. March 1987, 21 p.                                                 66. Atlas and zoogeography of common fishes in the Bering Sea and northeastern
                                                                                                                      Pacific, by M. James Allen and Gary B. Smith. April 1988, 151 p.
                        50. Preparation of acetate peels of valves from the ocean quahog, Arctica islandica,
                        for age determinations, by John W. Ropes. March 1987, 5 p.                                    67. Index numbers and productivity measurement in multispecies fisheries: An
                                                                                                                      application to the Pacific coast trawl fleet, by Dale Squires. July 1988, 34 p.
                        51. Status, biology, and ecology of fur seals: Proceedings        of an international
                        workshop, Cambridge, England, 23-27 April 1984, by John P.        Croxall and Roger           68. Annotated bibliography H of the hard clam Mercenaria mercenaria, by J.L.
                        L. Gentry (editors). June 1987, 212 p.                                                        McHugh and Marjorie W. Sumner. September 1988, 59 p.

                        52. Limited access alternatives for the Pacific groundfish fishery, by Daniel D.              69. Environmental quality and aquaculture systems: Proceedings of the thirteenth
                        Huppert (editor). May 1987, 45 p.                                                             U.S.-Japan meeting on aquaculture, Mie, Japan, October 24-25, 1984, edited by Carl
                                                                                                                      J. Sindermarm. October 1988, 50 p.
                        53. Ecology of east Florida sea turtles: Proceedings of the Cape Canaveral, Florida,
                        sea turtle workshop, Miami, Florida, February 26-27, 1985, by Wayne N. Witzell                70. New and innovative advances in biology/engineering with potential for use in
                        (convener and editor). May 1987, 80 p.                                                        aquaculture: Proceedings of the fourteenth U.S. -Japan meeting on aquaculture, Woods
                                                                                                                      Hole, Massachusetts, October 16-17, 1985, edited by Albert K. Sparks. November
                        54. Proximate and fatty acid composition of 40 southeastern U.S. finfish species,             1988, 69 p.
                        by Janet A. Gooch, Malcolm B. Hale, Thomas Brown, Jr., James C. Bonnet, Cheryl
                        G. Brand, and Lloyd W. Reiger. June 1987, 23 p.                                               71. Greenland turbot Reinhart1rius hippoglossoides of the eastern Bering Sea and
                                                                                                                      Aleutian Islands region, by Miles S. Alton, Richard G. Bakkala, Gary E. Walters,
                        55. Proximate composition, energy, fatty acid, sodium, and cholesterol content of             and Peter T. Munro. December 1988, 31 p.
                        finfish, shellfish, and their products, by Judith Krzynowek and Jenny Murphy. July
                        1987, 53 p.                                                                                   72. Age determination methods for northwest Atlantic species, edited by Judy Perittila
                                                                                                                      and. Louise M. Dery. December 1988, 135 p.
                        56. Some aspects of the ecology of the leatherback turtle Dermochelys cori"ea at
                        Laguna Jolova, Costa Rica, by Harold F. Hirth and Larry H. Ogren. July 1987, 14 p.            73. Marine flora and fauna of the Eastern United States. Mollusca: Cephalopoda,
                                                                                                                      by Michael Vecchione, Clyde F.E. Roper, and Michael J. Sweeney. February 1989,
                        57. Food habits and dietary variability of pelagic nekton off Oregon and Washington,          23 p.
                        1979-1984, by Richard D. Brodeur, Harriet V. Lorz, and William G. Pearcy. July
                        1987, 32 p.                                                                                   74. Proximate composition and fatty acid and cholesterol content of 22 species of
                                                                                                                      northwest Atlantic finfish, by Judith Krzynowek, Jenny Murphy, Richard S. Maney,
                        58. Stock assessment of the Gulf menhaden, Brevoordapatronus, fishery, by Douglas             and Laurie J. Panunzio. May 1989, 35 p.
                        S. Vaughan. September 1987, 18 p.                                                             75. Codend selection of winter flounder Pseudopleuronecres americanus, by David
                        59. Atlantic menhaden, Brevoortia tyrannus, purse seine fishery, 1972-84, with a              G. Simpson. March 1989, 10 p.
                        brief discussion of age and size composition of the landings, by Joseph W. Smith,             76. Analysis of fish diversion efficiency and survivorship in the fish return system
                        William R. Nicholson, Douglas S. Vaughan, Donnie L. Dudley, and Ethel A. Hall.                at San Onofre Nuclear Generating Station, by Milton S. Love, Meenu Sandhu,
                        September 1987, 23 p.                                                                         Jeffrey Stein, Kevin T. Herbinson, Robert H. Moore, Michael Mullin, and John S.
                        60. Gulf meRhaden, Brevoortia patronus, purse seine fishery, 1974-85, with a brief            Stephens, Jr. April 1989, 16 p.
                        discussion of age and size composition of the landings, by Joseph W. Smith, Eldon             77. Illustrated key to the genera of free-living marine nematodes of the order
                        J. Levi, Douglas S. Vaughan, and Ethen A. Hall. December 1987, 8 p.                           Enoplida, by Edwin J. Keppner and Armen C. Tarjan. July 1989, 26 p.
                        61. Manual for starch gel electrophoresis: A method forthe detection of genetic varia-        78. Survey of fishes and water properties of south San Francisco Bay, California,
                        tion, by Paul B. Aebersold, Gary A. Winans, David J. Teel, George B. Milner, and              1973-82, by Donald E. Pearson. August 1989, 21 p.
                        Fred M. Utter. December 1987, 19 p.
                                                                                                                      79. Species composition, distribution, and relative abundance of fishes in the coastal
                        62. Fishery publication index, 1980-85; Technical memoradum index,       1972-85, by          habitat off the southeastern United States, by Charles A. Wenner and George R.
                        Cynthia S. Martin, Shelley E. Arenas, Jacki A. Guffey, and Joni M. Packard.                   Sedberry. July 1989, 49 p.
                        Oecember 1987, 149 p.
                                                                                                                      80. Laboratory guide to early life history stages of northeast Pacific fishes, by Ann
                        63. Stock assessment of the Atlantic menhaden, Brevoortia tyrannus, fishery, by               C. Matarese, Arthur W. Kendall, Jr., Deborah M. Blood, and Beverly M. Vinter.
                        Douglas S. Vaughan and Joseph W. Smith. January 1988, 18 p.                                   0&.ober.1989, 651,.p.












                                                                         NOAA Technical Report NMFS 85


                                                                         Marine Farming and Enhancement

                                                                         Proceedings of the Fifteenth
                                                                         U.S. Japan Meeting on Aquaculture,
                                                                         Kyoto, Japan
                                                                         October 22-23, 1986


                                                                         Albert K. Sparks (editor)


                                                                         Panel Chairmen:
                                                                         Conrad Mahnken, United States
                                                                         Ikuo Ikeda,Japan


                                                                         Under the U.S. Japan Cooperative Program
                                                                         in Natural Resources (UJNR)


                                                                         March 1990










                                                                         U.S. DEPARTMENT OF COMMERCE
                                                                         Robert Mosbacher, Secretary
                                                                         National Oceanic and Atmospheric Administration
                                                                         John A. Knauss, Under Secretary for Oceans and Atmosphere
                                                                         National Marine Fisheries Service
                                                                         William W. Fox, Jr., Assistant Administrator for Fisheries






                
                                                                       LIBRARY
                                                                     NOAA/CCEH
                                                                  1990 HOBSON AVE
              CC)
                                                               CHAS. SC 29408262
 










                                                  PREFACE


                                                  The United States and Japanese counterpart panels on aquaculture were formed in 1969
                                                  under the United States-Japan Cooperative Program in Natural Resources (UJNR). The
                                                  panels currently include specialists drawn from the federal departments most concerned
                                                  with aquaculture. Charged with exploring and developing bilateral cooperation, the panels
                                                  have focused their efforts on exchanging information related to aquaculture which could
                                                  be of benefit to both countries.
                                                        The UJNR was begun during the Third Cabinet4,evel Meeting of the Joint United States-
                                                  Japan Committee on Trade and Economic Affairs in January 1964. In addition to aqua-
                                                  culture, current subjects in the program include desalination of seawater, toxic micro-
                                                  organisms, air pollution, energy, forage crops, national park management, mycoplasmosis,
                                                  wind and seismic effects, protein resources, forestry, and several joint panels and commit-
                                                  tees in marine resources research, development, and utilization.
                                                        Accomplishments include: Increased communication and cooperation among technical
                                                  specialists; exchanges of information, data, and research findings; annual meetings of the
                                                  panels, a policy-coordinative body; administrative staff meetings; exchanges of equipment,
                                                  materials, and samples; several major technical conferences; and beneficial effects on
                                                  international relations.



                                                                                                                              Conrad Mahnken - United States
                                                                                                                                                  Ikuo Ikeda - Japan

































                                                                         The National Marine Fisheries Service (NMFS) does not approve, recom-
                                                                         mend or endorse any proprietary product or proprietary material mentioned
                                                                         in this publication. No reference shall be made to NMFS, or to this publica-
                                                                         tion furnished by NMFS, in any advertising or Wes promotion which would
                                                                         indicate or imply that NMFS approves, recommends or endorses any pro-
                                                                         prietary product or proprietary material mentioned herein, or which has as
                                                                         its purpose an intent to cause directly or indirectly the advertised product to
                                                                         be used or purchased because of this NMFS publication.






         CONTENTS


         Prentice, Earl F.
             A new internal telemetry tag for fish and crustaceans 1
         Matlock, Gary C.
             Preliminary results of red drum stocking in Texas 11
         Utter, Fred M., and James E. Seeb
             Genetic marking and ocean farming 17
         Smith, Theodore I.J.
             Culture of North America sturgeons for fishery enhancement 19
         Polovina, Jeffrey J.
             Application of yield-per-recruit and surplus production models to fishery enhancement
             through juvenile releases 29
         Ito, Ifiroshi
             Some aspects of offshore spat collection of Japanese scallop 35
         Westley, Ronald E., Neil A. Rickard, C. Lynn Goodwin, and Albert J. Scholz
             Enhancement of molluscan shtilfish in Washington State 49
         Manzi, John J.
             The role of aquaculture in the restoration and enhancement of molluscan fisheries in
             North America 53

         Lee, Cheng-Sheng, and Clyde S. Tamaru
             Application of LHRH-a cholesterol pellets to maturation of finfish: milkfish 57
         Chew, Kenneth K.
             Trends in oyster cultivation on the west coast of North America 65
         Hirayama, Kazutsugu
             A physiological approach to problems of mass culture of the rotifer 73
         Fujita, Naoji, and Katsuyoshi Mori
             Effects of environmental instability on the growth of the Japanese scallop Patinopecten yessoensis in
             Abashiri sowing-culture grounds 81
         Yamazaki, Makoto
             Mantis shrimp: Its fishery and biological production 91
         Inoue, Kiyokazu
             Growth and survival of artificial abalone seed released in Shijiki Bay, Japan 101
         Kimoto, Katsunori
             Copepod swarms observed by SCUBA diving in a small inlet of Kyushu, Japan 105
         Sudo,11iroyuki
             Feeding ecology of young red sea bream in Shijiki Bay 111
         Fukuhara, Osamu
             Importance of qualitative evaluation of hatchery-bred fish for aquaculture 117
         Suda, Akira
             Recent progress in artificial propagation of marine species for Japanese sea-farming and
             aquaculture 123






              A New Internal                                                             The recognition of an animal or a group of animals within
                                                                                         a population is important for many reasons in fisheries re-
              Telemetry Tag for                                                          search. Many types of tags and marks have been developed
                                                                                         to aid biologists in recognizing animals (Rounsefell 1963,
              F&h md Crustacems                                                          Farmer 1981). Unfortunately, no one technique has been
                                                                                         totally satisfactory from a biological or technical standpoint.
                                                                                         In 1983, the National Marine Fisheries Service began a study
                                                                                         supported by the Bonneville Power Administration to evalu-
              EARL E PRENTICE                                                            ate the technical and biological feasibility of adapting a new
              Coastal Zone and Estuarine Studies                                         identification system to salmonids. The system is based upon
              Northwest Fisheries Center                                                 a passive integrated transponder (PIT) tag. This tag has the
              National Marine Fisheries Service, NOAA                                    promise of eliminating some of the inherent problems with
              Manchester Field Station                                                   present tagging and marking systems. In addition to the re-
              P.O. Box 130                                                               search with salmonids, preliminary tagging studies have also
              Manchester, Washington 98353                                               been conducted with two crustacean species. This paper
                                                                                         provides an overview of the basic tag operation, biological
                                                                                         acceptability in test animals, field testing results, and a dis-
              ABSTRACT                                                                   cussion of some of the possible applications of the PIT tag.

              An ongoing cooperative agreement between the Bonneville                    Tag operation
              Power Administration and the National Marine Fisheries Service
              was initiated in 1983 to evaluate the technical and biological
              feasibility of adapting a new identification system to salmonids.          The PIT tag consists of an antenna coil that has about 1,500
              The system is based on a passive integrated transponder (PIT)              wraps of a special coated, 0.0254-mm diameter copper wire.
              tag. Each tag measures 12 nun in length by 2.1 nun in diam-                The antenna coil is bonded to a integrated circuit chip. The
              eter and is uniquely coded with one of 34 billion codes. The tag's         electronic components of the tag are encapsulated in a glass
              operational life is unknown at this time; however, it is thought           tube about 12 min long and 2.1 mm in diameter (Fig. 1).
              to be 10 or more years. The tag can be detected and decoded                Each tag is preprogrammed at the factory with one of about
              in place, eliminating the need to anesthetize, handle, or restrain         34 billion unique code combinations. The tag is passive,
              fish during data retrieval.                                                having no power of its own, and thus must rely upon an
                Biological tests indicate the body cavity of juvenile and adult          external source of energy to operate. A 400-KHz signal
              satmonids is biologically acceptable for tag implantation. Com-            energizes the tag, and a unique 40-50 KHz signal is trans-
              parisons between PIT-tagged and traditionally tagged and                   mitted back to the interrogation equipment where the code
              marked juvenile salmonids are discussed. Laboratory and field
              tests showed that the PIT tag did not adversely affect growth              is immediately processed and displayed, transmitted to a com-
              or survival, nor was there any appreciable tissue response to              puter via an RS-232 interface, and/or placed on printed hard
              the tag. No evidence of infection due to tagging procedures was            copy. A portable hand reader (Fig. 2) or a fixed tag-monitor
              observed. Video-taped swim-chamber tests showed no signifi-                system is used to interrogate and display the tag code infor-
              cant effect of the PIT tag on respiratory rate, tail beat frequency,       mation. Data transfer rate is 4,000 bits/s. The interrogation
              stamina, or post-fatigue survival of juvenile salmonids. Tag               range of the tag varies with the monitoring equipment used:
              retention within the body cavity was near 100% for salmonids               Using a hand reader the reading range is up to 7.6 cm, while
              weighing from 2 to 10,000 g. Previously PIT-tagged mature                  with a fixed full-loop interrogator the reading range of detec-
              salmon which were hand stripped of sperm and eggs showed                   tion is about 18 cm, (Fig. 3). The tag can be read through
              high tag retention with no adverse tag-caused effects.
               During their outmigration, PIT-tagged juvenile salmonids
              were successfully interrogated at two dams using automatic tag-
              monitoring equipment. All data were automatically recorded                                                                   0
              and stored by computer. PIT-tag reading efficiency was % to                       Glass tube     Antenna               =hip
              100%, while reading accuracy was over 99%. The tag-monitor-
              ing equipment proved to be reliable under field conditions.                                                                           T
               Special tagging considerations with Crustacea and preliminary                                                                        2.1 mm
              testing of the PIT tag with two crustacean species are discussed,
              along with future applications of the PIT tag to fisheries                   IL               -12mm
              research.

                                                                                         I

                                                                                                                     Figure 1
                                                                                                                      PIT tag.











                                                                                                                                                                 270 -



                                                                                                                                                                 250-


                                                                                                                                                                 230-                                       PIT tagged group,
                                                                                                                                                                 210 -                                                                  Control group


                                                                                                          @01       _,V
                                                                                                                                                                 190
                                                                                                                                                          E
                                                                                                                                                          E
                                                                                                                         77,
                                                                                                                                                                 170-
                                                                                 _J@

                                                                                                                                                                 150 -
                                                                          Figure 2                                                                        0
                                                                                                                                                          LL
                                                  Portable hand-operated PIT-tag reader.
                                                                                                                                                                 130



                                                                                                                                                                 110



                                                                                                                                                                 90 -
                                           Dual loop antenna assembly                       Dual loop antenna assembly
                                                                                                     XShield box@'=-M=
                                                       Shield box r
                                                                                                                                                                 70
                                                                                 (-FLOW
                                                   Coil A       Coil B                               C    A         Coil B                                            0        T50          100         150         200         250         300        350
                                                                                                     ,     =,@                                                            Seawater
                                               Loop tuner Loop tuner                            Loop tuner Loop tuner                                                        entry                           Days
                                                       Dual exciter                                       Dual  excite                                                                             Figure 4
                                                       assembly                                           aernb,'                                    Comparison of length change between PIT-tagged (broken Hne) and con-
                                                                                                          1$1                                               i:rol (solid line) fall chinook salmon (1984 brood) over time.
                                                       Dualpower                                          Dual power
                                                       supply                                             supply


                                                                                                                                                          No special permits are required of the operator other than
                                    To other                                                                                To other                 those obtained from the Federal Communications Comirnis-
                               downslTam               Controller                Multiport                Controller        upstream
                                    monitors                                                                                monitors                 sion (FCC) or their equivalent for the operation of low-
                                                                                                                                                     powered transmitting devices. These permits pertain only to
                                                         Printer
                                                                                                                                                     specialized monitoring systems and not the hand-held system
                                                                                                                                                     already certified by the FCC. No special training or licens-
                                                                                 Computer
                                                                                                                                                     ing of the operator is required to operate the tag-monitoring
                                                                                                                                                     equipment.
                                                   ------------------                           -------------------                                       PIT tag operational life is currently being investigated.
                                                                                                                                                     Two 300-fish test groups ofjuvenile fall chinook salmon were
                                                                                                                                                     established: One control group (no tag), and one tag group.
                                                                                                                                                     All fish in each test group were weighed and measured at
                                                                          Figure 3                                                                   the time the test groups were established. The two test groups
                                             Typical PIT-tag monitoring system for dams.                                                             were maintained in freshwater until smolted and then trans-
                                                                                                                                                     ferredtoispawater where they are being held in separate sea
                                                                                                                                                     cages.-Obser'vations on growth, survival, and tag retention
                                                                                                                                                     and operation -were made at various intervals. Results after
                           soft and hard tissue, liquid (seawater and freshwater), glass,                                                            250 days show no meaningful difference in growth (Fig. 4)
                           and plastic, but not through metal, Extreme heat or cold (60                                                              or survival between groups of tagged and control fish. Tag
                                                                                                  r-M -             "   ,
                                                                                                  I Istearn monitoy
                                                                                                     oil













                                                                         ----------- 11















                           to -90'C) does not appreciably affect detection or reading                                                                retention and operation have been 100%. Because of the
                           of the tag. Successful tag monitoring can take place at                                                                   passive nature of the tag, an operational life of 10 years or
                           velocities up to 30 cm/s.                                                                                                 moire is expected.



                                                                                                                                              2






               Biological suitability: Salmonids                                                                                  Table 1
                                                                                                       Summary of wound condition after tagging and tag location within
               It is important that a tagging system does not alter growth,                            the body cavity of juvenile fall chinook salmon over time with descrip-
               survival, behavior, or reproduction. In addition, tag longevity                               tions of wound condition and tag location codes.
               (tag retention and operational life) is an important considera-                                                               Days post-tagging
               tion. Laboratory tests were conducted to examine these fac-
               tors as they apply to the use of the PIT tag with salmonids.                                  Code                    40-45             97             127
               Juvenile and adult chinook (Oncorhynchus tshawytscha),                                                                                                     -
               Atlantic salmon (Salmo salar), and steelhead (Salmo gaird-                              Wound code'                Percent fish within a classification code
               nen) were used in the studies. The fish ranged in weight from                           A                              7.3              0              0.6
               2 to 10,000 g. All tags were injected into the body cavity                              B                              8.3              0              0.2
               using a modified hypodermic syringe and a 12-gauge needle                               C                             84.4              100.0          99.2
               (Prentice et,al. 1986).                                                                 Tag location code'
                                                                                                       A                              2.1              0              3.9
                                                                                                       B                             86.5              69.1           83.3
               Tissue response                                                                         C                              0.0              4.4            1.0
               Adverse tissue response to the tagging needle and tag has                               D                              5.2              25.0           6.9
                                                                                                       E                              6.3              1.5            4.9
               been minimal. Tag-wound condition and tag placement within
               the body cavity were documented by sacrificing groups of                                'A Open wound.
               juvenile fall chinook salmon over time (Table 1). In nearly                             BWound that is closed by a thin membrane and is healing; at times
               85 % of the fish examined (n = 195) the tag wound was com-                               a slight red or pinkish coloration is noticeable in the area of the
                                                                                                        wound.
               pletely healed by day 40-45, with only a scar indicating the                            CWound completely healed that may or may not be noticeable by
               area of needle insertion. At the end of this same period, 7.3 %                          the presence of a scar. No red or pink coloration in the area of
               of the fish had an open wound and 8.3 % had a wound that                                 the wound.
               was closed but slightly discolored. All fish (n = 99) sacra-                            'A Tag located between pyloric caeca and mid-gut.
               ficed 97 days post-tagging showed complete healing of epi-                              BTag located near abdominal musculature and often embedded in
                                                                                                        the posterior area of pyloric caeca near the spleen or in adipose
               dermal and subcutaneous tissue. A the termination of the                                 tissue at the posterior area of pyloric caeca.
               study (day 127) an additional 102 fish were sacrificed; 99.2 %                          CTag found in an area other than those noted; generally between
               had completely healed tagging wounds, 0.6% had open                                      mid-gut and air bladder or between liver and pyloric caeca.
               wounds, and 0.2% had wounds that were closed but dis-                                   DNo tag present.
               colored. The study also indicated that once the tag was in-                             ETag partially protruding through abdominal wall.
               jected into the body cavity, its location was stable over time.
               The majority of tags were found near the posterior end of
               the pyloric caeca.                                                                 from each fish. Tag retention was 100% for the males. A
                                                                                                  total of 48 females were spawned. Tag retention was 83 %
               Effects of maturing fish                                                           for spawning fernales and 100% for non-spawners. Four tags
                                                                                                  were passed during the first stripping and four tags during
               Numerous morphological and physiological changes take                              the second-fourth stripping (Table 2). When a tag was passed,
               place as salmon mature. These changes may alter the re-                            it was easily recognized among the eggs. The presence of
               sponse of fish to foreign material such as a PIT tag. Further-                     tags caused no observable adverse effects on the eggs.
               more, it is necessary to know whether a tag placed in the
               body cavity would cause internal damage to eggs and whether
               a tag would be retained during spawning. A study addressing                                                         Table 2
               these issues was conducted using 21 male and 60 female                                  Spawning dates and PIT-tag rejection by female Atlantic salmon.
               maturing Atlantic salmon. The fish ranged in weight from
               2,500 to 10,000 g and in length from 61 to 80 cm. All fish                              Date         No. females          Cumulative            No. tags
               were PIT tagged intraperitoneally using the method of Pren-                             spawned        spawned            no. spawned         not retained
               tice et al. (1986). The fish were examined several times prior                          21 Oct             21                  21                      1.
               to spawning to determine wound condition, tag retention,                                22 Oct              4                  25                      0
               readiness to spawn, and general condition, and scanned for tag                          23 Oct              7                  32                      0
               code using a hand-held scanning unit. When fish were deter-                             25 Oct              7                  39                      2b
                                                                                                       29 Oct              3                  42                      Y
               mined to be ready to spawn, eggs were collected by hand strip-                          4 Nov               6                  48                      2d
               ping. Individuals that spawned were subject to 1-4 strippings.
                  During the study, no adverse tissue reaction was noted.                              'One tag not retained during I st stripping.
               AD tagging wounds were closed and healing by the third (lay                             bOne tag not retained during 3d and 4th stripping.
                                                                                                       'One tag not retained during I st, 2d, and 4th stripping.
               after tagging. No infection or discoloration was noted in the                           dTwo tags not retained during I st stripping.
               area of the tag. All 21 males matured, and milt was collected

                                                                                              3








                                                                                          Table 3
                                    Comparison of survival, growth, and PIT-tag retention for the 1986 fall chinook salmon serial-tagging study.

                                                                                                    Size (g)
                               Treatment* and                              Test length                                     Survival         PIT-tag retention
                                  test group            No. days               (9)              start        end             (%)                   (%)

                               Control-well                202                 135              4.9          24.9            100.0
                               Control-stream              200                 135              5.1          24.8            99.0                      -
                               PIT tagged
                                 well #1                   201                 139              3.2          20.5            99.5                  100.0
                                 well #2                   200                 135              5.1          27.4            100.0                 100.0
                                 well #3                   201                 134              7.1          25.9            100.0                 100.0
                                 well #4                   200                 137              9.7          32.6            97.0                  100.0

                                 stream #1                 200                 139              3.2          21.1            95.0                  99.0
                                 stream #2                 200                 135              4.8          22.6            98.0                  100.0
                                 stream #3                 203                 134              7.3          29.9            95.0                  100.0
                                 stream #4                 202                 137              10.0         30.3            98.0                  100.0

                               *Well-constant temperature (10*C) pathogen-free artesian well-water rearing; stream-ambient temperature (9.3-14.4*C) Big
                               Beef Creek surface-water rearing.



                  Growth and survival                                                             primarily in the stream-water,.eld groups (Table 3). Visual
                                                                                                  examination indicated that these populations of fish -were"
                  Tests were conducted in         1986 using juvenile fall chinook
                  salmon to determine the minimum size that could be suc-                         Various stages of smoltification. Reductions in immune m-
                  cessfully PIT tagged. Fish were tagged at four size ranges                      sponse have been noted during smoltification (Maule and
                  and held in separate holding containers (Table 3). The num-                     Schreck 1987). It is possible that exposure to pathogens in
                  ber of fish in each test group ranged from 200 to 203. Fish                     the stream water, and/or smoltification status itself, contrib-
                  ranged in weight and length from 1.7 to 14.9 g and 56 and                       uted. to these mortalities. The data suggest that fish weigh-
                  120 mm, respectively, at the time of tagging. Two separate                      ing @3 g (mean weight) or less, or those undergoing smolti-
                  water supplies (well water and stream water) were used in                       ficallon, experience a low mortality (5 % or less) when PIT
                  the study to determine if exposure to water containing fish                     tagged.
                  pathogens might affect tag-wound healing or tag retention.
                  Four sets of weight and length data were obtained on each                       Effects on swimming ability
                  group of fish during a 134-139 day period. Tag retention                        Tests were conducted to evaluate the physiological/behavioral
                  was excellent for both groups (99-100%). Growth compari-                        effects of the PIT tag on swimming ability in juvenile steel-
                  sons (both between the PIT-tag        'ged well- and strearn-water              head. The test were conducted in a modified version of a
                  groups, and with the control groups) indicated slight differ-                   Blaska respirometer-stamina chamber described by Smith and
                  ences in length and weight at some sampling periods. How-                       Newcomb (1970) (Fig. 5). Two size ranges of fish were
                  ever, there appears to be no observable pattern to the differ-                  tested. The first group, tested in July 1995, averaged 81 min
                  ences, suggesting that the glass-encapsulated PIT tag does                      in length and 6.5 g in weight. The second test group, in
                  not compromise growth in juvenile salmonids reared in either                    October 1985, averaged 112 min in length and 17.2 g in
                  well- or streamwater. Range of overall (134-139 days) sur-                      weight. In both tests a random sample of fish (n = 200) was
                  vival of PIT-tagged fish was 97-100% in the wen-water                           removed from the main population and intraperitoneally
                  groups and 95-98% in the stream-water groups. Visual in-                        tagged with PIT tags using the procedures of Prentice et al.
                  spection of the data (Table 3) shows that mortality occurred                    (1986). A control (non-tagged) group (n = 200) was also
                  in the smallest size groups of fish for both well- and stream-                  established from the main population at this time. Swimming
                  water groups. Examination of mortalities for both initial well-                 tests were conducted on days 0 (same day as tagging), 1,
                  and stream-water groups showed perforation of the intestine                     2, 3,,4, 7, 9, 11, 14, 17, 21, and 25, with 12 tagged and
                  as the cause of death. Four of the seven mortalities in the                     4 control fish tested each day. All tests were recorded on
                  first stream-water test group occurred within the first 2 days                  video tape and monitored at slow speed to determine swim-
                  after tagging and were from the first 10 fish tagged. Because                   ining stamina (time to impingement), tail-beat frequency per
                  this was the first group of fish to be tagged in the year, our                  minute, respiratory rate (opercular rate/min), and stride
                  tagging technique was not up to standard. Tagging technique                     efficiency (no. tail beats/min required to maintain a unit
                  was refined and no further problems with intestinal perfor-
                  ation was observed in the other test groups. Mortality in the                   swimming speed of one body length/s). All tested fish (tagged
                                                                                                  and control) were held for 14 days post-test to establish stress
                  larger size groups was variable (5 % or less) and occurred                      survival profiles.

                                                                                             4






                                       4      5     6    7  8 9   10                                 1 1                  13


                                  2
                        1                                                   SIDE VIEW
                              F@                                                  I
                                                                                  W1 5


                                                                                                          16            10
                     1  Variable speed control           9.   Electrified screen
                     2. Motor                            10.  Test compartment
                     3. Tachometer                       11.  Removable vane
                     4. Pulley                           12.  Outflow
                     5. End plate                        13.  End plate (removable for fish loading)
                     6. Propeller                        14.  Inflow
                     7. Outer tube (plexiglass)          15.  Axle for tilting chamber
                     8. Inner tube (plexiglas)           16.  Compartment divider                           END VIEW                                       Figure 5
                                                                                                                                 1        Blaska respirometer-stamina chamber.


                  The swimming stamina, stride efficiency, and respiratory                                  chinook salmon, and steelhead. The tests were conducted at
               rate data were compared between tagged and control fish,                                     Lower Granite Dam on the Snake River and McNary Dam
               and between post-tag testing data using the non-parametric                                   on the Columbia River. The survival of PIT-tagged fish was
               Mann-Whitney test. All data analyses followed the methods                                    compared with that of control fish (handled but not tagged),
               of Sokal and Rohlf (1981). The data indicated that neither                                   coded-wire tagged (CWT), CWT plus cold branded, and cold
               the act of tagging nor the presence of the PIT tag com-                                      branded. Fish from all treatments were combined in a com-
               promised swimming stamina, stride efficiency, or respira-                                    mon holding cage, since each treatment could be recognized
               tory rate of juvenile steelhead. In addition, post-test survival                             by its identifying mark or tag. Five replicates of 25 fish per
               was not affected by the PIT tag, and tag retention was 100%.                                 treatment for a total of 125 fish per replicates were used in
               At the termination of the post-test holding period, all PIT-                                 the 1985 test. In the 1986 tests, 20 fish per treatment were
               tagged fish were sacrificed and necropsies performed to                                      used for a total of 100 fish per replicate. The fish were held
               determine tissue reaction to the tags. No adverse tissue reac-                               for 14 days in five cages that received a continuous supply
               tions or tag migrations within the peritoneal cavity were                                    of untreated ambient river water. The fish were examined
               noted.                                                                                       daily for mortality.
                                                                                                              No difference in survival between'fish injected with the
               Comparisons with traditional tagging                                                         PIT tag and in the other treatment groups was noted at the
               and marking methods                                                                          end of 14 days of holding (Table 4). Mortality varied be-
                                                                                                            tween dams but not between test groups at a dam. All PIT-
               A series of tests comparing the PIT tag to traditional methods                               tagged fish showed complete closure of the tagging wound
               of marking and tagging was conducted under field condi-                                      at the end of 14 days. No infection or fungus was observed
               tions using active, outmigrating spring chinook salmon, fall                                 around the tagging would prior to healing.



                                                                                                 Table 4
                              Summary of tests comparing the survival of PIT-tagged fish with that of traditionally tagged and marked fish at dams
                                                                               along the Snake and Columbia rivers.

                                                                                                                                  Survival


                                                                                       Days                                                                        CWT +
                                       Location                   Species            observed        Control         PIT       Cold-branded         CWT         cold-branded

                              Lower Granite (1986)            Spring chinook             14              95           98              96              97              99
                              Lower Granite (1986)            Steelhead                  14             100           99             100              99              97
                                             1610,

















                              McNary (1986)                   Spring chinook             14              86           83              86              80              89
                              McNary (1986)                   Steethead                  14              89           87              93              91              94
                              McNary (1986)                   Fall chinook               14              64           65              59              68              66
                              McNary (1985)                   Fall chinook               14              96           87              94              92              93         1

                                                                                                      5










                                                                  CANAD    A




                                                                                                                                  IDAHO
                                                                                        Wells                                  I
                                                                       Rocky Reach
                                                                        Rock Island              CO/- bi. R.                   I
                                                                                                                               I
                                                                           Wanapurn              Lowe,                         I
                                        WASHINGTON                       Priest Rapids           Monumentall Snake R. Lower
                                                                                                     411@                    Granite
                                                                                                                 Little
                                                                                                                 Goose            lvvwshak@
                                                                                                       lee Harbor                 Hatchery
                                                                                       River                                            on
                                              Bonneville C011mbia      River                        McNary                                                                      Figure 6
                                                                           John Day                       OREGON                                  Location of hydroelectric dams on the Snake and Colum-
                                                          The Dallas                                            0      20  40k@
                                                                                            Approxin@ate Scale p:=:pNEq                                                         bia rivers.








                                                                                                             C-Slot
                                                                                                             gatewell
                                                                                                                       A-slot
                                                                                                                       gatewell


                                                                                                                             Bypass
                                                                                                                             channel


                                                Transport
                                                barge
                                                                       W
                                                                 Race    ays                                           raveling
                                                                                                                  screen
                             Marking                                              Wet separator
                                    and                                         Upwell
                            handling
                               facility                                                              +_ Bypass pipe


                                                  Transport
                                                  truck


                                                                                                                             Forebay
                                                                                                                       Bypass gallery
                                                                                                                       Barrier screen

                                                                                                                          Intake
                                                                                                                        bulkhead
                                                                                                a)                       slot
                                                                                                S91
                                                                                                .S





                                                                                                     T
                                                                                                     Traveling
                                                                                                      r
                                                                                                      screen




                                                                                                                                                                                Figure 7
                                                                                                                                                  Typical hydroelectric dam with juvenile salmon collec-
                                                                                                                                                                              tion facifities.








                                                                                                                         6













                                                                                                                                                       To
                                              Raceways                                                                                             subsample


                               Inclined         Wet      A                                                                                                      PIT tag
                    Upwell                                                                                       To raceway or river                            monitors
                              screen            separator                                                                                                       E and F


                                                                           PIT tag
                                    Sample                               - monitors
                                    tank                                   C and D
                                                                                                                                         PIT tag
                                                                                                                                        monitors           a.
                                    PIT tag                                                                                             C and D
                                                                                                                                                           0
                                    monitors
                                    A and B
                                                                                                                Wet separator
                                                                         PIT tag
                                                                         monitors                      2
                                                                                                                                       'I @'FLO\N
                                                                         E and F                       0
                                                                                                       3:                                FLOW t


                                                                                                                                              ter
                                                                                                                                        sections


                                             ,Raceways
                                                                                                                 orosity control         PIT t9g
                                                                                                                                          monitor
                                                                                                          FP                             A and B   s

                                                                                                                                  Figure 9
                                                                                                    Location of PIT-tag monitors at McNary Dam, Columbia River.

                                               Figure 8
               Location of PIT-tag monitors at Lower Granite Dam, Snake River.
                                                                                                  cess. However, because of the unique features of the PIT
                                                                                                  tag, it could be used in place of the traditional methods,
               Tag detection at dams                                                              generafing better results statistically while using significantly
                                                                                                  fewer fish. With this goal in mind, prototype PIT-tag moni-
               Outmigrating salmonids on the Columbia River system are                            toring systems were installed at two dams. The monitors were
               confronted with a number of hydroelectric dams that cause                          located at the juvenile fish collection facilities at Lower
               decreased migration rates and increased mortality (Fig. 6).                        Granite Dam on the Snake River and McNary Dam on the
               Several of these dams have been modified to collect and/or                         Columbia River. The monitors were placed in positions in-
               divert migrants around them as a method of increasing over-                        suring that 100% of the fish exiting the wet separator were
               all survival in the system. The collection facility generally                      monitored (Figs. 8, 9).
               consists of a series of traveling screens that divert fish from                       A series of tests was conducted to evaluate the operational
               the dam's turbine intakes and eventually into a gallery of                         reliability, tag reading accuracy (correct decoding of the tag),
               pipes that lead to a wet separator (Fig. 7). The separator                         and reading efficiency (percent tagged fish detected) of the
               reduces the volume of water carrying the fish and removes                          dam PIT-tag monitors. Migrating juvenile spring chinook
               debris. Fish are then diverted either to a raceway for later                       salmon, fall chinook salmon, and steethead were used as
               transport downstream via truck or barge, or directly to a                          experimental animals. The tests consisted of releasing 480
               barge for transportation downstream, or back into the river.                       PIT-tagged fish in front of the tag monitors. Tag detection
                                        r6Racelways'
















               A subsample of the fish exiting the wet separator is diverted                      efficiency ranged from 96 to 100%, while tag reading ac-
               into a holding tank and then to an observation room where                          curacy was over 99 %. The monitoring equipment remained
               they are examined for tags and marks.                                              in an active state at the darns for up to 7 months without major
                  Traditionally, methods such as branding and coded-wire                          problems. The PIT-tag monitoring system proved to be reli-
               tagging (CWT) have been used to evaluate oulmigration suc-                         able, efficient, and accurate under field conditions.

                                                                                              7









                                                                                              Table 5
                     Summary of data obtained from the release of PIT-tagged and cold-branded rish into McNary Dam Reservoir, Columbia River, 1985 and 1986.

                                                                        Total fish tagged         Pre-release         Total fish       No. fish         Percent
                     Year           Species             Treatment          and branded            mortality             handled         observed       observed         SD

                     1985       Fall chinook            Branded                4,000                   2.3               13,239             53            19.4*              9
                     1985       Fall chinook            PIT tag                  400                   1.5                  400             64            16.2               4
                     1986       Fall chinook            Branded                5,000                   3.8              201,670             95            27.4*              4
                     1986       Fall chinook            PIT tag                  500                   3.6                  500           142             28.4               1
                     1986       Spring chinook          Branded                5,000                   1.5              154,826           194             38.9*           10
                     1986       Spring chinook          PIT tag                  500                   1.0                  500           318             63.6               2

                     *Expanded value to correct   for subsampling at the dam.





                                                                                              Table 6
                     Summary of data obtained from the release of PIT-tagged and cold-branded fish from Dworshak National Fish Hatchery, Snake River, 1986.


                                                                                                                                Monitor location


                                                                                                          L,ower Granite Dam                         McNary Dam
                                                                                 Pre-release
                                                        Total fish    Total       mortality      No. fish                    Percent      No. fish                      Percent
                         Species        Treatment       handled       released       M           observed    Expanded*       observed     observed     Expanded*       observed

                     Spring chinook     Branded         41,584        40,675         2.2            474         4,659           11.5         362          3,402           8.9
                     Spring chinook     PIT tagged         2,500        2,450        2.0            464           -             18.9         264            -            10.8
                     Steelhead          Branded         35,372         35,025        1.0            571         7,061           20.2          39            389           1.1
                     Steelhead          PIT tagged         2,466        2,424        1.7            928           -             38.1          45            -             1.8

                     *No. fish observed multiplied by   a factor to correct for subsampling at the dam.




                     Additional tests comparing branded and PIT-tagged juve-                         and PIT-tagged fish was similar for each test. Use of the PIT
                  nile migrants (fall chinook salmon, spring chinook salmon,                         tag also aflowed the handling of substantially fewer fish than
                  and steelhead) were made in the field. The fish were released                      did the branding technique to obtain statistically similar
                  into the Snake River of McNary Dam Reservoir and moni-                             results. Fish in the brand treatment were handled at the time
                  tored as they passed through either Lower Granite Dam or                           they were branded and again while being examined at the
                  McNary Dam juvenile collection and monitoring facilities.                          collection facility, along with many nonbranded fish. PIT-
                  In order to obtain sufficiently accurate information on the                        tagged fish, on the other hand, were handled only at the time
                  branded fish, large random subsamples of migrating juve-                           of tagging. It is concluded that the PIT-tagged fish were not
                  niles, some of which were branded, were diverted into col-                         compromised by the tag when released into a river or reser-
                  lection chambers. The subsampled fish were anesthetized and                        voir and that the PIT tag offers substantial gains in efficien-
                  examined visually for brands. On the other hand, PIT-tagged                        cy over branding for many applications.
                  fish were automatically interrogated as they passed by a dam
                  equipped with a PIT-tag monitor system. As each PIT-tagged
                  fish was detected, the tag information, time, date, and loca-                      PIT tagging of crustaceans
                  tion of the fish was automatically entered into a computer
                  and printer. Tables 5 and 6 summarize the results of these                         Permanent identification using external tags and marks for
                  tests. Because branded fish were subsampled, they were                             Crustacea has been difficult because of frequent molting. Ex-
                  detected at a much lower rate than PIT-tagged groups. An                           ternal tags and marks are often lost at the time of molting
                  expansion factor was applied to the brand information to ob-                       or can interfere with the molting process, thus altering the
                  tain an estimation of the true number of branded fish col-                         animal's behavior or physical well-being. Internal coded wire
                  lected (expanded observation value). Since the retrieval of                        (CVIT) tags can eliminate the problem of tag loss at molting
                  PIT-tag information is based on the monitoring of 100% of                          but require the host to be sacrificed to retrieve the tag infor-
                  the fish passing the collection facility at a dam, no expan-                       mation (Prentice and Rensel 1977). The new PIT tag has the
                  sion factor is required and 90-95 % fewer PIT-tagged fish                          potential to eliminate these problems. Preliminary experi-
                  are needed for a study. Pre-release mortality in the branded                       ments using the PIT tag with two species of Crustacea,

                                                                                                8







              Macrobrachium rosenbergii and Cancer tnagister, have been                          Citations
              conducted. The prawns (n = 58) ranged in carapace length
              from 11 to 41 mm and in weight from 1. 5 to 45.3 g. The                            Farmer, A.S.D.
              crabs (n = 52) ranged in width from 64 to 130 min and in                                1981 A review of crustacean marking methods with particular refer-
              weight from 44.4 to 273.2 g. All crabs were tagged in the                                 ence to Penaeid shrimp. Kuwait Bull. Mar. Sci. 2:167-183.
                                                                                                 Manic, A.G., and C.B. Schreck
              thoracic sinus (hemocoel) while the prawns were tagged in                               1987 Changes in the immune system of Coho Salmon (Oncorhynchus
              either the thoracic sinus or abdominal musculature. Results                               kisutch) during the Parr-to-Smolt Transformation and after Implan-
              for both species showed that the tag was retained through                                 tation of Cortisol. Can. J. Fish. Aquat. Sci. 44:161-166.
              molting and the tag information could be obtained rapidly                          Prentice, E.F., and J.E. Rensel
              without sacrificing the tagged animal.                                                  1977 Tag retention of the spot prawn, Pandalusplaiyceros, injected
                                                                                                        with coded wire tags. J. Fish. Res. Board Can. 34:2199-2203.
                                                                                                 Prentice, E.F., D.L. Park, T.A. Flagg, and S. McCutcheon
                                                                                                      1986 A study to determine the biological feasibility of a new fish tag-
              Future applications                                                                       ging system, 1985-1986. Report to Bonneville Power Admin., Con-
                                                                                                        tract DE-A179-83BPI 1982, Proj. 83-19, by Northwest Alaska Fish.
              Based upon biological and technical information gathered to                               Cent., Nad. Mar. Fish. Serv., NOAA, 2725 Montlake Blvd. East,
                                                                                                        Seattle, WA 98112, 879 p. + appendices.
              date and its unique characteristics, the PIT tag will become                       Rounsefell, G.A.
              a valuable tool for a variety of applications in the laboratory                         1963 Marking fish and invertebrates. U.S. Dep. Int., Fish Wildl.
              and field. Its use will not be limited to salmon, prawns, and                             Serv., Bur. Commer. Fish., Fish. Leaflet 549, 12 p.
              crabs but will be applicable to any animal that can accept                         Smith, L.S., and T.W. Newcomb
              and retain the tag without compromise. Examples of advan-                               1970 A modified version of the Blaska respirometer and exercise
                                                                                                        chamber for large fish. J. Fish. Res. Board Can. 27:1331-1336.
              tages and applications of the PIT tag include: (1) Individual                      Sokal, R.R., and F.J. Rohlf
              identification of broodstock; (2) use with groups of animals                            1981 Biometry. W.H. Freeman and Co., San Francisco, xx p.
              where serial measurements, e.g., growth, of individual
              animals are required without sacrificing the animal; (3)
              reduction in the number of replicated treatments in a study
              because each animal is uniquely numbered and can be treated
              as a replicate; and (4) the ability to physically combine dif-
              ferent treatments, since individual animals can be identified,
              removing the variable of rearing-container effect. Other ap-
              plications might include use in behavioral studies where the
              movement of animals can be monitored automatically or
              through capture-recapture methods. It is conceivable that one
              could monitor bottom-dwelling PIT-tagged individuals
              through a grid monitor or a monitor system mounted to an
              underwater sled.
                 The main limitation to the use of the PIT tag, other than
              cost and physical and operational constraints, lies, as with
              most tools, in our imagination. The PIT tag is only the first
              generation of a number of sophisticated identification sys-
              tems growing out of our computer age. We must utilize the
              full potential of these new tools if we are to meet the many
              challenges of fisheries enhancement and aquaculture.

















                                                                                            9










                                                                                     Red drum (Sciaenops ocellatus) is a quasicatadromous
             Rrelhiimary Results of                                                  sciaenid that ranges from Tuxpan, Mexico, in the Gulf of
             Red Drum Stocking                                                       Mexico to Massachusetts in the Atlantic Ocean (Matlock
                                                                                     1984). Adults spawn in oceanic waters nearshore, and lar-
             in Texas                                                                vae are carried by currents through passes into estuarine
                                                                                     nursery areas where they remain for 3 to 5 years before
                                                                                     returning to the ocean to spawn. Economically important
                                                                                     sport and commercial artisinal fisheries have existed since
             GARY C. MATLOCK                                                         the 1800s in Texas, Louisiana, and Florida (Matlock 1980).
             Texas Parks and Wildlife Department                                     However, harvest is being increasingly restricted to insure
             4200 Smith School Road                                                  adequate reproduction and growth to maintain the fishery.
             Austin, Texas 78744                                                     No red drum caught in Florida or the U.S. Fishery Conser-
                                                                                     vation Zone in the Gulf may be retained, and fish caught
                                                                                     in Texas and Alabama may not be sold. Size, bag, and
                                                                                     possession limits exist in all five Gulf states. For example,
             ABSTRACT                                                                only five red drum, all between 457 and 762 mm TL (total
                                                                                     length), can be retained per day in Texas. However, harvest
             The ability to control spawning and to rear red drum (Sciaenops         regulations are not the only options available to managers.
             ocellatus) in captivity has afforded managers the opportunity              Stocking red drum reared in captivity has recently become
             to use stocking to enhance native fisheries. This paper presents        another management tool for this fishery (Rutledge and
             preliminary results of the effects of 2 years of intensive stock-       Matlock 1986). In 1974 red drum were first spawned and
             ing in two Texas estuaries. Catch rates in gill nets fished ran-        reared in captivity (Arnold et al. 1977). The spawning-
             domly in stocked and unstocked bays in spring (April-June) and
             fall (September-November) were compared to determine                    inducement technique, i.e., temperature and photoperiod
             changes in relative abundance of fishable populations. Land-            manipulation, was refined so that fry could be obtained at
             ings by private sport-boat anglers in each bay during the low-          any time (Colura et al. 1976). With fry readily available,
             use (mid-November through mid-May) and high-use (mid-May                fingerlings could be produced in ponds throughout the year,
             through mid-November) seasons before and after stocking were            and the potential for improving the red drum fishery through
             compared for fish >450 min total length. Relative abundance             stocking could be examined.
             and angler landings of red drum were higher after stocking in              Enhancement of wild populations through stocking ap-
             the stocked bay; abundance and angler landings were similar             peared feasible. Historic bag seine and trammel net collec-
             or lower in unstocked bays after the stocking dates. Additional         tions indicated the habitat could support more red drum than
             research is needed to determine optimum stocking rates, times,          were present in the 1970s (Matlock 1984). A preliminary
             and fish sizes.                                                         evaluation of a limited stocking indicated that stocked fish
                                                                                     survived, grew, and supplemented the juvenile population
                                                                                     in the stocked bay (Matlock et al. 1986). However, too few
                                                                                     fish were stocked to detect any impact on recruitment to the
                                                                                     fishery.
                                                                                        These initial results were sufficient to convince sport fish-
                                                                                     ermen, a major electric utility company, and the Texas Legis-
                                                                                     lature that a red drum hatchery could be beneficial. The Gulf
                                                                                     Coast Conservation Association donated $1.4 million to build
                                                                                     the facility (Rutledge and Matlock 1986), Central Power and
                                                                                     Light Company provided the land, and the Texas Legislature
                                                                                     appropriated about $160,000 operating expenses for staff and
                                                                                     equipment. The hatchery was designed to produce about 10
                                                                                     million fingerlings annually from 8 ha of earthen ponds. In
                                                                                     each of the first 3 years of operation (1983-85), 7 to 9 million
                                                                                     fingerlings were produced (McCarty et al. 1985, Matlock
                                                                                     1986). However, the impact of these stockings on sport
                                                                                     angler landings has not been determined.
                                                                                        The objective of this paper is to present a preliminary
                                                                                     assessment of the success of 2 years of stocking red drum
                                                                                     fingerlings into two Texas bays.







                 Materials and methods


                 Red drum fingerlings (11-83 min TL) were spawned and
                 reared in earthen ponds (0.8 ha) at the John Wilson Marine                                                        HOUSTON
                 Fish Hatchery (McCarty et al. 1985). Fish were transported                                 XAS
                                                                                                          TE
                 to stocking sites (Fig. 1) in trailers fitted with a three-charnber                                                             SABINE.L.AkE
                 tank (3.0 X 1.2 X 0.8 in) that was supplied with compressed                                                                 GALVESTON SAY
                 oxygen to maintain 4-10 ppm (Hammerschmidt and Saul
                 1985). Each chamber held about 1,950 L of water and con-
                 tained 10 ppm furacin.                                                                                         EMT MATAGORDA SAY
                   Fish were either stocked directly into the bay or transferred
                 through a plastic pipe to tanks on a barge by gravity flow                                             MATAGORDA RAY
                 and then transported to stocking sites. Fish were acclimated                                      SAN ANTONIO SAY
                 to ambient water temperature and salinity (ï¿½ 2'C and 5 ppt)                                    ARANSAS RAY
                 at each site by exchanging water in the tanks at a rate of about           CORPUS CHRISTI   CORPUS CHRISTI BAY               4.
                 2,600 L/h. Release mortality was estimated for each load                                                                GULF OF MEXICO
                 by holding 25 fish in each of 3 or 4 cages for 24 hours at                               UPPER LAGUNA MADRE
                 the release site (Hammerschmidt and Saul 1985).
                   About 14 million fish were released in 1983, late 1984,
                 and early 1985 into the San Antonio and Corpus Christi Bay
                 systems (Fig. 1). The San Antonio Bay system received 2.3
                 million fish in May 1983 and 6.0 million fish in May and                                    LOWER LAGUNA MADRE
                 July 1984 (Matlock 1986). The Corpus Christi Bay system                  rIRO NSVILLE
                 received 4.7 million fish in September and November 1983
                 and 250,000 in January 1985. The objective of these releases                  AEXICO
                 was to increase significantly (P = 0. 10) the number of red
                 drum landed by sport-boat anglers over the historic harvest
                 in these two bay systems. These two bays were selected                                                Figure 1
                 because they have diverse habitats and fishing pressures, no             Bay systems of Texas coast. Red drum were stocked in the San Antonio
                 netting is allowed, the ratio of surface area to number of                                and Corpus Christi Bay systems.
                 anglers was among the lowest on the coast, and the historic
                 landing rates for red drum were among the highest on the
                 coast. These characteristics should have maximized the prob-             Results and discussion
                 ability of determining if the objective was met. They would
                 also allow the inference that if stocking was effective in these         Stocked fish survived the stocking process very well. The
                 bays, then it should be effective in all other bays where                mean (ï¿½ I SE) 24-hour survival of fish held in cages was
                 historic landing rates were less.                                        89.4- ï¿½ 2.7 % in 1983 and 86.2 ï¿½ 2.2 % in 1984 @Hanimer-
                   The effect of stocking was measured in four ways. Cage                 schmidt and Saul 1985, Hammerschmidt 1986). Juvenile fish
                 studies (described previously) were used to determine ini-               were recaptured in bag seines in both stocked bay systems
                 tial survival after stocking. Bag seines were pulled at stock-           for tip to 1.5 months after stocking (Dailey and McEachron
                 ing sites for <3 months after stocking to determine longer-              19815). Thereafter, fish were large enough to escape bag
                 term survival (>O %). Ongoing surveys of sport-boat anglers
                 (Osburn and Ferguson 1986) and fishery-independent moni-                 seines (Matlock 1984).
                 toring with gill nets (7.6, 10.2, 12.7, and 15.2 cm stretched               Stocking appears to have increased the number of red drum
                 meshes) in the two stocked bays and one unstocked bay                    available for harvest in Texas bays. However, this impact
                 (Crowe et al. 1986) were used to measure changes in anglers'             was not consistent among all stockings because of a major
                 landings and red drum relative abundance. Trends in mean                 fish kill caused by record-breaking freezing temperatures dur-
                 landing rates in stocked bays were compared with the un-                 ing late December 1983 and early January 1984 (McEachron
                 stocked bay.                                                             et al. 1984). Over 90,000 red drum were killed coastwide,
                                                                                          and most of the dead fish were found in the San Antonio
                                                                                          Bay system. The mean catch rates in gill nets in the stocked
                                                                                          Corpus Christi Bay system were much higher in the 2 years
                                                                                          after stocking than in the years before stocking (Fig. 2). Mean
                                                                                          catch rates in the upper Laguna Madre (control) were also
                                                                                          higher after stocking, but were not as great as in the stocked
                                                                                          bay. The increased catches in fall 1984 and 1985 in the
                                                                                          stocked bay were primarily in the 7.6-cm stretched mesh,

                                                                                      12








                    0.8                                                                                       0.6                               STOCKED

                                    STOCKED                                                                                                      UNSTOCKED

                                    UNSTOCKED                                                                                                        7.6 cm
                                                                                                              0.4

                    0.6



                                                                                                              0.2-


                    0.4
               Z

                                                                                                          LU
               Z                                                                                                    M11-1                       I L
                                                                                                                 0+


                                                                                                              0.4                                    10.2 cm
                    0.2
                                                                                                          Z



                                                                                                              0.2
                                                                   wom-    I

                               FALL     FALL     FALL    SPRING     FALL   SPRING
                               .75-'82   .83                        Ts       Te

                                                                                                                 0
                                            Figure 2                                                          0.2.                                   12.7 c.
              Mean catch rate (no./h) of red drum in gill nets in the Corpus Christi
              Bay (stocked) and upper Laguna Madre (unstocked) systems in fall (Sept-
              Nov) and spring (April-June) during 1983-86. The historic mean fall
              catch rate (for the period 1975-83) is also shown. Stocking occurred                                   U F -fl
                                                                                                                 0
                   in fall 1983 (4.7 million fish) and January 1985 (250,WO).                                         FALL    FALL   SPRING   FALL   SPRING
                                                                                                                       '83                     as      .1


                                                                                                                             Figure 3
              but this pattern did not occur in the unstocked bay (Fig. 3).                            Mean catch rate (no./h) of red drum in the 7.6, 10.2,
              This reflects recruitment of stocked fish to the 7.6-cm                                  and 12.7 cm stretcbed-mesh portions of gill nets in the
                                                                                                       Corpus Christi Bay (stocked) and upper Laguna
              stretched mesh I year after each stocking. The stocked fish                              Madre (unstocked) systems, fall (Sept-Nov) and spring
              were evident in each subsequent season in the larger mesh                                (April-June), during 1%3-86. Stocking occurred in fall
              portions of gill nets. In the San Antonio Bay system, the mean                                               1983 and 1984.
              catch rate in gill nets decreased after the 1983 stocking, but
              increased after the 1984 stocking (Fig. 4). Apparently very
              few of the 2.3 million fish stocked in 1983 survived this
              freeze. The mean catch rate in gill nets in spring 1984 (0.2                    bay, but it declined in the unstocked bay. The number of
              fish/h) was among the lowest recorded since 1975 (Fig. 4).                      red drum landed from the stocked bay also increased 100%
              However, wild fish may have been more affected than                             over the historic mean in 1985-86 (Fig. 6). Landings in the
              stocked fish. The mean catch rate of age-1 wild fish, those                     unstocked bay increased only 27 % from the historic mean,
              in the 7.6-cm stretched mesh part of the nets, declined to                      although anglers fished 45 % more man-hours in the un-
              the lowest level ever (<I fish/h), while catches in the larger                  stocked bay than in the stocked bay in 1985-86 (882 vs. 609
              meshes did not decline. Fish stocked in July 1984 were first                    man-hours). The increased landings over the historic mean
              apparent in gill nets in fall 1985, and the mean catch rate                     in the upper Laguna Madre (18,500 vs. 14,600 fish, respec-
              in gill nets was the third highest on record (Fig. 4). Most                     tively) would have been much less than 27% had the un-
              (83%) of this catch was in the 7.6-cm stretched mesh.                           usually low 1984-85 landings (3,800 fish) not been included
                Stocking apparently increased the fishing success of sport-                   in calculating the historic mean. Annual landings in all other
              boat anglers for red drum. The mean landing rate by these                       years in the upper Laguna Madre were 13, 100 to 25,700 fish
              fishermen increased 150% over the mean historic (1979-84)                       and averaged 16,800 fish.
              rate in the stocked Corpus Christi Bay system in the high-
              use (15 May-15 November) season of 1985 (Fig. 5) when
              stocked fish reached the minimum legal size limit of 457 mm.
              The mean landing rate also increased in the unstocked upper
                                                MRS                 9
                                                OR
                                                OR






                                                                                                                                             m















































              Laguna Madre, but by only 50 %. The mean landing rate in
              the following low-use season (16 November-14 May) in
              1985-86 was similar to the historic catch rate in the stocked



                                                                                         13












                            





                            



                                                                         



                            





                            

                                                                                                                                        Figure 4
                                                                                                                   Mean catch rate (no./h) of red drum in gill nets in the
                                                                                                                  San Antonio Bay system, fall (Sept-Nov) and spring (April-
                                                
                                                                                                                  June), during 1975-86. Arrows indicate dates of major
                                                         										events affecting red drum. Fish were stocked in spring
                                                                                                                  1983 (2.3 million) and in summer 1984 (6.0 million).













                            
                                                  Figure 5
                     Mean landing (catch) rate (no./man-hour) of red drum landed by                                              Figure 6
                     sportboat anglers in the Corpus Christi Bay (stocked) and upper                     Number of red drum landed annually (15 May-14 May) by
                     Laguna Madre (unstocked) systems before and after fish reached                      sportboat anglers in the Corpus Christi Bay (stocked) and
                     minimum size limits of 457 mm TL in the high-use (15 May-20 Nov)                    upper Laguna Madre (unstocked) systems before and after
                            and low-use (21 Nov-14 May) season during 1979-86.                           stocked fish reached minimum size limit of 457 mm TL.





                      Stocking also benefited anglers in the San Antonio Bay                        as the historic mean (6,200 fish) although effort (36,200 man-
                   system. Although the 1983-84 freeze greatly reduced the                          hours) was about 50% less. Fish stocked in 1984 are just
                   number of available fish, the anglers' mean landing rate                         now becoming retainable by fishermen.
                   increased from the 1982-83 low-use season in the San An-                          Wild stocks of red drum can be enhanced through stock-
                   tonio Bay system in that low-use season when stocked fish                        ing to provide improved fishing success. However, the
                   became retainable by anglers (Table 1). The mean catch rate                      degree of improvement depends on such factors as the carry-
                                                                    





















                   also increased in the adjacent Matagorda Bay system; some                        ing capacity of each system, the number of wild fish present
                   fingerlings may have moved to this system. Mean landing                          before stocking, fishing pressure, harvest restrictions, and
                   rates in other bays either remained the same, decreased, or                      climatic events. The sale of red drum caught in Texas was
                   remained less than 0. 1 fish/man-hour. Landings during the                       prohibited 2 years before stocking the Corpus Christi Bay
                   low-use 1984-85 season (5,800 fish) were about the same                          system. About 3 months after the first stocking, the Texas

                                                                                              14
 








                                                                                          Table 1
                                       Mean catch rate (no./man-hour) of red drum landed by private sport-boat anglers in Texas bay systems
                                                         during the low-use (21 Nov-14 May) seasons, 1982-83 and 1983-84.

                                                                                                                                  Upper         Lower
                                                                                          San                        Corpus       Laguna       Laguna
                                         Year         Galveston       Matagorda        Antonio        Aransas        Christi      Madre         Madre

                                        1982-83          0.01            0.03             0.04          0.07         <0.01         0.01          0.05
                                        1983-84          0.01            0.07             0.13          0.06           0.05        0.01          0.04




               coast experienced the worst freeze in history. The minimum                          Citations
               size limit was increased from 406 to 457 mm, and the bag
               and possession limits were reduced by 50%. The existing                             Arnold, C.R., J.D. Williams, A. Johnson, W.H. Bailey, and J.L.
               and subsequently imposed restrictions reduced the impact of                           Lasswell
               the freeze on red drum. Fishing improved in the upper                                    1977 Laboratory spawning and larval rearing of red drum and south-
                                                                                                          ern flounder. Proc. Annu. Conf. S.E. Assoc. Fish Wildl. Agen-
               Laguna Madre even without stocking; however, this im-                                      cies 31:437-441.
               provement was even greater with stocking.                                           Colurn, R.L., B.T. Hysmith, and R.E. Stevens
                  Additional research is needed to determine optimum stock-                             1976 Fingerling production of striped bass (Morone saxatilis), spotted
               ing rates. An intensive stocking of fish marked with coded                                 seatrout (Cynoscion nebulosus), and red drum (Sciaenops ocellata)
                                                                                                          in saltwater ponds. Proc. World Maricult. Soc. 7:79-92.
               metal tags or genetically marked fish could be used to im-                          Crowe, A.L., L.W. McEachron, and P.C. Hammerschmidt
               prove estimates of natural mortality rates and the contribu-                             1986 Trends in relative abundance and size of selected fitifish in Texas
               tion of stocked fish to the wild stocks and angler harvest.                                bays: November 1975-December 1985. Tex. Parks Wildl. Dep.,
                 These preliminary results are not based on a rigorous                                    Coast. Fish. Br. Manage. Data Ser. 114, Austin, TX, 259 p.
               statistical analysis of the data collected. The landings data                       Dailey, J.A., and L.W. McEachron
               have not been adjusted for changes in minimum size limits                                1986 Survival of unmarked red drum stocked into two Texas bays.
                                                                                                          Tex. Parks Wildl. Dep., Coast. Fish. Br. Manage. Data Ser. 116,
               or bag and possession limits. Therefore, the conclusions                                   Austin, TX, 8 p.
               presented are conservative. A more rigorous analysis is                             Hamwerschmidt, P.C.
               planned after the 5-year project ends in 1988 and all stocked                            1986 Initial survival of red drum fingerlings stocked in Texas bays
               fish have left the estuarine fishery.                                                      during 1984-1985. Tex. Parks Wildl. Dep., Coast. Fish. Br.
                                                                                                          Manage. Data Ser. 106, Austin, TX, 14 p.
                                                                                                   Hammerschmidt, P.C., and G.E. Saul
                                                                                                        1985 Initial survival of red drum fingerlings stocked in Texas bays
                                                                                                          during 1983. Annu. Proc. Tex. Chap. Am. Fish. Soc. 7:13-28.
                                                                                                   Matlock, G.C.
                                                                                                        1980 History and management of the red drum fishery. Proc. Gulf
                                                                                                          States Mar. Fish. Comm., Publ. 5, Ocean Springs, MS, 37-53.
                                                                                                        1984 A basis for the development of a management plan for red drum
                                                                                                          in Texas. Ph.D. diss., Texas A&M Univ., College Station, TX,
                                                                                                          291 p.
                                                                                                        1986 A summary of 10 years of stocking fishes into Texas bays. Tex.
                                                                                                          Parks Wildl. Dep., Coast. Fish. Br., Manage. Data Ser. 104, Austin,
                                                                                                          TX, 19 p.
                                                                                                   Matlock, G.C., R.J. Kemp, Jr., and T.L. Heffernan
                                                                                                        1986 Stocking as a management tool for a red drum fishery, a pre-
                                                                                                          liminary evaluation. Tex. Parks Wildl. Dep., Coast. Fish. Br.,
                                                                                                          Manage. Data Ser. 75, Austin, TX, 27 p.
                                                                                                   McCarty, G.E., J.G. Geiger, L.N. Sturmer, B.A. Gregg, and W.P.
                                                                                                     Rutledge
                                                                                                        1985 Marine finfish culture in Texas-Model for the future. Proc.
                                                                                                          World Maricult. Soc. 15:120-131.
                                                                                                   McEachron, L.W., G. Saul, J. Cox, C.E. Bryan, and G. Matlock
                                                                                                        1984 Fish kill. Tex. Parks Wildl. Mag. 42(4):11-13.
                                                                                                   Osburn, H.R., and M.O. Ferguson
                                                                                                        1986 Trends in finfish landings by sport-boat fishermen in Texas
                                                                                                          marine waters, May 1974-May 1985. Tex. Parks Wildl. Dep.,
                                                                                                          Coast. Fish. Br., Manage. Data Ser. 90, Austin, TX, 448 p.
                                                                                                   Rutledge, W.P., and G.C. Matlock
                                                                                                        1986 Mariculture and fisheries management-A future cooperative
                                                                                                          approach. In Stroud, R.H. (ed.), Fish bulture in fisheries manage-
                                                                                                          ment, p. 119-127. Proc., Int. Symp. on Use of Culture in Fisheries
                                                                                                          Management. Am. Fish. Soc., Bethesda, MD.
                                                                                              15





             Genetic Marking and                                                         Individuals from discrete subgroups within a species usual-
             Ocean Farming'                                                              ly lack readily visible characters (or marks) that permit
                                                                                         subgroup classification. More subtle distinguishing char-
                                                                                         acteristics sometimes become apparent through specialized
                                                                                         procedures, and various methods have been devised to im-
             FRED M. UTTER                                                               pose identifiable attributes on individuals within a group (i.e.,
             Coastal Zone and Estuarine Studies                                          marking). Most commonly used marks are restricted to the
             Northwest Fisheries Center                                                  immediate generation because they are largely or entirely
             National Marine Fisheries Service, NOAA                                     not heritable.
             2725 Montlake Boulevard East                                                   Completely heritable characters, particularly allelic pro-
             Seattle, Washington 98112                                                   tein genes detected by electrophoresis, have proven to be
                                                                                         valuable genetic marks. Previously unknown genetically
             JAMEES E. SEEB;                                                             isolated subgroups of many fishes have been identified
             Department of Zoology                                                       (Allendorf et a]. 1987). This information has been used to
             Southern Illinois University                                                monitor migrations of distinct groups in stock mixtures (e.g.,
             Carbondale, Illinois 62901                                                  Milner et al. 1985). Natural genetic differences between
                                                                                         populations have been used to estimate proportions of stocked
                                                                                         and unstocked fish in specific fisheries (e.g., Murphy et al.
                                                                                         1983).
                                                                                            Intentional breeding using distinct genotypes (i.e., genetic
                                                                                         marking) has been used to create identifiable groups. Ex-
                                                                                         perimental applications of genetically marked groups have
                                                                                         included measurements of growth and survival of wild,
                                                                                         hatchery, and hybrid steelhead in different environments
                                                                                         (Reisenbichler and McIntyre 1977), quantifying contributions
                                                                                         of chum salmon males of different behavioral states (Schroder
                                                                                         1982), and identifying differing fertilization rates of sperm
                                                                                         from individual pink salmon males examined under varying
                                                                                         conditions (Gharrett and Shirley 1985).
                                                                                            Genetically marked populations have also been created and
                                                                                         monitored. Two concerns that must be met if the marked
                                                                                         populations are to approximate the long-term performance
                                                                                         potential of the parent stock are (1) a negligible effect on
                                                                                         performance of individuals having different genotypes for
                                                                                         the alleles involved in the marking process, and (2) an ade-
                                                                                         quate sampling of genes over all loci from the parent stock
                                                                                         in the marked population. Guidelines relating to the first con-
                                                                                         cern are listed below:
                                                                                            I Be particularly cautious of variants where good evidence
                                                                                         for selection has been indicated in other organisms for par-
                                                                                         ticular protein classes.
                                                                                            2 Seek variants that occur widely and in diverse environ-
                                                                                         ments.
                                                                                            3 Be careful of rare alleles or those with substantial fre-
                                                                                         quencies in restricted environments.
                                                                                            4 Monitor the performance of comparable marked and
                                                                                         unmarked individuals and populations.
                                                                                            The second concern relates to the effective numbers of
                                                                                         breeding individuals in the founding populations and in sub-
                                                                                         sequent generations. Guidelines (suggested by Allendorf and
               'The information in this extended abstract is included in the following   Ryman 1987) include:
             article: Utter, F.M., and J.E. Seeb. In press. Genetic marking in fishes:      1 Use 25 individuals of each sex (with equal contribu-
             Overview focusing on protein variation. Trans. Am. Fish. Soc.               tions from individual matings) as an absolute minimum for
                                                                                         establishing a new population.

                                                                                     17







                      2 Use a considerably larger number of individuals for                          Citations
                   maintenance of established populations.
                      Two projects involving Pacific salmon species demonstrate                      Allendorf, F., and N. Ryman
                   somewhat different applications of genetically marking pop-                            1987 Genetic management of hatchery stocks. In Ryman, N., and
                   ulations. A segment of a chum salmon run to a stream in                                  F. Utter (eds.), Population genetics and fishery management, p. 141-
                   Puget Sound, Washington, USA, was genetically marked for                                 159. Univ. Wash. Press, Seattle.
                                                                                                     Alleindorf, F., N. Ryman, and F. Utter
                   five consecutive years using males having selected genotypes                           1.987 Genetics and fishery management: Past, present, and future. In
                   for two enzyme systems mated with randomly chosen females                                Ryman, N., and F. Utter (eds.), Population genetics and fishery
                   (Seeb et al. 1986). Allele frequency differences between                                 management, p. 1-20. Univ. Wash. Press, Seattle.
                   marked groups and the parent population (10% or greater                           Ferris, S.D., and W.J. Berg
                   for both enzyme systems) resulted in estimates of enhance-                             IL987 The utility of mitochondrial DNA in fish genetics and fishery
                                                                                                            management. In Ryman, N., and F. Utter (eds.), Population genetics
                   ment contributions to the total returning adult populations                              and fishery management, p. 277-299. Univ. Washington Press,
                   in the stream from 6% to 29%. Dilution of the mark in the                                Seattle.
                   adjacent inlet resulted in estimates between 2.2 and 4.3                          Gharrett, A.J.
                   million juvenile fish.                                                                 11985 Genetic interaction of Auke Creek Hatchery pink salmon with
                      Late-returning segments of even- and odd-year runs of pink                            natural spawning stocks in Auke Creek. Rep. SFS UAJ-8509, Univ.
                                                                                                            Alaska, Juneau, 40 p.
                   salmon were genetically marked for four consecutive years                         Gharrett, A.J., and S.M. Shirley
                   at a hatchery on a stream near Juneau, Alaska, USA (Lane                               :1985 A genetic examination of spawning methodology in a salmon
                   1984, Gharrett 1985); different single enzyme marks were                                 hatchery. Aquaculture 47:245-456.
                   used for even- and odd-year runs. Both males and females                          Gyllensten, U.
                   were selected for breeders, permitting a much larger change                            1985 The genetic structure of fish: Differences in the intraspecific
                                                                                                            distribution of biochemical genetic variation between marine, anad-
                   of allele frequency between the parent and marked popula-                                romous, and freshwater species. J. Fish. Biol. 26:691-699.
                   tions. No straying to adjacent drainages was detected for                         Lane, S.
                   either year-class. Evidence of straying within the drainage                            1984 The implementation and evaluation of a genetic mark in a
                   of the parent population was observed only for the late seg-                             hatchery stock of pink salmon (Oncorhynchus gorbuscha) in south-
                   ment of the even-year run both upstream and downstream                                   east Alaska. MS thesis, Univ. Alaska, Juneau, 107 p.
                                                                                                     Milner, G., D. Teel, F. Utter, and G. Winans
                   from the hatchery.                                                                     1985 A genetic method of stock identification in mixed populations
                      Genetic marking       projects similar to those summarized                            of Pacific salmon, Oncorhynchus spp. Mar. Fish. Rev. 47(l):1-8.
                   above are feasible       for any cultured population. Cultured                    Murphy, B.R., L.A. Nielsen, and B.J. Turner
                   marine species are particularly suitable for genetic marking;                          1983 Use of genetic tags to evaluate stocking success for reservoir
                   their generally reduced genetic divergence relative to fresh-                            walleyes. Trans. Am. Fish. Soc. 112:457-463.
                                                                                                     Reisenbichler, R.R., and J.D. McIntyre
                   water and anadromous species (Gyllensten 1985) makes                                   1977 Genetic differences in growth and survival of juvenile hatchery
                   marked populations more readily apparent amidst a more                                   and wild steelhead trout, Salnw gairdneri. J. Fish. Res. Board Can.
                   uniform background. Genetic marking can also be extended                                 34:123-128.
                   to wild populations, providing potential breeders can be inter-                   Schroder, S.L.
                                                                                                          1982 The influence of intrasexual competition on the distribution of
                   cepted, genotyped, and only those of appropriate genotype                                chum salmon in an experimental stream. In Brannon, E.L., and E.O.
                   permitted to spawn.                                                                      Salo (eds.), Salmon and trout migratory behavior symposium, p.
                      Genetic marking provides a heritable brand with diverse                               275-285. Coll. Fish., Univ. Wash., Seattle.
                   uses. Marked populations permit monitoring of intermingling                       Seeb, J., L. Seeb, and F. Utter
                   and interbreeding with other populations. This capability                              1986 Use of genetic marks to assess stock dynamics and management
                   relates to environmental and genetic concerns about inten-                               programs for chum salmon. Trans. Am. Fish. Soc. 115:448-454.
                   tional or accidental releases of cultured or transplanted
                   populations. Conversely, genetically marked populations can
                   be used by their owners or stewards for identification in
                   mixed harvests.
                      Although protein coding genes are presently the most
                   useful source of materials for genetic marking, they repre-
                   sent less than 1 % of the total DNA of an organism. Much
                   additional genetic variation exists that is potentially useful
                   for genetic marking. The DNA of mitochondria is a source
                   of variation that is finding increasing application as a popula-
                   tion marker (e.g., Ferris and Berg 1987). Immunologically
                   detected genetic markers are another souce of variation that
                   may be useftil. The same principles concerning the perfor-
                   mance of genotypes and the adequacy of effective popula-
                   tion size pertain to any genetic mark that is used.


                                                                                                18






              Culture of North American                                                       Sturgeons can be considered "living fossils," exhibiting little
                                                                                              change from their sturgeon-like ancestors of the upper Creta-
              Sturgeons for Fishery                                                           ceous period, 100 million years ago. Worldwide, there are
                                                                                              25 species of sturgeons, 18 of the genus Acipenser, two of
              Enhancement'                            2                                       the genus Huso (which contains the largest sturgeon), two
                                                                                              shovelnose sturgeons (Scaphirhynchus), and three of the
                                                                                              genus Pseudoseaphirhynchus. In North America, there are
                                                                                              eight species inhabiting various freshwater and/or coastal
              THEODORE Q. SNUTH                                                               habitats (Table 1). Of these, Atlantic sturgeon Acipenser
              South Carolina Wildlife and Marine Resources Department                         oxythynchus, lake sturgeon A. fidvescens, shortnose sturgeon
              P.O. Box 12559                                                                  A. brevirostrum, white sturgeon A. transmontanus, and
              Charleston, South Carolina 29412                                                paddlefish Polyodon spathula, have received substantial
                                                                                              interest in recent years for purposes ranging from stock
                                                                                              enhancement to commercial aquaculture.
                                                                                                Historically, sturgeons were important to early settlers and
              ABSTRACT                                                                        served as an item of commerce. Reports and books in colonial
                                                                                              days often contained information on the abundance of these
              North American sturgeons were important to early colonists,                     awesome creatures which the indians named "Mishe-
              and about 1860 large-scale exploration was initiated. However,                  Nahma" or "King of Fishes." Large-scale commercial ex-
              by the turn of the century, most sturgeon stocks were severely                  ploitation of North American sturgeon stocks began during
              depleted and the major fisheries collapsed. Early fishery man-                  the last quarter of the 19th century. The rapidity with which
              agers sought to rehabilitate the stocks through propagated fish,                the major stocks were depleted astonished fishermen and
              but suitable culture efforts could not be developed and efforts                 fishery managers. The statement by Tower (1909) typifies
              were abandoned by about 1910.
                In recent years, protection of some sturgeon stocks has re-                   the thoughts and feelings of the time-"It seems scarcely
              sulted from enactment of controlled fishing regulations and/or                  comprehensible that a fish so widely distributed through the
              listing species as an endangered species. Renewal interest has                  country, so abundant, and so little used less than three
              focused on spawning and culture of most North American stur-                    decades ago, has so rapidly disappeared that the end is
              geons, and today there are small-scale stocking efforts under-                  already in sight. " This overutilization of the sturgeons as
              way with several species.                                                       well as other natural resources was responsible for the ini-
                                                                                              tiation of a conservation movement around 1907. Such con-
                                                                                              servation efforts, however, came too late to have any signifi-
                                                                                              cant impact on the sturgeons.
                                                                                                Today, only remnant populations remain of most major
                                                                                              North American stocks of sturgeons,, and their geographic
                                                                                              ranges have been sharply reduced from those of only 100
                                                                                              years ago. The purpose of this report is to briefly review
                                                                                              the early and current sturgeon fisheries and to discuss the
                                                                                              culture efforts for fishery enhancement of North American
                                                                                              sturgeons, focusing on the more important Atlantic, lake,
                                                                                              shortnose and white sturgeons, and the paddlefish.


                                                                                              Exploitation of sturgeons

                                                                                              Early fisheries
                                                                                              Utilization of North American sturgeons varied according
                                                                                              to species, area, and time. During the early to mid-19th cen-
                                                                                              tury, sturgeons were not highly regarded. At this time, they
                                                                                              were intentionally killed to reduce damage to fishing nets,
                                                                                              fed to livestock, used as fertilizer and to fuel boilers of steam-
                                                                                              boats (Harkness and Dymond 1961, Galbreath 1985). How-
                                                                                              ever, sturgeons eventually became highly prized and were
                'Contribution No. 219 from the South Carolina Marine Resources Center.        valued as the most expensive freshwater fish. Large-scale
                2Preparation of this report was supported by the U.S. Fish and Wildlife       exploitation began around 1860 when it was learned that
              Service, Contract Number S.C. -AFS- I I and the State of South Carolina.        smoked sturgeon could be substituted for smoked halibut and

                                                                                         19








                                                                                                 Table I
                                                         Geographical distribution and general habitat of North American sturgeons.

                           Species                 Common name                                Geographical distribution                                        Habitat

                      Acipenser
                       brevirostruln            Shormose sturgeon            Atlantic coast from St. John River, New Brunswick, Canada,          Anadromous; large coastal rivers
                                                                             to St. Johns River, east coast of Florida
                       fulvescens               Lake sturgeon                Mississippi River, the Great Lakes, and the Hudson Bay              Freshwater; lakes and large rivers
                                                                             drainage basins
                       medirostris              Green sturgeon               Pacific coast from Gulf of Alaska. south to North Baja, Cali-       Anadromous; primarily estuarine
                                                                             fornia, especially the Columbia River
                       oxyrhynchus              Atlantic sturgeon            Atlantic coast from Labrador through Gulf of Mexico to              Anadromous; primarily estuarine
                                                                             northern coast of South America
                       transnzontanus           White sturgeon               Pacific coast forn Gulf of Alaska. south to north Baja, Cali-       Anadromous or semi-anadromous;
                                                                             fornia, especially Columbia River and Sacramento-San                large flowing rivers
                                                                             Joaquin system
                      Scaphirhynchus
                       albus                    Pallid sturgeon              Mississippi River from Minois south to Louisiana, Missouri          Freshwater; large turbid flowing
                                                                             River from Montana to Missouri                                      rivers
                       platorhynchus            Shovelnose sturgeon          Ohio, Mississippi, and Missouri Rivers; Mobile Bay drain-           Freshwater; large turbid flowing
                                                                             age, Alabama River, Rio Grande in Texas and New Mexico              rivers
                      Polydon spathula          Paddlefish                   Mississippi River system, Mobile Bay drainage, Alabama              Freshwater; backwaters, sluggish
                                                                             River west to east Texas                                            pools, bayous, oxbows of large
                                                                                                                                                 rivers and lakes





                   that the eggs could be made into high-quality caviar. Besides                         kg (Galbreath 1985). Similarly, landing of lake sturgeon
                   these products, isinglass was derived from the swim blad-                             peaked around 1885 (2.3 million kg smoked flesh; 1,000 kegs
                   der and cartilagenous backbone of sturgeons and used to                               caviar; 1,400 kg isinglass) and then suffered a similar decline
                   clarify liquids and stiffen jams and jellies; fish oil could be                       (Harkness and Dymond 1961). Commercial harvesting of
                   rendered from the flesh and used in paints; and leather was                           paddlefish became important after the lake sturgeon stocks
                   made from the skin. However, the main products were the                               were depleted. By 1899, landings of paddlefish had increased
                   flesh and the caviar, as is the case today.                                           to 1. 1 million kg from 0.47 million kg in 1894. Like the
                      Generally, sturgeon fishing occurred during the spring as                          Acipenseridae, paddlefish landings decreased shortly after
                   adults migrated to freshwater spawning areas, although some                           large-scale exploitation began, but the decline was not as
                   species, such as the, white sturgeon, were harvested on their                         precipitous nor as drastic as that of the other sturgeons
                   feeding grounds as well. A variety of gear was employed,                              (Gengerke 1986). In 1922, landings of paddlefish were still
                   including harpoons, grapple hooks, baited and unbaited fish                           0.63 million kg, and over the next 43 years landings ranged
                   hooks, and pound nets, trammel nets, weirs, stake row nets,                           froni 0.27 million kg (1960) to 0.43 million kg (1975).
                   seines, and gill nets. Such gear was quite effective on the
                   highly susceptible sturgeons, and in relatively short periods                         Current fisheries
                   of time, usually 5-10 years, major stocks of sturgeons be-
                   came substantially depleted.                                                          Today, commercial harvesting of some North American
                      Landings from the various sturgeon fisheries differed                              sturgeons still occurs; however, landings in the recreational
                   somewhat, but the pattern of exploitation was always similar                          fishery often exceed commercial landings. The Atlantic
                   (Fig. 1). Landings increased rapidly over a relatively short                          sturgeon has a broad geographical range, yet commercial
                   period during initial exploitation, then declined sharply and                         harvesting is currently restricted to Canada, New York,
                   remained at low levels. Primary fishing emphasis was on                               North Carolina, and Georgia, where only nominal landings
                   the Atlantic sturgeon (including the much smaller shortnose                           are reported (Smith 1985). Formerly, landings in South
                   sturgeon), the white sturgeon, and the lake sturgeon. Land-                           Carolina were substantial relative to total U.S. landings, but
                   ings of Atlantic sturgeon peaked about 1890 with landings                             in recent years the fishery suffered major declines (Smith
                   of 3.3 million kg, but by the turn of the century all major                           et al. 1984) resulting in an indefinite closure of the fishery.
                   fisheries exhibited substantial declines or total collapse                            All existing Atlantic sturgeon fisheries in the United States
                   (Murawski and Pacheco 1977, Smith 1985). In 1892, a peak                              should be closed to protect the remaining stocks. Harvesting
                   production of about 2.5 million kg of white sturgeon was                              of flhe sympatric shortnose sturgeon in the United States has
                   recorded from the Columbia River. However, by 1899 the                                been banned since 1972 when it was listed as an endangered
                   fishery had collapsed and landings were only about 50,000                             species by the U.S. Fish and Wildlife Service (Miller 1972).

                                                                                                   20







                                                                                      Landings of white sturgeon from the lower Columbia River
                      3-                                                            (below the Bonneville Dam) in Washington and Oregon are
                                                                                    now at their highest level since the turn of the century. Most
                                                                 A                  commercial landings result from incidental capture in salmon
                      2-                          Atlantic Sturgeon                 gillnets, although there is some focused fishing for sturgeon
                                                    (Now Jersey fishery)            in certain areas. Recreational hook-and-line fishing for white
                      1                                                             sturgeon in the lower Columbia River has been increasing
                                                                                    steadily, and since 1977 recreational landings have exceeded
                      -                                                             commercial landings. From 1977 to 1983, average commer-
                                                                                    cial landings have been 12,600 fish as compared with 27,300
                                                  7
                      3-                                                            fish for the recreational fisherman (Galbreath 1985). In terms
                                                                                    of total number of fish caught, the landings in 1983 exceed
                co                                               B                  the recorded peak landings in 1892. However, individual fish
                0     2-                                                            weight has declined from a former average size of 68 kg to
                Z                                 Lake Sturgeon
                5     -                             (Lake Erie fishery)             a present weight of 14-16 kg in the commercial fishery and
                Z
                <                                                                   8 kg in the sport catch (Galbreath 1985). Continuing research
                _J    1 -                                                           has established that successful spawning is occurring below
                Z
                0     -                                                             Bonneville Dam, and the consensus is that the white sturgeon
                W
                                                                                    stocks in the lower Columbia River below the Dam are
                M     3-                                                            healthy. A combination of harvest regulations (minimum and
                co                                                                  maximum size limits), increased food supplies, and a shorter
                                                                 C                  salmon gillnet fishing season are primarily responsible for
                      2-                                                            the good condition of the sturgeon stocks. Some harvesting
                                                  White Sturgeon                    of green sturgeon does occur in conjunction with the white
                      -                             (Columbia River fishery)        sturgeon, but their numbers are low and these fish are not
                      1                                                             highly regarded as a food fish. In the upper Columbia River
                                                                                    (above the Bonneville Dam), white sturgeon are essentially
                                                                                    landlocked within each dammed river segment or pool.
                                                                                    Recruitment and stock size appears healthy in some areas,
                      1880   1890      1900      1910    1920      1930             but declines are occurring in others. Additional research is
                                          YEAR                                      needed to assess these various landlocked populations of
                                                                                    white sturgeon.
                                       Figure 1                                       In California, commercial harvesting of white sturgeon has
            Commercial exploitation of various stocks of sturgeons. Data from       been prohibited since 1917 but the sport fishery was reopened
            (A) Murawski and Pacheco 1977, (B) Harkness and Dymond 1%1, and         in 1954. Up to 1963, sturgeon were taken incidentally to
                                   (C) Galbreath 1985.                              fishing for striped bass, Morone saxatilis. However, in 1964
                                                                                    angler success improved dramatically with the use of shrimp
                                                                                    (Crangon spp., Palaemon niacrodactylus) as bait (Kohlhorst
            Similarly, the lake sturgeon is classified as rare over much            1980). Since then, sturgeon have become the focus of an im-
            of its original range by the U.S. Fish and Wildlife Service.            portant sport fishery in the Sacramento-San Joaquin river
            However, this species does support a number of sport                    system. Population estimates suggest that abundance in this
            fisheries, none of which exceeds that in Lake Winnebago,                system decreased between 1967 and 1974, but abundance
            Wisconsin (Folz and Meyers 1985). Harvesting of lake                    has continually increased since then. These changes in
            sturgeon was prohibited from 1916 to 1931, but in 1932 a                population size are believed to be due to variable recruit-
            spear fishing season was established on Lake Winnebago.                 ment rather than to fishing pressure. Currently, it is estimated
            Initially, spear fishermen were allowed to harvest 5 sturgeon           that there are about 130,000 legal-sized adult white sturgeon
            per season, with a minimum length of 76 cm TL, but cur-                 inhabiting this system, of which about 8 % are harvested an-
            rent regulations are more restrictive with only one fish per            nually (David Kohlhorst, Calif. Dep. Fish Game, Stockton,
            season of a 114-cm minimum length allowed. Fishing suc-                 CA, pers. commun., 29 Sept. 1986). No snag fishing is
            cess rate varies from 0.4 to 32.8 % and averages 13.2 %. Dur-           allowed in California and there is a minimum fish size of
            ing 1955-83, harvests ranged from 8 to 2235 fish (1982) (Folz           102 cm (weight -5.4-6.8 kg). Average size of the sport fish
            and Meyers 1985). Based on harvest data and sampling of                 landed is 13-18 kg. Catch records from sturgeon charter boats
                                             @keon
                                                      a Sturg
                                                    (Lake Erie fiherl
                               'L@hlt.                   St.g.. C
                                                    (Columbia River fl



























            spawning fish, it appears that the lake sturgeon stock in Lake          indicate that between 1964 and 1983 the number of anglers/
            Winnebago has not declined since 1955 and that the popula-              year ranged from 1235 to 8284, and the number of fish
            tion is stable or increasing.                                           caught per year ranged from 320 to 2272 (David Kohlhorst,
                                                                                    Calif. Dep. Fish Game, Stockton, CA, pers. commun., 29
                                                                                    Sept. 1986). Landings by charter-boat anglers represent

                                                                               21








                                                                                               Table 2
                          Growth, maturity and longevity of some North American sturgeons. These parameters can vary substantially according to latitude.

                                                                                                                                         Recorded maximum
                                                                           Maturity
                                                                                                                                                             Size
                                                          Age and sex                       Size                        Age
                           Species                            (yr)                        (cm TQ                        (yr)                 (cm TL)                   Wt. (kg)

                      Acipenser
                        brevirostrum                        9-14 (F)'                      57.2-73.3'                     67b                  143  .0b                   23.6b
                                                            8-12  (M)'                         64.2'
                        fulvescens'                       24-26 (F)                            139.7                     152                   240.0                      140.9
                                                           14-16 (M)                           114.3
                        oxyrhynchus                         7-19 (F)d                   173.0-234.   ld                   60'                  426.7f                    368.6'
                                                            5-13  (M)d                  124.6-185.7  d
                        transmontanus                     15-20 (F)9                    168,0-183.09                   >too,                  >610.0'                    675.01
                                                               12  (M)9                        122.09
                      Polyodon spathula                     8-14 (F)'                   148.6-162.8'                      300                  220.0                       90.7i
                                                              2-9                         66.8-117.3

                      'Taubert 1980              'Prelegel and Wirth  1977           'Magnin 1964                           gGalbreath 1985            'Russell 1986
                      bDadswell 1979             dSmith et al. 1982                  'Scott and Crossman 1973               'Galbreath 1979            iBoschung et al. 1983




                   only a fraction of the sturgeon caught and recent total an-                         on historic spawning rivers and widespread industrial pollu-
                   nual catch is estimated to be about 10,000 fish.                                    tion caused elimination or reduction in suitable sturgeon
                      In Idaho, there are catch-and-release sport fisheries for                        habitat (Harkness and Dymond 1961, Leland 1968).
                   white sturgeon in the Snake and Kootenai Rivers. However,
                   recent findings suggest that possible closure of several sec-                       Fishery enhancement
                   tions of the Snake River may be needed because of estimated
                   low population size (Cochnauer et al. 1985).                                        Early stock replenishment efforts
                      In contrast to most Acipenseridae, some populations of
                   paddlefish have actually increased substantially since the turn                     Near the end of the 19th century, fishery managers realized
                   of the century, although other stocks no longer inhabit former                      that the sturgeon fisheries had experienced substantial
                   ranges (e.g., Canadian stocks). In the Mississippi, Missouri,                       declines and that something would have to be done to restore
                   Ohio, and Red Rivers, paddlefish populations have signifi-                          the stocks if the fisheries were to be maintained. Unanimous
                   cantly decreased while increased abundance has been re-                             agreement was reached to rehabilitate the various stocks
                   ported from the Tennessee, Cumberland, and Arkansas                                 through artificial propagation programs (Ryder 1890, Cobb
                   Rivers (Gengerke 1986). Sport fisheries, based almost ex-                           1900, Stone 1900). The first successful spawning of a North
                   clusively on snag fishing, are permitted in 17 states and pro-                      America sturgeon was accomplished on the Hudson River
                   vide landings equal to about 70% of the commercial landings.                        in 1875 by Seth Green and Aaron Marks with the New York
                   Annual harvest rates from sport and commercial fishing on                           State Fish Commission. Working with Atlantic sturgeon
                   the order of 15-20% do not appear to damage most popu-                              fishermen, eggs and milt were removed from ripe fish and
                   lations (Pasch and Alexander 1986).                                                 artificially mixed. Using this approach, about 100,000 young
                                                                                                       were hatched over a two-week period. This early success
                   Reasons for decline                                                                 led to the mistaken belief that sturgeon propagation would
                                                                                                       be an easy task. In 1888, the U.S. Fish Commission began
                   As is evident from the landings data, sturgeons are highly                          spawning activities with the Atlantic sturgeon on the Dela-
                   susceptible to man's activities, despite their large size and                       ware River under the direction of J.A. Ryder (Ryder 1890).
                   extended life span (Table 2). Sturgeons mature at an advanced                       Some limited successes occurred, but obtaining adequate
                   age (8-25 years), demonstrate protracted spawning period-                           numbers of ripe females was a problem. Further, fungal in-
                   icities (2-8 years), and inhabit areas of concommitant use                          festation by Achlya and Saprolegnia often caused loss of the
                   by man (rivers, lakes, estuaries, coastal environments). Con-                       incubating eggs. Subsequent workers attempting to spawn
                   sequently, major population perturbations can be easily ef-                         Atlantic sturgeon encountered similar problems of limited
                   fected by man. In all cases, major stocks of sturgeons were                         availability of ripe broodstock and fungal infections of eggs
                   overexploited by fishing (Harkness and Dymond 1961,                                 (Dean 1894, Meehan 1909, Leach 1920). Early spawning
                   Priegel and Wirth 1977, Galbreath 1985, Pasch and Alex-                             efforts with lake sturgeon also had limited success, although
                   ander 1986, Smith 1985). Additionally, installation of dams                         5 million fry were produced in 1891 and released in the

                                                                                                  22







            Detroit River by the Ohio Game and Fish Commission. Ef-                   niques for all species are still in the "art" stage rather than
            forts continued, but successes were limited to instances in               being a science, and success is highly dependent upon the
            which running ripe females containing ovulated eggs were                  condition and stage of ripeness of wild-caught broodstock.
            captured at the same time as ripe males (Harkness and Dy-                 Of the above species, collection of Atlantic sturgeon brood-
            mond 1961). Unfortunately, such instances were uncommon.                  stock is the most difficult as population numbers are low and
            During 1906-09, efforts were initiated to spawn the much                  spawning areas are poorly known and occur in deep areas
            smaller shortnose sturgeon. This work was conducted at the                of fast moving waters. Further, Atlantic sturgeon do not feed
            Torresdale Hatchery in Philadelphia where ponds were used                 during their spawning migration and thus are not suscepti-
            in an attempt to naturally ripen captive adult shortnose                  ble to hook-and-line capture. Consequently, only limited
            sturgeon (Meehan 1909). In several instances, females ex-                 spawning and culture success has been obtained with Atlan-
            pelling eggs were removed from the ponds and small                        tic sturgeon despite substantial efforts undertaken in South
            numbers of fry were hatched. As before, acquisition of                    Carolina (Smith et al. 1981, Smith and Dingley 1984). In
            simultaneously ripe males and females was a problem.                      contrast, lake sturgeon can be routinely observed in the act
               In spite of the high level of interest, efforts to propagate           of spawning in areas where the current is upwelling and
            sturgeons in the United States were abandoned by 1912. A                  where large rocks, boulders, and broken slabs of concrete
            short time later, Canadian workers initiated culture efforts              have been riprapped at a steep angle into the water (Priegel
            but they also experienced the same problems as previously                 and Wirth 1977). Spawning females are dip-netted, and the
            noted. About 1920, they discontinued their propagation                    free-flowing eggs are removed through a small incision. The
            efforts.                                                                  female is sutured and returned to the water. Similarly, run-
                                                                                      ning ripe males can be dip-netted and their milt stripped by
            Soviet   propagation efforts                                              abdominal compression and used to fertilize the eggs
                                                                                      (Czeskleba et al. 1985). Ripe white sturgeon are captured
            The demonstration that secretions of the pituitary gland could            primarily by baited hook-and-line as they move into spawn-
            be used to induce final ripening of fish gonads (Atz and                  ing areas in the Sacramento River. These fish are induced
            Pickford 1959) led to renewed interest in sturgeon propaga-               to spawn using hormonal injection (usually commercially
            tion, especially in the Soviet Union where overfishing and                available carp pituitaries). Additionally, success has been
            installation of dams had caused declines in sturgeon popula-              obtained in using selected prespawning white sturgeon col-
            tions similar to those in North America. Beginning in the                 lected in San Francisco Bay in the fall. Final maturation was
            early 1960s, a major propagation effort was initiated in the              induced in the spring and the fish were successfully spawned
            Soviet Union based on the use of extracted sturgeon pituitary             (Doroshov et al. 1983). Shortnose sturgeon are listed as an
            glands to induce spawning of ripe sturgeons (Manea 1969).                 endangered species in the United States; therefore, a federal
            Annual production of stockable-size fingerling (1-3 g) is now             permit is required to collect them, In South Carolina, mature
            approximately 60- 100 million fish. Sturgeon fingerlings are              migrating broodstock are obtained from commercial shad
            stocked in river deltas during the summer and recaptured as               fishermen as incidental catch in their gill nets. Like the white
            sexually mature adults after 10-20 years of grow-out in the               sturgeon, these fish can be induced to spawn by injection
            sea (Doroshov and Binkowski 1985). No sea fishing for                     of fish pituitaries (Smith et al. 1985). Paddlefish are cap-
            sturgeon is allowed, and caviar is the main product of this               tured with gill nets within 1-11/2 months of their normal
            sea ranching approach. Based on a survival rate of only                   spawning time and held in hatchery tanks. They are induced
            1-3 %, the annual sturgeon landings in the late 1970s from                to ovulate using paddlefish pituitary glands, although recent
            the Caspian Sea basin was 26,000 mt (metric tons), which                  work with LH-RHa suggests that this hormone may be an
            resulted in the production of 1750 mt of caviar (Doroshov                 excellent substitute (Graham et al. 1986).
            and Binkowski 1985).                                                         Techniques for fertilization and incubation of eggs are
                                                                                      generally similar among the sturgeons. Eggs are removed
            Current North American culture efforts                                    from white sturgeon and lake sturgeon through an abdominal
                                                                                      incision over a short period of time. In contrast, eggs are
            During the past 10 years, there has been renewed interest                 stripped from shortnose sturgeon and paddlefish at 20-60
            in the culture of North American sturgeons. Information on                minute intervals over a long period of time. Sperm is col-
            the life history and ecology of the various species, coupled              lected from the males with a syringe and usually diluted with
            with the use of hormones, has resulted in the spawning of                 water (1: 200) just prior to fertilization to prevent polyspermy.
            Atlantic sturgeon (Smith et al. 1980), shortnose sturgeon                 Eggs and sperm are mixed for about 5 minutes and then a
            (Buckley and Kynard 1981, Smith et al. 1985), lake sturgeon               silt, mud, or clay suspension is added to inhibit adhesion of
            (Avelallemant et al. 1983, Folz et al. 1983, Czeskleba et al.             the eggs. Also, chemical treatments have recently been
            1985), and white sturgeon (Doroshov et al. 1983). Tech-                   developed to eliminate the adhesiveness (Kowtal et al. 1986).
            niques for spawning and rearing paddlefish were developed                 The non-adhesive eggs are incubated in McDonald incubators
            in the mid-1960s and early 1970s, and recently there have                 Oars) for about 5-7 days at a temperature of 14-16'C. Dur-
            been efforts to rear this species for stocking purposes and               ing incubation, eggs are gently rolled with upflow water.
            for caviar production (Graham et al. 1986). Spawning tech-                Upon hatching, the sac-fry swim up and out of the incubators

                                                                                  23







                and are collected in adjacent tanks. After about 10 days, the          stocking programs with this species. During 1986, only 26
                fry begin feeding.                                                     adult Atlantic sturgeon were captured during an 8-week in-
                   Larval and juvenile rearing differs among the various               tensive fishing effort by ex-commercial sturgeon fishermen.
                sturgeons. White and shormose sturgeon can be trained to               Of these, no males were running ripe and no females could
                accept soft-moist and dry diets and are typically reared in            be induced to ovulate. In contrast to Atlantic sturgeon, sig-
                tanks in intensive systems. Survival rate to a small juvenile          nificant progress has been attained in spawning and culture
                size (-30 g, 3-4 months old) is about 15 %. After this size            of shormose sturgeon. Basic spawning techniques have been
                is attained, mortality rarely occurs. Rearing of larval and            developed and fry have been produced during 1984-86.
                juvenile lake sturgeon has been difficult because they appear          Grow-out ofjuvenfles in intensive systems has been success-
                to require live foods (Anderson 1984, Czeskleba, et a]. 1985,          ftil (Smith et al. 1986), and some fish have attained a mature
                Graham 1986a) and attempts to rear this species in fertilized          size (1.8-2.1 kg) after only 18 months of culture. Thus,
                ponds has resulted in poor survival. Thus, it is costly to pro-        development of domesticated broodstock for the species ap-
                duce large numbers of juvenile lake sturgeon. Paddlefish               pears promising. In 1985-86, a total of 6600 juveniles were
                juveniles have been reared both extensively in ponds and               released in South Carolina waters, of which 541 were 35
                intensively in tanks (Graham et al. 1986). In the extensive            cm in size and were tagged. Preliminary capture data sug-
                approach, ponds are fertilized to induce a dense zooplankton           gest these fish are surviving and growing in the wild, but
                population which serves as food for paddlefish. Ponds are              a number of basic questions need to be addressed. Among
                usually stocked when fry are 5 days old and at a density of            these are questions concerning homing behavior, optimum
                49,400 fish/ha. Average survival is 35 % and growth is rapid.          size of juveniles for release, and size of natural populations.
                At the end of a 140-day growing season, most paddlefish                Studies are underway in South Carolina to examine these and
                are about 250-300 mm in length. In the intensive systems,              other questions which will help determine the feasibility of
                larvae are initially reared on zooplankton (primarily Daphnia)         stock replenishment programs with shormose sturgeon.
                and then trained to accept soft-moist and dry formulated                 There has been interest in stocking programs with the lake
                feeds. Unfortunately, feeding is not efficient because paddle-         sturgeon in several areas of former abundance. The Meno-
                fish do not actively seek feed and they cannot be reared under         minee River, which forms a boundary between the upper
                crowded conditions. Although the intensive approach is suc-            peninsula of Michigan and northeastern Wisconsin, has
                cessful, it requires a large amount of hatchery space.                 several dammed sections that support fishable populations
                                                                                       of lake sturgeon. In 1982, 290 large juveniles (18 cm) and
                                                                                       in 1.983, 11,000 small juveniles (30 nun) were stocked in
                Stock enhancement programs                                             the Sturgeon Falls section of the Menominee River, a site
                                                                                       uninhabited by sturgeons in recent years (Thuen-der 1985).
                Although substantial progress has been achieved in rearing             The area appeared suitable as sturgeon habitat, but subse-
                some of the more important North American sturgeons, ef-               quent sampling efforts and radio telemetry studies indicated
                forts to enhance and/or reestablish fisheries are relatively           that the stocked fish moved out of that section of the river
                small scale. The culture technology for white sturgeon is by           (Dan Folz, Wisc. Dep. Nat. Resourc., Oshkosh, WI, pers.
                far the most developed. There are a number of aquaculture              commun., 18 June 1986). There is speculation that the Lake
                operations in California growing this species as a food fish           Winnebago strain of fish used to stock this area did not
                (Ken Beer, The Fishery, Galt, CA, pers. commun., 2 Oct.                possess the needed behavioral characteristics of the "river
                1986). Further, development of cultured broodstock has pro-            race" of lake sturgeon that inhabit the Menominee River.
                gressed well. At the University of California, Davis, 21/2-3           At present, the Lake Winnebago population of lake sturgeon
                year-old cultured males have been successfully used to fer-            is stable or increasing, and additional spawning sites are being
                tilize eggs from wild-caught females (Serge Doroshov, Univ.            documented in the Wolf River resulting from installation of
                Calif., Davis, CA, pers. commun., 17 June 1986). Further,              additional riprapping of the shoreline accompanying in-
                5-year-old females are beginning to show signs of matura-              creased development. Thus, Wisconsin's main focus is to
                tion. Commercial sturgeon farmers in California now                    refine culture techniques in anticipation of future need
                routinely use cultured males and are rearing females in hopes          (AveLallemant et al. 1983) and to continue to intensively
                of eliminating their dependency on wild fish. In spite of this         manage the existing population in Lake Winnebago to main-
                well-developed hatchery technology, there currently are no             tain a sustained yield (Folz and Meyers 1985). However,
                plans for stocks enhancement programs for white sturgeon,              there are 4-6 locations in Wisconsin formerly containing
                because fishery managers feel that most stocks are stable or           sturgeon populations that appear to be environmentally suited
                increasing. However, the sturgeon fanners are required by              for restocking. Proposed restocking protocol suggest that 3
                their collecting permits to restock sevral thousand sac-fry            years of consecutive stocking should be undertaken using fry,
                per wild sturgeon used for spawning purposes.                          fingerlings, and adults from the same river systems, if possi-
                  On the Atlantic coast, there is substantial interest in estab-       ble, to preserve the genetic integrity of the stocks.
                lishing stocking programs for the Atlantic and shormose                  In Missouri, initial efforts are underway to implement a
                sturgeons. However, difficulties in capture of Atlantic stur-          lake sturgeon reintroduction plan (Graham 1984). Lake
                geon broodstock has thus far prevented initiaion of any                sturgeon were once abundant in Missouri, but now there are

                                                                                  24







              only isolated reports of occasional individuals being caught                    Conclusions
              in the Missouri and Mississippi rivers. Graham (1984)
              evaluated the characteristics of the various state waters and                   Significant progress has been achieved in recent years in
              has identified numerous rivers, lakes, and reservoirs that ap-                  propagating various North American sturgeons. In some
              pear suitable for restocking of lake sturgeon. To test the                      cases, culture technology is sufficiently advanced to provide
              feasibility of the restocking plan, Mark Twain Lake in north-                   the basis for development of an aquaculture industry (e.g.,
              eastern Missouri was stocked in 1984 with 11,800 culture                        white sturgeon; Marx 1986). However, for the most part,
              fingerlings originating from Lake Winnebago sturgeon                            stock enhancement or reintroduction programs are still in
              (Graham 1986a). This new reservoir was selected because                         the conceptual or preliminary stocking-assessment phase for
              it contained abundant natural food, few predators, and tur-                     most species. In many instances, availability of suitable quan-
              bid water. Additionally, a main tributary appeared to offer                     tities of stockable juveniles is the problem, while in other
              suitable spawning conditions. No sampling of the 7900-ha                        cases the sturgeon resources have been so depleted that state
              reservoir has been attempted, but one fish was reported cap-                    management agencies have prior commitments to maintain
              tured in early summer 1986. During the fall 1986, an addi-                      existing fisheries and, therefore, are unwilling to commit the
              tional 10,750 fingerlings (-200 mm in size) were stocked                        resources needed to develop stock enhancement programs.
              into this reservoir to complete the stocking program. Rein-                     Sturgeon populations cross many state boundaries and his-
              troduction success will be evaluated over time, and, depend-                    torically they covered broad expanses of North America.
              ing on the results of this stocking program, other waters in                    Thus, it is proposed that cooperative state-federal programs
              Missouri may be similarly stocked. The feasibility of restock-                  be jointly sponsored, perhaps through regional agreements.
              ing lake sturgeon in selected waters in Minnesota is also                       To a certain degree, the present progress achieved in culture
              under examination.                                                              of North American sturgeons (e.g., white, shormose, lake)
                Several midwestern states have considered stocking paddle-                    is in part attributable to support from various federal agen-
              fish, but lack of a dependable supply of fingerlings has                        cies (e.g., U.S. Fish and Wildlife Service, Sea Grant Office
              delayed stocking efforts. However, from 1970 to 1977,                           of the Department of Commerce). Since sturgeon mature and
              paddlefish were stocked in Table Rock Lake, a 17,500-ha                         spawn at an advanced age, a long-term commitment by the
              lake in southwestern Missouri previously uninhabited by this                    various states and federal agencies will be required to prop-
              species (Graham 1986b). Paddlefish fry (6-8 mm) were                            erly evaluate the potential for stugeon restoration efforts. Un-
              stocked in 1970, but population analyses suggest that these                     fortunately, such commitment does not appear likely from
              fish did not survive. Between 1972 and 1977, 82,600                             any governmental entity at present. For the foreseeable
              (250-300 mm) fingerlings were stocked and these fish                            future, stock enhancement programs will continue on a
              appeared to have an excellent survival rate. Growth of the                      modest scale. Planning and recommendations for stocking
              introduced fish has been rapid and there was evidence of                        programs and their evaluation as proposed by the states of
              spawning in 1983. As a result of this stocking program, an                      Missouri and Wisconsin are commendable and should serve
              expanding sport fishery (by snagging) has developed, with                       as an example to other states and agencies. With proper
              2970 fish caught during 1983-84. In 1984, the estimated                         foresight, the programs underway today could well result
              fishery landings were 18,000 kg, the most successful paddle-                    in a higher level of interest and activity by fishery managers
              fish stocking program to date. Missouri is stocking finger-                     in the future.
              lings in Lake of the Ozarks to maintain a fishery and also
              into Harry S. Truman Reservoir in an attempt to establish
              a population. In 1983, Alabama stocked a 104-ha lake with                       Citations
              440 fish (0.5 kg in size) in the hopes of eventually harvest-
              ing these fish for food. Additionally, the Kansas Game and                      Anderson, E.R.
              Fish Commission stocked about 5000 paddlefish juveniles                              1984 Artificial propagation of lake sturgeon Acipenserfulvescens
              (10-50 cm) into the 3600-ha John Redmon Reservoir in an                                (Rafinesque) under hatchery conditions in Michigan. Mich. Dep.
              attempt to establish a population (Graham 1986b). Besides                              Nat. Resourc., Fish. Res. Rep. 1898, 32 p.
                                                                                              Atz, J.W., and G. Pickford
              the interest to establish fisheries through stocking programs,                       1959 The use of pituitary hormones in fish culture. Endeavour (Engi.
              there is also interest in culturing paddlefish as an aquaculture                       ed.) 18:127.
              species (Semmens and Shelton 1986). However, develop-                           AveLallemant, S., D. Czeskleba, and T. Thuemler
              ment of aquaculture technology for this species is still in the                      1983 Artificial spawning and rearing of the lake sturgeon at the Wild
              preliminary stage.                                                                     Rose State Fish Hatchery, Wisconsin. Wisc. Dep. Nat. Resourc.,
                                                                                                     Fish Culture Note 5, 7 p.
                                                                                              Boschung, H.T., Jr., J.D. Williams, D.W. Gotshall, D.K. Caldwell,
                                                                                                and M.C. Caldwell
                                                                                                   1983 The Audubon Society field guide to North American fishes,
                                                                                                     whales and dolphins. A.A. Knopf Inc., NY, 948 p.
                                                                                              Buckley, J., and B. Kynard
                                                                                                   1981 Spawning and rearing of shortnose sturgeon from the Connec-
                                                                                                     ticut River. Prog. Fish. Cult. 43(2):74-76.


                                                                                         25








                    Cobb, J.N.                                                                          Kohlhorst, D.W.
                         1900 The sturgeon fishery of Delaware River and Bay. Rep. U.S.                      1980 Recent trends in the white sturgeon population in California's
                           Comm. Fish Fish. for 1899, Pt. 25, p. 369-380.                                      Sacramento-San Joaquin estuary. Calif. Fish Game 66(4):210-219.
                    Cochnauer, T.G., J.R. Luckens, and F.E. Partridge                                   Kowtal, G.V., W.H. Clark, Jr., and G.N. Cherr
                         1985 Status of white sturgeon, Acipenser transmontanus, in Idaho.                   .1986 Elimination of the adhesiveness in eggs from the white sturgeon,
                           In Binkowski, F.P., and S.I. Doroshov (eds.), North American                        Acipenser transmontanus: Chemical treatment of fertilized eggs.
                           sturgeons: Biology and aquaculture potential, p. 127-134. Dr W.                     Aquaculture 55(2):139-144.
                           Junk Publ., Netherlands.                                                     Leach, G.C.
                    Czeskleba, D.G., S. AveLallemant, and T.F. Thuemler                                      1920 Artificial propagation of sturgeon, review of sturgeon culture
                         1985 Artificial spawning and rearing of lake sturgeon, Acipenser                      in the United States. Rep. U.S. Fish. Comm. 1919:3-5.
                           fulvescens, in Wild Rose State Fish Hatchery, Wisconsin, 1982-1983.          Leland, J.G. HI
                           Environ. Biol. fish. 14(l):79-86.                                                 1968 A survey of the sturgeon fishery of South Carolina. Contrib.
                    Dadswell, M.J.                                                                             Bears Bluff Lab. 47:1-27.
                         1979 Biology and population characteristics of the shormose sturgeon,          Magnin, E.
                           Acipenser brevirostrum LeSuer 1818 (Osteichthyes: Acipenseridae),                 1964 Croissance en longeur de trois esturgeons d'Amerique du Nord:
                           in the Saint John River Estuary, New Brunswick, Canada. Can. J.                     Acipenser oxythynchus Mitchill, Acipenserfulvescens Raffiensque,
                           Zool. 57:2186-2210.                                                                 et Acipenser brevirostris LeSueur. Int. Ver. Theor. Angew. Limirol.
                    Dean, D.                                                                                   Verb. 15:968-974.
                         1894 Recent experiments in sturgeon hatching on the Delaware River.            Manea, G.
                           U.S. Fish Conun. Bull. (1893) 13:335-339.                                         1%9 Methods for artificial spawning of sturgeons (Acipenseridae) and
                    Doroshov, S.I., and F.P. Binkowski                                                         hatching of fry. Riv. Ital. Piscicoltura ittiopatologia 4(4):81-86.
                         1985 Epilogue: A perspective on sturgeon culture. In Binkowski, F.P.,          Marx, W.
                           and S.I. Doroshov (eds.), North American sturgeons: Biology and                   1986 Life at the bottom makes the sturgeon a tough customer. Smith-
                           aquaculture potential, p. 147-15 1. Dr W. Junk Publ., Netherlands.                  sonian 17(5):82-93.
                    Doroshov, S.I., W.H. Clark, Jr., P.B. Lutes, R.L. Swallow, K.E. Beer,               Meehan, W.E.
                      A.B. McGuire, and M.D. Cochran                                                         1909 Experiments in sturgeon culture. Trans. Am. Fish. Soc. 39:
                         1983 Artificial propagation of the white sturgeon, Acipenser transrnon-               85-91.
                           tanus Richardson. Aquaculture 32:93-104.                                     Miller, R.R.
                    Folz, D.J., and L.S. Meyers                                                              1972 Threatened freshwater fishes of the United States. Trans. Am.
                         1985 Management of the lake sturgeon, Acipenserfulvescens, popula-                    Fish. Soc. 101:239-252.
                           tio'n in the Lake Winnebago system, Wisconsin. In Binkowski, F. P. 9         Murawski, S.A., and A.L. Pacheco
                           and S.I. Doroshov (eds.), North American sturgeons: Biology and                   1977 Biological and fisheries data on Atlantic sturgeon, Acipenser ox)@
                           aquaculture potential, p. 135-146. Dr W. Junk Publ., Netherlands.                   rhynchus. Tech. Ser. Rep. 10, Sandy Hook Lab., Natl. Mar. Fish.
                    Fo1z, D.J., D.G. Czeskleba, and T.F. Thuemler                                              Serv., NOAA, Highlands, NJ, 69 p.
                         1983 Artificial spawning of lake sturgeon in Wisconsin. Prog. Fish-            Pasch, R.W., and C.M. Alexander
                           Cult. 45(4):231-233.                                                              1986 Effects of commercial fishing on paddlefish populations. In
                    Galbreath, J.L.                                                                            Dillard, J., et a]. (eds.), The paddlefish: Status, management and
                         1979 Columbia River colossus - the white sturgeon. Oregon Wildl.                      propagation, p. 46-53. North Central Div., Am. Fish. Soc., Spec.
                           34:3-8@                                                                             Publ. 7.
                         1985 Status, life history, and management of Columbia River white              Priegel, G.R., and T.L. Wirth
                           sturgeon, Acipenser transmontanus. In Binkowski, F.P., and S.I.                   1977 The lake sturgeon: Its life history, ecology and management.
                           Doroshov (eds.), North American sturgeons: Biology and aquaculture                  Wisc. Dep. Nat. Resourc., Publ. 4-3600(77), 20 p.
                           potential, p. 119-126. Dr W. Junk Publ., Netherlands.                        Russell, T.R.
                    Gengerke, T.W.                                                                           1986 Biology and life history of the paddlefish - A review. In Dillard,
                         1986 Distribution and abundance of paddlefish in the United States.                   J., et a]. (eds.), The paddlefish: Status, management and propaga-
                           In Dillard, J., et al. (eds.), The paddlefish: Status, management and               tion, p. 2-21. North Central Div., Am, Fish. Soc., Spec. Publ. 7.
                           propagation, p. 22-35. North Central Div., Am. Fish. Soc., Spec.             Ryder, J.A.
                           Publ. 7.                                                                          1890 The sturgeon and sturgeon industries of the eastern coast of the
                    Graham, K.                                                                                 United States, with an account of experiments bearing upon sturgeon
                         1984 Missouri's lake sturgeon reintroduction plan. Missouri Dep.                      culture. U.S. Fish Comm., Bull. (1888)8:231-238.
                           Conserv., Columbia, MO, 11 p.                                                Seirtmens, K.S., and W.L. Shelton
                    Graham, L.K.                                                                             1986 Opportunities in paddlefish aquaculture. In Dillard, J., et al.
                         1986a Reintroduction of lake sturgeon into Missouri. Final Rep.,                      (eds.), The paddlefish: Status, management and propagation, p. 106-
                           D.J. Proj. F-I-R-35, Study S-35. Missouri Dep. Conserv., Colum-                     113. North Central Div., Am. Fish. Soc., Spec. Publ. 7.
                           bia, MO, 11 p.                                                               Scott, W.B., and E.J. Crossman
                         1986b Establishing and maintining paddlefish populations by stock-                  1973 Freshwater fishes of Canada. Fish. Res. Board Can., Bull. 184,
                           ing. In Dillard, J., et al. (eds.). The paddlefish: Status, management              966 p.
                           and propagation, p. 95-105. North Central Div., Am. Fish. Soc.,              Smith, T.Q.
                           Spec. Publ. 7.                                                                    1985 The fishery, biology, and management of Atlantic sturgeon,
                    Graham, L.K., E.J. Hamilton, T.R. Russell, and C.E. Hicks                                  Acipenser oxyrhynchus, in North America. Environ. Biol. Fish
                         1986 The culture of paddlefish - a review of methods. In Dillard, J.,                 14(l):61-75.
                           et al. (eds.), The paddlefish: Status, management and propagation,           Smith, T.I.J., and E.K. Dingley
                           p. 78-94. North Central Div., Am. Fish. Soc., Spec. Publ. 7.                      1984 Review of biology and culture of Atlantic (Acipenser oxyrhyn-
                    Harkness, W.J.K., and J.R. Dymond                                                          chus) and shormose sturgeon (A. brevirostrum). J. World Maricult.
                         1%1 The lake sturgeon, the history of its fishery and problems of                     Soc. 15:210-218.
                           conservation. Ontario Dep. Lands Forests, Toronto, 121 p.




                                                                                                   26








             Smith, T.I.J., E.K. Dingley, and D.E. Marchette
                  1980 Induced spawning and culture of Atlantic sturgeon. Prog. Fish.
                    Cult. 42:147-151.
                  1981 Culture trials with Atlantic sturgeon, Acipenser oxyrhynchus in
                    the U.S.A. J. World Maricult. Soc. 12:78-87.
             Smith, T.I.J., D.E. Marchette, and R.A. Smiley
                  1982 Life history, ecology, culture and management of Atlantic
                    sturgeon. Acipenser oxyrhynchus oxyrhynchus Mitchill, in South
                    Carolina. S.C. Wildl. Mar. Resour. Res. Dep., Final Rep. to U.S.
                    Fish Wildl. Serv., Proj. AFS-9, 75 p.
             Smith, T.I.J., D.E. Marchette, and G.F. Urich
                  1984 The Atlantic sturgeon fishery in South Carolina. N. Am. J.
                    Fish. Manage. 4:164-176.
             Smith, T.I.J., E.K. Dingley, R.D. Lindsey, S.B. Vansant, R.A. Smiley,
               A.D. Stokes
                  1985 Spawning and culture of shortnose sturgeon, Acipenser brevi-
                    rostrum. J. World Maricult. Soc. 16:104-113.
             Smith, T.I.J., W.E. Jenkins, W.D. Oldland, and R.D. Hamilton
                  1986 Development of nursery systems for shortnose sturgeon, Aci-
                    penser brevirostrum. Proc. Annu. Conf. Southeast. Assoc. Fish
                    Wildl. Agencies 40:169-177.
             Stone, L.
                  1900 The spawning habits of the lake sturgeon (Acipenser rubincun-
                    dus). Trans. Am. Fish. Soc. 29:118-128.
             Taubert, B.D.
                  1980 Reproduction of shortnose sturgeon (Acipenser brevirostrum)
                    in the Holyoke Pool of the Connecticut River, Massachusetts. Copeia
                    1980:114-117.
             Thuemler, T.F.
                  1985 The lake sturgeon, Acipenser Mvescens, in the Menominee
                    River, Wisconsin - Michigan. In Binkowski, F.P., and S.I. Doroshov
                    (eds.), North American sturgeons: Biology and aquaculture poten-
                    tial, p. 73-78. Dr W. Junk Publ., Netherlands.
             Tower, W.S.
                  1909 The passing of the sturgeon: A case of the unparalleled exter-
                    mination of a species. Pop. Sci. Mo. 73:361-371.






































                                                                                         27






           Application of                                                          The release of hatchery-reared juveniles to enhance fisheries
                0                                                                  for a number of species is practiced in Japan and to a lesser
           Yield-per-Recruit and                                                   degree in other countries, including the United States and
                                                                                   Norway (Yatsuyanagi 1982, Botsford and Hobbs 1984,
           Surplus Production Models                                               Isibasi 1984, Ulltang 1984). When juveniles are released to
                                           nhaneeMent                              augment a natural stock that is the basis of an existing fishery,
           to Fishery E                                                            stocking combines extensive mariculture with traditional
                                                                                   fishery science. New quantitative tools are needed to evaluate
           Through Juvenile Releases                                               and manage this system. The simple stocking vs. harvesting
                                                                                   ratios that are used to evaluate and manage aquaculture no
                                                                                   longer apply in the presence of varying fishing pressure and
                                                                                   a natural stock. For example, fishing mortality often increases
           JEFFP,EY I POLOVINA                                                     as stocking levels increase, making it difficult to attribute
           Honolulu Laboratory                                                     any increase in yield solely to the increase in stocking. How-
           Southwest Fisheries Center                                              ever, traditional fishery production models are also inade-
           National Marine Fisheries Service, NOAA                                 quate since they do not incorporate stocking as a variable.
           Honolulu, Hawaii 96822-2396                                             Although some models have been developed to examine the
                                                                                   effects of stocking relative to hatchery cost and the return
                                                                                   to the fishery, these analyses have not taken into account
                                                                                   other management variables including size limits and fishing
           ABSTRACT                                                                effort (e.g., Oshima 1984). More sophisticated models have
                                                                                   been developed which can be used to simulate the effects
           Yield-per-recruit and surplus production models are modified            of stocking or develop optimal fishery policy, and can be
           for use when hatchery-reared juveniles are released into a              applied in situations where the biology of the resource is well
           fishery. The yield-per-recruit model indicates that species with        known and estimates of age-specific population parameters
           low ratios of natural mortality to growth and high asymptotic           are available (Watanabe et al. 1982, Botsford and Hobbs
           weight offer the greatest potential weight yield per stocked
           juvenile. The Ricker surplus production model is easily modi-           1984, Ulltang 1984, Watanabe 1985).
           red to express catches as functions of fishing effort and numbers         In this paper the traditional Beverton and Holt (1957) yield-
           of juveniles released. Thus the model can be used to estimate           per-recruit model and the nonequilibriurn Ricker surplus pro-
           the effectiveness of stocking a fishery with hatchery releases          duction model (Ludwig and Walters 1985), both standard
           based on a time series of catch, stocking, and effort data. The         tools for fishery management, will be modified so that they
           model can also be used as a simulation tool.                            can be applied to evaluate and manage fisheries in which
                                                                                   juveniles are released. The yield-per-recruit model can be
                                                                                   applied with very little modification to juvenile releases to
                                                                                   evaluate the yield-per-released-juvenile as a function of the
                                                                                   biological parameters (growth and mortality) and manage-
                                                                                   ment parameters (release size, size at entry, and fishing mor-
                                                                                   tality). The contribution of the released juveniles to the
                                                                                   spawning stock can be evaluated in a similar fashion by com-
                                                                                   puting the spawning-stock biomass per released juvenile. The
                                                                                   Ricker surplus production model can be modified to express
                                                                                   the catch as a ftinction of effort and stocking so that a time-
                                                                                   series of stocking, catch, and effort data can be analyzed to
                                                                                   evaluate the effectiveness of stocking and to estimate max-
                                                                                   imum sustainable yield in the presence of juvenile releases.


                                                                                   Yield-per-recruit models

                                                                                   The Beverton and Holt (1957) yield equation can be for-
                                                                                   mulated as a function of the ratio of instantaneous mortality
                                                                                   to von Bertalanffy growth (MIK), the ratio of length at
                                                                                   recruitment to the fishery to asymptotic length (c), the ratio
                                                                                   of fishing mortality to natural mortality (FIM), and the ratio
                                                                                   of length of the stocked juvenile to the asymptotic length (a).

                                                                              29











                                                                                                    0.20
                            ZJa                                                                     0.25                    1.0-.                             0.5
                            >1                                                                   -0.30                    8

                                                                                                                                                                                           0.3
                                                                                                    0.40
                            LL

                                                                                                    0.40                                                                                   0.15
                                                                                                    0.30

                                                                                                    0.25
                                                                                                                                                                                           .05
                                                                                                    0.20                LLJ  .4-
                            -C


                                                                                                                             .2-
                                 0      0!5      1      lt      2!0     2!5     A       A      4@
                                             Fishing Mortality/ Natural Mortality                                                      '5      1                                         3!5     4!0
                                                                                                                                0     0.       .0      15      A        2.5     3'0
                                                                                                                                            Fishing Mortality/ Natural Mortality
                                                           Figure 1
                        Yield per stocked juvenile for Pristipomoides fflamentosus as function                                                          Figure 2
                        of relative length of entry and relative fishing mortality. Estimates of                    Spawning-stock biomass (kg) per stocked juvenile for Ptislipomoides
                        MIK = 1.7, W. = 8.5 kg taken from Ralston (1981); size of release                           ftlamentosus as function of relative length of entry and relative fishing
                                                       taken as 0.1 L..                                             mortality. Estimates of MIK = 1.7, W@ = 8.5 kg taken from Ralston
                                                                                                                    (1981); size of onset of sexual maturity taken as 0.5 k; size of release
                                                                                                                                                      set at 0.1 L_.
                        Under this formulation the yield (Y) per stocked juveniles
                        (S) is:
                                                                                                                    population spawning-stock biomass to a given level. The
                        Y/S                                                                                         SSBIS and YIS equations, together with the hatchery costs
                        (MIK) (FIM) ((I - c)l(l - a))(MIK)(11 (MIK + (FIM) (MIK))                                   and the value of the harvested fish, can serve to evaluate the
                                                                                                                    economic benefits of the release programs as functions of
                        - 3 (1 - c)l(l + (MIK) + (FIM) (MIK))                                                       variables c, a, MIK, and FIM.
                        +3(l     - C)2/(2 + WK) + (MIK) (FIM))                                                         Hatchery technology and knowledge of the early-life
                                                                                                                    history of marine organisms have made it possible to rear
                            (1 - C)31(3 + (MIK) + (FIM) (MIK)).                                                     numerous marine organisms. The YIS and SSBIS equations
                                                                                                                    permit comparisons of the benefits from stocking among
                        In a similar fashion, the spawning-stock biomass can be ex-                                 species with different population parameters. For example,
                        pressed as a function of the same variables plus the ratio of                               there are three commercially important species in Hawaii that
                        the length at onset of sexual maturity to the asymptotic length                             might be candidates for hatchery release programs: Mahi-
                        (Beddington and Cooke 1983).                                                                mahi, Coryphaena hippurus; a snapper, P. filamentosus; and
                          Based on these formulations, just as in the traditional yield-                            a spiny lobster, Panuhrus nwrginatus. The YIS isopledis were
                        per-recruit analysis, the yield-per-stocked juvenile (YIS) and                              computed for each of these species, and the maximum values
                        the contribution of the stocked juvenile to the spawning stock                              of' YIS, for all c, as a function of FIM, were determined.
                        biomass (SSBIS) can be calculated as functions of FIM and                                   These maximum values of YIS are plotted for the three
                        c (Figs. 1,2). The value of the yield per stocked juvenile                                  species (Fig. 3). The differences between the three species
                        varies considerably with c and FIM, so the proper choice                                    in their contribution to the fishery are striking. For exam-
                        of FIM and c is necessary to maximize the benefit from stock-                               ple, when fishing mortality is equal to natural mortality and
                        ing. For example, in Figure 1, when the length of entry to                                  the size at entry to the fishery is optimal, a released spiny
                        the fishery is 50% of the asymptotic length, a hatchery-                                    lobster will contribute 0.02 kg to the fishery, a released snap-
                        released juvenile opakapaka, Pristiponioides filamentosus,                                  per will contribute 0.3 kg, and a released mahimahi will con-
                        contributes 0.3 kg to the fishery when fishing mortality equals                             tribute an amazing 2.5 kg. Even when price per kilogram
                        natural mortality; whereas when fishing mortality increases                                 is considered and the possibility that only 25-50% of adult
                        to 1.5 natural mortality, at the same size of entry, the con-                               mahimahi remain around the islands, the mahimahi releases
                        tribution to the fishery of a hatchery-released juvenile opa-                               appear to offer high economic return. The contribution of
                        kapaka will increase 33% to 0.4 kg. The SSBIS isopleths                                     a released mahimahi to the fishery is so much greater than
                        indicate the contribution of a stocked juvenile to the popula-                              that of the snapper, and in turn the contribution of a snapper
                        tion spawning-stock biomass. For example, for the snapper                                   is greater than that of the spiny lobster, largely because of
                        (opakapaka) when FIM = 1.5 and c = 0.5, a stockedjuvenile                                   differences in the MIK ratio (1.0 for mahimahi, 1.7 for snap-
                        will contribute 0. 15 kg to the population spawning-stock                                   per, and 3.0 for lobster) and the asymptotic weight (30 kg
                        biomass (Fig. 2). If the spawning-stock biomass of the                                      for mahimahi, 8.5 kg for snapper, and 1.7 kg for spiny
                        population is known, the SSBIS equation can estimate the                                    lobster). The lower the ratio of natural mortality to growth,
                        number of juveniles needed to be released to increase the                                   the greater the survival of the released individual; and the

                                                                                                              30







                                                                                                   To modify these equations to include H, hatchery-released
                    3.0--                                                    Mahimahl           juveniles in year t before harvesting, it is necessary to express
                                                                                                the biomass in year t + I resulting from H, A power func-
                  .2 2.5--                                                                      tion relationship
                  C
                  :3                                                                                                                    (Ht)b
                                                                                                                             Bt+1 =a
                    2.0--
                  (D
                  0                                                                             with parameters a and b appears appropriate for hatchery
                                                                                                releases of Oregon coho salmon (Peterman and Routledge
                  CL                                                                            1983). For a fast-growing species the major contribution
                  -a 1.0- -
                  :-:5                                                                          from stocking to the fishable biomass will occur in the same
                  -0                                                                            year as the stocking, and thus H,+ 1 rather than H, would be
                  A?
                                                                     Opakapaka                  used in the power function equation.
                                                                    Spiny Lobster                  If the biomass from the hatchery-released stock is simply
                             0Z      is      1.5    A      2!5    3.0     3.5     4'0           added to that of the natural stock in the first equation of the
                                   Fishing Mortality/ Natural Mortality                         Ricker model for surplus production, then we obtain:
                                             Figure 3                                                      B,+1 = S, exp(A - BSt + Ut) + a(Ht)b.                        (4)
             Maximum yield per stocked juvenile as a function of relative fishing
             mortality for mahimabi, opakapaka, and spiny lobster. Parameter esti-              This modified equation, together with the two other equa-
             mates for mahimahi MIK = 1.0, W = 30 kg (Uchiyama et al. 1986); for                tions of the Ricker model, produces a production model
             opakapaka MIK = 1.7, W = 8.5 kg (Ralston 1981); for spiny lobster                  which incorporates hatchery releases. The contribution of
                         MIK = 3.0, W = 1.7 kg (Polovina unpubl. data).                         the hatchery releases will increase the catch directly through
                                                                                                Equation (3) and those that are not caught will increase S,
                                                                                                through Equation (2).
             greater the asymptotic weight, the greater the weight gained                          The Ricker surplus model without stocking shows the usual
             by the released individual. The SSBIS follows the same order                       dome shape in which production first increases then decreases
             for the three species as YIS. Thus among the candidates for                        ultimately to zero with increasing fishing mortality (Fig. 4).
             juvenile release, those with low MIK ratios and high asymp-                        When a fixed number of hatchery releases are added to the
             totic weights will offer the greatest contribution in biomass                      system, the yield curve has the usual dome shape as a func-
             to the fishery.                                                                    tion of fishing mortality; but rather than declining to zero,
                                                                                                as is the case of an unstocked population, the yield approaches
                                                                                                an asymptotic yield of a(Ht)b          with increasing fishing mor-
             Fishery production models                                                          tality (Fig. 4). The relative contribution of the releases to
                                                                                                the fishery will be greatest for relatively high levels of fishing
             with stocking                                                                      mortality. Hatchery releases can increase the maximum yield
             The most frequently used production models, Schaefer and                           and the corresponding level of optimum fishing effort.
             Gulland-Fox, do not explicitly specify a recruitment relation-                        If hatchery releases occur in the absence of a natural
             ship, and hence do not easily lend themselves to modifica-                         population the Ricker model with stocking just reduces one
             tion to include hatchery releases. However, the Ricker model                       equation:
             for surplus production (Ludwig and Hilborn 1983) is a sim-                                           C, = a (H,)b    (1 - exp (- qE,)).
             ple production model which can easily handle stocking. The
             Ricker model for surplus production is expressed by the                               Unfortunately, due to the nonlinear nature of the Ricker
             following three equations (Ludwig and Walters 1985):                               surplus production model, it is not as easy to estimate the
                                                                                                parameters as, for example, for the Schaefer model. A com-
                               B,+      S, exp (A - BS, + UI)                        (1)        plete approach to parameter estimation for the Ricker model
                                                                                                is presented in Ludwig and Hilborn (1983). Here a simplified
                                   S, = B, - C,                                      (2)        approach will be presented for the Ricker model with stock-
                                                                                                ing when it is assumed that the fishing effort is measured
                                  C, = B, (I - exp (- qE,))                          (3)        without error. First, assume a value for q and compute B,
                                                                                                and C, from Equations (2) and (3). Then estimate A, B, a,
             where B, is the population biomass in year t, S, is                     the        and b from Equation (4) with the nonlinear regression, using
             biomass remaining after harvest in year t, C, represents the                       the B's and S's obtained from the previous step. Finally,
             catch in year t, E, denotes the effort in year t, U, represents                    vary q and repeat the previous steps until the sums of squares
             independent normally distributed random variables with mean                        of the nonlinear regression are minimized. Computer pro-
             0 and variance v, and A, B, and q are parameters estimated                         grams for nonlinear regression can typically be used as a basis
             from catch and effort data.                                                        for this parameter estimation approach.

                                                                                          31











                                                             60--




                                                             50--


                                                                                                                         With Stacking
                                                             40--


                                                        0

                                                             30--

                                                                                                    Without Stocking
                                                       C)
                                                             20--




                                                             10
                                                             00 11 02 0 3 0 4 0  5 0.6 0.7 0.8 o.9     1   u   @21 3 1 @41      1 @61 I I @11
                                                                                 Fishing Mortality / Natural Mortality


                                                                                                 Figure 4
                                                    Equilibrium Ricker surplus production model with and without stocking. Curve without stock-
                                                    ing based on biomass model B = S exp (0.7 - 0.007S); curve with stocking based on B                  S
                                                                                           exp (0.7 - 007S) + 25.




                        An experimental approach to stocking can be an efficient
                     means of evaluating the effectiveness of stocking and identify-                              57--
                     ing optimal stocking levels, but simulation of any design is                                 56--
                     a necessary first step before implementation. For example,                                   55--
                     releasing juveniles into a fishery on alternating years and then
                     comparing catches in years with stocking to catches in years                                 54--
                     without stocking may be considered a way to estimate the                                     53--
                     effectiveness of stocking. This experimental design can be
                                                                                                                  52--
                     simulated with the stocking surplus production model (Fig.
                     5). Suppose a population has a carrying-capacity biomass of                                  51--
                     100 t and is fished with a fishing mortality of F = 1.0. Sup-                                50--
                     pose juveniles are released in a quantity which contributes
                     20 t to the fishable biomass over a 10-year period on years                                  49                             '5                          9t
                     2, 4, 6, 8, and 10, and no releases occur in years 1, 3, 5,                                                                  Years
                     7, and 9. The stocking surplus production model estimates                             L
                     that equilibrium fishing with F= 1.0 results in a catch of                                                             Figure 5
                     about 49 t annually. The first stocking (year 2) increases the                        Simulation of yield with F= 1.0 when stocking occurs on even num-
                     catch to 62 t, and then the catch follows an oscillating se-                          bered years. Parameters of the Ricker surplus production model with
                     quence of lower catches during years without stocking and                                          stocking are: A     1.2, B    0.007, a (H,)'= 20t.
                     higher catches during years with stocking. The oscillating
                     sequence has an increasing trend over time as the stock bio-
                     mass grows due to stocking. At some point an equilibrium
                     would be reached and the sequence would 6scillate between
                     the same two levels of catch. However, the use of this design
                     to estimate the effectiveness of stocking by comparing catches
                     between years with and without stocking would underestimate                        .1 St.,
                                                                                                    WIt",

























































                     the effectiveness of stocking at this level of fishing mortality,
                     since the catches do not return to their prestocking level
                     between years of stocking.



                                                                                                      32







              Citations


              Beddington, J.R., and J.G. Cooke
                  1983 The potential yield of fish stocks. FAO Fish. Tech. Pap. 242,
                     47 p.
              Beverton, R.J.H., and S.j. Holt
                  1957    On the dynamics of exploited fish populations. Fish. Invest.
                     Ser. II Mar. Fish. G.B. Minist. Agric. Fish. Food 19, 533 p.
              Botsford, L.W., and R.C. Hobbs
                  1984    Optimal fishery policy with artificial enhancement through stock
                     ing: California's white sturgeon as an example. Ecol. Model. 23:
                     293-312.
              Isibasi, K.
                  1984 A statistical assessment on the effect of liberation of larvae in
                     the sea-farming-I. On the effect of liberation in the case of Kuruma
                     prawn (Penaeusjaponicus). Bull. Tokai Reg. Fish. Res. Lab. 113:
                     141-155.
              Ludwig, D., and R. Hilborn
                  1983 Adaptive probing strategies for age-structured fish stocks. Can.
                     J. Fish. Aquat. Sci. 40:559-569.
              Ludwig, D., and C.j. Walters
                  1985 Are age-structured models appropriate for catch-effort data?
                     Can. J. Fish. Aquat. Sci. 42:1066-1072.
              Oshima, Y.
                  1984 Status of fish farming and related technological development in
                     the cultivation of aquatic resources in Japan. InLiao,I.C.,andR.
                     Hirano (eds.), Proceedings of ROC-JAPAN Symposium on Mari-
                     culture,p.1-11. TML Conference Proceedings 1, Tungkang Mar.
                     Lab., Tungkang, Pingturig, Taiwan, R.O.C.
              Peterman, R.M., and R.D. Routledge
                  1983 Experimental management of Oregon coho salmon (Oncorhyn-
                     chtis kisutch): Designing for yield of information. Can. J. Fish.
                     Aquat. Sci. 40:12124223.
              Ralston S.
                  1981 A study of the Hawaiian deepsea handline fishery with special
                     reference to the population dynamics of opakapaka, Pristipomoides
                     filamentosus. Ph.D. Diss., Univ. Wash., Seattle, 204 p.
              Uchlyama, J.H., R.K. Burch, and S.A. Kraul
                  1986 Growth of dolphins, Coryphaena hippurus and C. equiselis, in
                     Hawaiian waters as determined by daily increments on otoliths.
                     Fish. Bull., U.S. 94:186-191.
              Ulltang, 0.
                  1984 The management of cod stocks with special reference to growth
                     and recruitment overfishing and the question whether artificial propa-
                     gation can help to solve management problems. In Dahl, E., et al.
                     (eds.), The propagation of cod Gadus morhua L., p. 795-817.
                     Flodevigen, rapp. 1.
              Watanabe, S.
                  1985 Restocking effects on the two competing species system, in-
                     cluding a nonlinear regulated species population. J. Tokyo Univ.
                     Fish. 72(2):57-63.
              Watanabe, S., R. Matsunaga, and H. Fushimi
                  1982 Age-structured matrix model including catch and restocking.
                     J. Tokyo Univ. Fish. 68(1-2):15-23.
              Yatsuyanagi, K.
                  1982 Productive effect in stocking of prawn seedling in water adja-
                     cent to Yamaguchi Pref. and Suho-Nada. Bull. Yamaguchi Prefect.
                     Naikai Fish. Exp. Stn. 10, 52 p. [in Jpn.].












                                                                                             33






             Some Aspects of                                                            Scallop mariculture in Japan is a new and rapidly evolving
                                                                                        mariculture industry, presently very important in the north-
             Offshore Spat Collection                                                   ern part of Japan (Ito 1988, 1989b). Its development is at-
                                                                                        tributed to the success of mass production of scallop seeds.
             of Japanese ScaRop                                                         The seeds are produced from natural spat collection and in-
                                                                                        termediate culture in the sea. Although seed production first
                                                                                        took place in embayment areas, it is now practiced in shallow
                                                                                        waters of both embayment areas and the open sea. Off open
             HIROSHI ITO                                                                coasts, spat collection is frequently unsuccessful; however,
             Hokkaido Regional Fisheries Research Laboratory                            spat collected offshore have become indispensable to the
             Fisheries Agency of Japan                                                  Japanese scallop culture industry in recent years. Therefore,
             116 Katsurakoi, Kushiro City                                               there is an urgent need to establish efficient methods for off-
             Hokkaido, 085 Japan                                                        shore spat collection. Some research has been done on this
                                                                                        subject and has provided clues to the establishment of such
                                                                                        methods.
                                                                                          In this report, the author will review the biology of Japa-
             ABSTRACT                                                                   nese scallop and trends in scallop production and offshore
             The recent information on offshore spat collection of Japanese             spat collection in Japan, and present results of recent off-
             scallop, Patinopecten (Mizuhopecten) yessoensis JAY, is briefly            shore spat collection in Neniuro Straits, eastern Hokkaido.
             outlined. Scallop mariculture in Japan has developed rapidly
             due to technical advances in the methods for spat collection and
             intermediate culture made in the mid-1960s. The spat collected             Biology of Japanese scallop
             offshore is indispensable to Japanese scallop mariculture that
             has evolved since the mid-1970s. Nevertheless, offshore spat               Japanese scallop (giant yezo scallop), Patinopecten (Mizu-
             collection is frequently unsuccessful because of the intricate fluc-       hopecten) yessoensis JAY, "Hotate-gai" in Japanese, is
             tuations in open sea conditions. Therefore, some research has              classified in the phylum Mollusca, class Bivalvia (Lamelli-
             been perforinqd in recent years on larval monitoring. The results          branchia or Pelecypoda), order Pteriomorphia, and family
             to date have shown that the scallop veliger larvae are distrib-            Pectinidae. This scallop is a cold-water species distributed
             uted at comparatively higher densities in particular waters                in the subfrigid coastal areas of the north Pacific Ocean, the
             (temperature 7-8*C, salinity 32.0-32.5) along the coasts.                  south Okhotsk Sea and the Japan Sea, along the coasts of
                                                                                        the Kuril Islands, Sakhalin, Hokkaido, northern Honshu,
                                                                                        Sikhota Alin, and northern Korea. The southern limit of
                                                                                        the natural distribution in Japan is Toyama Bay on the
                                                                                        Japan Sea coast and Tokyo Bay on the Pacific Ocean coast
                                                                                        (Fig. 1).
                                                                                          The life cycle is as follows (Fig. 2): Demersal eggs fer-
                                                                                        tilized in the sea after spawning. Fertilized eggs begin
                                                                                        cleavage and reach the trochophore state at 4 days. The early
                                                                                        veliger larva with a fully formed prodissoconch shell, called
                                                                                        the D-shaped larva because of the straight hinge shell, is
                                                                                        reached 5-7 days after fertilization. By 30-35 days, the
                                                                                        umbones of the late veliger larva are fully grown and
                                                                                        overhang the straight hinge. The pediveliger attaches to the
                                                                                        substratum with byssal threads 40 days after fertilization. Im-
                                                                                        mediately after attaching, rapid changes in shell morphology
                                                                                        of the dissoconch (spat shell) and growth of internal organs
                                                                                        take place, leading to the adult scallop form (Yamamoto
                                                                                        1964, Marti 1972).
                                                                                          After the attached spat have grown to about I cm shell
                                                                                        length, they start to be released from the substratum and the
                                                                                        spat inhabit the sea bottom. This scallop is gonochoristic in
                                                                                        sexuality (Yamamoto 1943). Rarely, hermaphroditic indivi-
                                                                                        duals are found (Yamamoto 1964, Maru 1978b). Juveniles
                                                                                        are lacking in a well-developed gonad and differentiate sex-
                                                                                        ually at about 15 months. Adults are more than 2 years old

                                                                                   35








                                        1400                                                        145u*E
                                           APAN                                 a            1_@OKHOTSK
                                                              S 0 Y A S T;@R@j

                                                          IEIUN
                                            SEA                                                          SEA
                                    45ON                 RI IRI



                                                         TEURI
                                                         is.
                                                                                       SAROMA     NOMRO
                                                                                        LAKE       LAKE
                                                                 _T


                                                                                           K

                                                                                                                 @UNA
                                                                                                                 H RI S
                                                                              K A     I  D 0                    RO

                                                              ----------                                         N

                                                                                           . . . . . . . . . .

                                                                       0
                                                                          -2f-
                                                                        :::c z   1!:N5


                                  @)HIKI
                                         zF51
                                   IS.

                                                 (PbNKA BAY)

                                               3t,-
                                                                                                                          4@0
                                                                    PAC I F I C
                                  tio             M   U                               17
                                                                        CEAN




                                                                                              -13     1       1

                                                                           Figure 1
                                         Main scallop mariculture areas in Japan and natural distribution in the northern sea.




               (Wakui and Obara 1967; Marti 1976, 1978a; Osanai et al.             mesh size and "netion net" in the larger. The bag filler is
               1980; Kawamata et al. 198 1). The gonads grow from autumn           usually netlon net and waste fishing nets. The spat collected
               to winter and become mature in spring. The eggs and sperm           by these collector bags hung from longlines are then caged
               are released after maturation in the spring.                        for seed production during a period of several months. This
                                                                                   cage culture for seed production is called "intermediate
                                                                                   culture. " The intermediate culture seeds are used for hang-
               Scaflop production in Japan                                         ing culture in exclusively designated sea areas and for sow-
                                                                                   ing culture on prepared sea bottoms.
               Scallop mariculture developed rapidly due to technical              I Scallop production in Japan remained at a low level of
               advances in the successful methods of natural spat collec-          5,ODO-20,000 metric tons for a quarter of a century, until
               tion and intermediate culture in embayments in the mid-             1970. After this, the hanging culture production increased,
               1960s. Scallop spat collection in Japan was first attempted         mainly in embayment areas such as Mutsu Bay in Aomori
               in Saroma Lake in 1934 (Kinoshita 1935). After many ex-             Prefecture, and Funka Bay and Saroma Lake in Hokkaido
               periments, a successful scallop spat collector was invented         (Fig. 3). After 1975, the sowing culture production increased
               in 1964, primarily by Toyosaku Kudo, a fisherman in Mutsu           rapidly, mainly in the coastal regions of Soya and Abashiri
               Bay, Aomori Prefecture (Yamamoto et al. 1971, Tsubata               in north Hokkaido, facing the Okhotsk Sea. In 1982, the pro-
               1982). The scallop collector is composed of a mesh bag filled       duction of hanging culture amounted to 77,000 tons, and the
               with the substratum. The bag is made of a small or large            production from sowing culture and fishing on wild stocks
               synthetic fiber mesh, call "Japanese onion bag" in the small

                                                                              36





Figure 2
Life cycle of the scallop Patinopecten (Mizuhopecten)yessoensis (Jay), with notes on cultuew methods. (Modified
from Yammamota 1964; Maru 1972, 1976, 1978a,b; Kawamata et al. 1981.)



reacged a little short of 100,000 tons, for a total production		10 years (Fig. 4.). Most of the seeds are sown in the coastal
of 176,000 tons.										retions of northern and eastern Hokkaido in this order:
	The scallop takes first place, by value, in molluscan shell-	Abashiri (990 million shells, 66%), Nemuro (200 million
fish production in Japan, with a three-fold increase in pro-		shells, 13%), and Soya (180 million shells, 12%). The seeds
duction and a four-fold increase in value over the last 10			for sowing culture and produced in the Rumoi, Soya, and 
years. The value in 1982 amounted to 42 thousand million			Nemuro regions, and depend mainly on offshore spat col-
yeb, At present, sowing culture and wild production account			lection. These seeds, collected offshore, are mainly used for
for 56% of the total, and sowing culture keeps the scallop			sowing culture. Therefore, offshore spall collection is equally
industry prosperous. The rapid development of sowing				indispensable as collection in embayments for sowing culture.
culture is attributed to the mass production of scallop seeds.
The number of seeds sown around Hokkaido amounted to 
1,500 million shells in 1982, a three-fold increase in the last


37







                         80   HANGING CULTURE                                                      RbMOj
                                                                                              0
                                                       A             TOHOKU                   2    sbYA
                                                                   NOMHEM AREAS
                                                                   OF HONSHtI ISLAND          0
                                                                                                  I
                                                                                              2    NINUAO'
                         50-

                                                OMORI                                         0
                                                                   -IBURI  :-Do          D    10-  ABASH I R I

                                                                       @A
                      100
                                                                                         Z
                                                                   NORTHUtN AREAS
                                                                   OF HCNSHJ  ISLAND

                                                                        A
                                                    OSHIMA
                                                                   :-C
                    0                                                  E`A@              X   15- 5
                          0 Lr'.
                                                                                                                    . .. .... .
                    U)                                                                   X
                    z
                              WILD AND                                                   2
                              SOWING CULTURE                                             :D
                    0
                                                                                             10-0
                                                           ABAWRI
                    F- 50-
                    LLJ                                                HOKKAIDO          'D
                                                                   OKHOTSK
                                                                                                                             ..... . ..........
                                                                    StA                  Z         TOTAL                      'INTRO.DUCTIION
                                                                   COAST
                    z
                    2                                                                    :_u  5-
                    U
                                             TOHOK,I
                                                                                                                                 INDEPENDENT
                    0
                    CL
                        0                        1475, 4    '19,80,                           0
                                                                                                1965         1970         1 d75        1480
                                        Y E A      R                                                            Y E A R

                                           Figure 3
                           Recent trends in Japanese scallop production.                                         Figure 4
                                                                                      Recent trends in yearly seed input for scallop sowing around HokWdo.




                 Offshore spat collection                                             are the important factors related to spawning, and are used
                                                                                      as a precursor to monitor the planktonic larvae. The gonad
                 Offshore spat collection off open coasts has been done com-          index increases rapidly, reaches a maximum value in spring
                 mercially since the mid-1970s (Maru and Nakagawa 1979,               before breeding, and then rapidly decreases to a minimum
                 Shiogaki et al. 1980). The spat collected offshore have ac-          in summer after breeding. Changes in the index are moni-
                 counted for half the seed supply for sowing culture since 1980       tored and the breeding time is estimated. Increases in water
                 (Fig. 5). The offshore areas for spat collection operations          temperature progress in the following order: Japan Sea coast,
                 are distributed along the coasts of the northern Japan Sea,          Okhotsk Sea coast, and the Nemuro Straits coast (Fig. 8).
                 the Okhotsk Sea, Nemuro Straits off Hokkaido, an Tsugaru             Likewise, scallop breeding along the open coasts around
                 Straits and the Pacific Ocean off Aomori Prefecture. Most            Hokkaido generally begins first on the Japan Sea coast,
                 of the offshore spat are collected around Hokkaido.                  second on the Okhotsk Sea coast, and third in the Nemuro
                    Environmental conditions of the open coast during spat col-       Straits (Fig. 9). Local differences in breeding times are well
                 lection fluctuate intricately because of seasonal changes in         explained by differences in water temperatures. Coastal
                 the water masses from spring to summer (Fig. 6,7). The               surfacewater temperatures during the breeding period range
                 Tsushima and Soya warm currents influence the waters                 from 8 to 12'C; however, bottom temperatures are also
                 around Hokkaido to raise the temperature at this time                partially involved. The coastal surfacewater temperature is
                 (Komaki 1975, Fujii and Sato 1977). Spat collection occurs           2-:3'C higher than the bottom temperature. Thus, the scallops
                 in the coastal areas directly influenced by coastal waters, and      probably breed in 5-10'C temperatures, but accurate mea-
                 i
                 ndirectly  influenced by oceanic waters.                             surements have not yet been obtained.
                    The breeding season of scallops along the open coasts
                 around Hokkaido extends from April to July. The scallop
                 is induced to spawn by factors controlled by the animal itself
                 and by environmental conditions. The gonad index (gonad
                 weight X 100/soft body weight) and the water temperature

                                                                                  38





Figure 5
Recent trends in number of scallop seed marketed.

	The scallop larvae are moniored with plankton analysis
for spatfall perdiction. In embayments, the densities of the 
larvae ususlly range from 100 to 10,000 individuals/m3
seawater (Maru 1985). Nevertheless, the offshore larvae are
very few and their densities fall to lower levels, 10% to 1%
of those in embayments (Fig. 10). As a result, industrial
methods for offshore spat collection are at present not
established, and collection is frequently unsuccessful. More-
over, data realted to this are scarce. Therefore, research has
been carried out in offshore areas for spat collecting, and 
following are the results of our research in Nemuro Straits.

Research in Nemuro Straits

Industrial spat collection has been attempted since 1977 in 
Nemuro Straits (Fig. 11), eash Hokkaido, near the southern
Kuriles, although it was unsuccessful during the period
1977-81. In 1982, a research project for this region was
begun by this author and co-workers of a special team
organized to concentrate systematically on creative concepts
of scallop mariculture (Ito 1989a). The research area ex-
tended along 350 km of coastline from the Shiretoko Penin-
sula facing the Okhotsk Sea to the Nemuro Penisula facing
the Pacific Ocean. Water depths investigated range from a 
few to 1000 meters, since the northern region becames rapid-
ly deeper than the southern. THe vertical search range ex-
tended to depths. The biological and environmetal research took
place aboard four vessels at half-week or one-week inter-
vals for 4 months, from April to July.

			Figure 6
Main water currents around Hokkaido, summer and winter.

39














                                                    L:: .........
                                                     ..............
                                                                   m 'm
                                      0                    ......
                                       0
                             ...............
                                K; ....
                                                                                                           OMAN*
                                                                                                           Q@e
                                                                                       ... ......                                 ..


                                     0


                                                      -E

                                                                  SPRING
                                                                                                                       AUTUMN
                                                              F
                                                                                                                      F


                                eK
                                                                                      Me




                                         w      A


                                ...........
                              ..............













                                                                                               ........... ...
                            ....                                SUMMEk                                                  WINTER

                                                                                                                      F

                                                 I ...... .ell




                      JAPAN               WATER TEMPERATURE                      0C
                       SEA IMASHIKE -           2          4     6      10 12 14 16 182022               20 1816 14 12 10 8 6
                      COASTI    PAE -
                            @TtOA TB0



                                               41
                            IESASHI
                 -J OKHOTSKIOOMU
                 <     SEA IMONBETSU-
                 (_)  COAST I
                 0          1
                 -j         I

                            UTORO
                            @RAIJSU


                     NEMUROINEMURO
                       STR.            2 0              0                                                                     4
                      COAST
                                       JAN.     FEB. MAR. APR. 1 @@AY. 1UN7JUL.'AUG.l SEP.'OCT. 1 NOV DEC.

                                                           T I ME OF YEAR                    1982


                                                                          40







           Figure 7
           Seasonal water masses around Hokkaido. A, Tsushima warm current;
           B, Tsugaru warm current; C, Soya warm current; D, northward cur-
           rent of the Kuroshio; E, coastal branch off the Oyashio (Kuril cold cur-
           rent); F, offshore branch off the Oyashio (Kura cold current); G, east
           Sakhalin cold current; H, Liman cold current; I, west Sakhalin coastal
           water; J, cold water west off Tsugaru Straits; K, cold water west off
           Musashi-tai; L, inter-cool water; M, mixed water area of circulating
           current; N, floating ice area; 0, coastal water area. (After Komaki 1975,
           Fujii and Sato 1977.)


           Figure 8
           Surface temperature changes of coastal waters relative to locality around
           Hokkaido, 1982.





                                                                 Ai
                                  00                             JAPAN
                                0     41 0                       SEA

                                                                 COAST
                                                                 IF
                                                                                                                                      ___jU
                  SARUFUTSU
                                     o                                                                      YELIGER N-


                                                                                                                                      Ao




                  00MU
                                                                                                                   o' 1-11



                                                                 OKHOTSK

                                                                 SEA

                  SARURU
                                                                 COAST







                  mONBETSU
                                                                                                      I L

                                                                 AL
                  RAUSU


                                                    U U u
                                                                                           MAY             JUN.            JUL.


                x SHIBETSU                                       NEMURO                                   Figure 10
                z                                                                Changes in numbers of scallop veligers and attached spats on the coasts
                D                                                STRAITS              of Okhotsk Sea and Nemuro Straits off Hokkaido, 1982.
                <
                z
                0                                                COAST
                o

                40
                30, NOTSUKE
                20@

                10
                0                                                V
                    MAR.        APR.       MAY        JUN.       JUL.


                                      Figure 9
           Changes in gonad index (gonad weight x 100/soft body weight) of adult
                   scallop relative to locality around Hokkaido, 1982.

                                                                            41










                                                            14VE                                                   N
                                                                                                      5      lon,m,+
                                                      0 K H 0 T S K     S E A      ._"en      0







                                                        0
                                                                    0"     '17.:
                                                                   s'
                                                                 N

                                                                                                                            44'N











                                                                          20

                                                                                             5T
                                                                                                                          20'_'\@
                                                                      NOTSU-
                                                                      KE PE
                                                                        ODAITO*


                                                           OKHOTSK SEA                       C
                                                                                             ri
                                                                                             C@_
                                                JAPAN SEA
                                                                                                 --@B A Y
                                                                                         EMURO

                                                                               K e
                                                        H0 K K A

                                                                                                     *
                                                                                                        MURO,
                                                                                                      NE


                                                                                                                    CID
                                                                           LAGOON HOREN K

                                                                                                      00
                                                        PACIFIC OCEAN
                                                                                                          ACIFIC      OCEAN
                                                 O'N S H'U



                                                                                 Figure 11
                                                                         Location of Nemuro :Straits.





                   In Nernuro Straits, the spawning period varied with the                   The distribution of planktonic larvae shows fast-moving
                 location of the scallop habitat. For 1982 it was estimated to            kaleidoscopic changes, with time (Figs. 15, 16). Environ-
                 be (Fig. 12) early-June to early-July at Rausu (northern                 mental conditions of the open coast also fluctuate intricately
                 region), mid-June at Shibetsu (middle region), and late-May              and are not easily forecast. However, it appears possible to
                 at Bekkai (southern region). In short, the scallop spawned               draw conclusions from the phenomena observed. The lar-
                 earlier in souther than in northern areas. This is well ex-              val distribution is not regulated simply by temperature and
                 plained by the time lag in temperature increase. Bottom                  salinity, but seems to have some relation to water masses
                 temperatures at spawning are similar at different localities,            in the coastal areas. The waters with high densities of lar-
                 with a range of 5-7'C. Further, the scallop is induced to                vae have salinities of 32.0-32.5 and temperatures of 7-8'C
                 spawn by an abrupt rise in temperature. Spawning was                     (Fig. 17). Consequently, we have concluded that the larvae
                 observed in 1983 after a slight temperature increase, as lit-            are distributed with comparatively high densities in particular
                 tle as 1 *C, at the bottom, as a result of rough weather (Figs.          waiter masses of the coastal waters.
                 13, 14).


                                                                                     42







                              RAUSU                                            SHIBETSU                                             BEKKAI
                          40-
                          30 -
                          20 -
                   ><     10 -
                            0
                          40
                          30.
                          20 -
                   S      10 -      0100%
                           0
                              APR.         MAY              JUN.     JUL.        A              M                 J       J           A              M                J          J
                                        I          F YEAR                   0           1  5                   \9
                      WATER TEMPTA)MI.                                                                                          0
                            0                                                                                     8                                         8
                                                                                       3                          7
                                C                                9         10 -      2                            6                                        7
                                                              @8                                                  5            10 -
                          10                                                                                                          2 3 4           537
                   C=         10       2    3 4     4 567       7          20  -                0

                                                                                             Figure 12
                                                        Changes in gonad index and water temperature in Nemuro Straits, 1982.




                   The results mentioned above are preliminary, and more                                Citations
                detailed research will be undertaken. However, industrial
                spat collection in the Nemuro Straits has been successful since                         Fujii, K., and Y. Sato
                1982, thanks in part to the results of this research project.                                1977 Characteristics of primary production in the cold region waters.
                   At present, offshore spat collection is indispensable to                                       Rep. Fish. Res. Invest. Jpn. Gov. 20:25-46 [in Jpn.].
                scallop production in Japan. Some research has been per-                                Ito, H.
                                                                                                             1988 Sowing culture of scallop in Japan. In Sparks, A.K. (ed.), New
                formed to establish efficient methods for offshore scallop                                        and innovative advances in biology/engineering with potential for use
                spat collection, and some information has been obtained on                                        in aquaculture; Proceedings of fourteenth U.S.-Japan meeting on
                scallop spawning habits, larval distribution, and environmen-                                     aquaculture, p. 63-69. NOAA Tech. Rep. 70, U.S. Natl. Oceanic
                tal conditions. In some regions, industrial spat collection is                                    Atmos. Adm., Natl. Mar. Fish. Serv.
                presently successful after the results of our project in the                                 1989a Concept in mariculture of Japanese scallop. Scallop (Kushiro)
                                                                                                                  2:89-97 [in Jpn.].
                Nemuro Straits; however, successful methods for spat                                         1989b Scallop mariculture and fisheries in Japan. Scallops: Biology,
                collecting in other regions need to be established.                                               ecology and aquaculture. Elsevier Sci. Publ., Amsterdam.
                                                                                                        Kawamata, K., Y. Tamaoki, and A. Fuji
                                                                                                             1981 Gonad development of the cultured scallops in Funka Bay. J.
                Acknowledgments                                                                                   Hokkaido Fish. Exp. Sm. (Hokusuisi Geppo) 38:132-145 [in Jpn.).
                                                                                                        Kinoshita, T.
                                                                                                             1935 "Hotate-gai saibyo shiken" [An experiment on natural spat col-
                The author wishes to express sincere thanks to the follow-                                        lection of Japanese scallop]. Rep. Hokkaido Fish. Exp. Sm.
                ing coworkers of a special team: Messrs. T. Fujimoto,                                             (Hokusuisi Junpo) 273:1-8 [in Jpn.].
                T. Sasaki, H. Moriya, T. Ikeda, T. Abe, and Y. Nakata for                               Komaki, S.
                their "Jingi" friendship.                                                                    1975 "Senkai gyojo kaihatsu to gaikai joken" [Development of the
                                                                                                                  coastal fishing ground and conditions of offshore water]. Suiri-
                                                                                                                  kogaku ser. 75-B-5 [in Jpn.l.
                                                                                                        Maru, K.
                                                                                                             1972 Morphological observations on th veliger larvae of a scallop,
                                                                                                                  Patinopecten yessoensis (JAY). Sci. Rep. Hokkaido Fish. Exp. Sm.
                                                                                                                  14:55-62 [in Jpn.].
                                                                                                             1976 Studies on the reproduction ofa scallop, Patinopectenyessoen-
                                                                                                                  sis (JAY) - 1. Reproductive cycle of the cultured scallop. Sci. Rep.
                                                                                                                  Hokkaido Fish. Exp. Stn. 18:9-26 [in Jpn., Engl. abstr.]






                                                                                                  43







                                                         A                                                                                B
                                                       KUNBETSU                                                                           ICHANI
                                                       40                                                                                 40
                                                       30

                                                       20                                                                                 20
                                                                                                                                          0



                                                       10
                                                                                                                                          10
                                                       4U                                                                                 40
                                                <      30                                                                                 30
                                                z
                                                0
                                                0      20                                                                                 20
                                                       10         0@ "100%                                                                10
                                                                  APR.            MAY                   JUN.                                   APR.                MAY                 JUN.
                                                       0                                       6                   8                      0                                                   8.
                                                       5                  2    3                                   7WATER                 5                                4
                                                       0                                                           TEMPERATURE            10                 3                          7
                                                E      15                                             6                 oc                15

                                                CL
                                                w      0                                                                                  0                                                    31.88
                                                                                                                                                                                                10
                                                                                                                                                                                               3
                                                                                                                                            3'              =32                                 2
                                                                                                                   0                      5 3,@46
                                                       5     -31.8                                                 32.2
                                                             32D                                                        SALINITY          10 31.8:-@,
                                                       10    -32.2                                                      5/.0                32.2i
                                                       15    -                                                                            15        1                                         32.2
                                                                                                                   32.4                                   124              3Z2           3"
                                                                                     32.4             32.6





                                                                                         MAY 21, 1983                                                                            25,1983
                                                                                     %                  --                                A-
                                                                       -----         SCOO

                                                                                                                   0                5(lm'

                                                             K
                                                             B T                      ICHANI
                                                       0
                                                                                  6


                                                                                  4
                                                                                                        WATER                      110
                                                  10                              3.7,,                 TEMPERATURE
                                                                                                                   oc                                                      5
                                             E    20                                                               ROUGH WEATHER   :20                             4.8     B
                                                                  A                    B                                                  0    A
                                                       0                                                                                                   %               32.2
                                             CL                                                                                                             %
                                             LU
                                             In
                                                                                                      31.5         SALINITY
                                                                                                                                   10
                                                  10                                                               %o
                                                                               32.5
                                                                                                 32.0              DATE                                                    32.2
                                                                                                                   DiRECTION SC@E
                                                                                                                              2
                                                                                                                   21 AYN
                                                                                                                   22   E     2
                                                  20                                                               23   N     5    120                             32.2
                                                                                                                   24   N     5
                                                                  A                    B                           25   NE    4
                                                                                                                   26   Sw    I                A



                                                                                                                   Figure     13
                                                                          Changes in gonad index relative to sea conditions off Shibetsu, 1983.
                                                                                               6

                                                                                                                                                                           4
                                                                        a2                                                                       @@@37
                                                                               3                      7

                                                                                                      6



























                                                             N-
                                                             E SU

















                                                                                                                                                                           '32 2

                                                                                                                                                                   322












                                                                                                                        44










                                              FIGURE NO. 1                                   2                                   3                                  4
                               UE8CTsu DATE: 19 APRIL                                  25 A                                29 A                              4 MAY
                                              ,'SYMBOLIZED
                                  Imul        INDICATION
                                              I OF
                            KU                BOTTOM
                            BE                TEMPERATURE
                            KOTANUKA          @@ 0 E@ A. 5 06,
                                   RUI&B      1'0 <A. 50C                          0   0                    Qi)
                                              SAMPLING                                   0
                            N-     CHANI      SITE
                                                 OF
                                     SHIBETSU ADULT
                                              SCALLOPS
                                                                             000
                            0

                            0     5           10
                                                          5             000,                 6                                   7                                  8
                                                      9 M         0                      0 M                               11 M                                16 M


                                                                         &0      0                          &

                                                                                                                                                                0


                                                          9                                 10                                 11                                  12
                                     000 18M                                            19 M                               21 M                                25 M

                                              00                                                                                                     0  0


                                     ooO 13                                                 14                                  15                                  6
                                                     26 M                               28 M                               30 M                0 0 01 JUN1E
                                                                                                             00                          0   0
                                              00                          0                                      00                                  0  0
                                                                      0*0         0                                                             0
                                                                          0    0   0  0                     (@o                                   0
                                                                               0
                                                                  00                     Figure 14                         1                                   16
                                                                                       2(1                                 21                                4,1
                                                                                       C
                                     \111n*B
                                                                               (:)o
                                                                            00






                                                                         C
                                     ULU
                                              00





                                              0 U 21



                                                                                                                     0
                                                                                                                                                    0U1J



                                                                                                                                                        0
                                     1000                             00
                                                                          *0                                                                         0
                                                                          0 0                                                                   0
                                                                                                                                                  0
                                                                        00
                                                                               oe







                                              Horizontal changes in bottom temperatures of adult scallop habitat off Shibetsu, 1983.






                                                                                              45












                                   EXPERIMENT STATION




                                                                               n. m.

                                                          -0              0.                COASTAL
                                                                                             WATER
                                                                        20                                                                                                        0
                                        RE                                               OCEANIC
                                                                        1A01              WATER
                                                                        t I             x x x
                                       ICKANI                           60-
                                                                                                           ls@-100                                   a
                                          TOKCYrM,I                                                         30                                      x

                                    N          FUREN              K SU                                                                       x
                                        o 5 Ion....



















                                                                0






                                                                                                                                                                                              6






















                                                                                                            Figure 15
                                                                        Weekly changes in density of scallop larvae in Nemuro Straits, 1982.








                                                                                                                  46




		
				Figure 16
	Daily changes in density of scallop larvae off Shibetsu, 1982.



1987a Studies on the reproduction of a scallop, Patinopecten yessoensis		Tsubata, F.
	(JAY)- 2. Gonad development in 1-year-old scallops. Sci. Rep.			1982 "Mutsu-wan hotate-gai gyogyo kenkyu-shi" [A history of the 
	Hokkaido Fish. Exp. Stn. 20:13-26 [in Jpn., Engl. abstr.].			    	fisheries researches of the Japanese scallop in Mutsu Bay]. Aomori
1978b Studies on the reporduction of a scallop, Patinopecten yessoensis			Prefecture, 120 p. [in Jpn.].
	(JAY)- 3. Observations on hermaphroditic gonads. Sci. Rep. Hok-		Wakui, T., and A. Obara
	kaido Fish. Exp. Stn. 20:27-33 [in Jpn., Engl. abstr.].				1967 On the seasonal change of the gonads of scallop, Patinopecten
1985  Ecological studies on the seed production of scallop, Patinopecten		yessoensis (JAY), in Lake Saroma, Hokkaido. Bull. Hokkaido Reg.
	Yessoensis (Jay). Sci. Rep. Hokkaido Fish. Exp. Stn. 27, 53 p. [in		Fish. Res. Lab. 32:15-22 [in Jpn.,Engl. abstr.].
	Jpn., Engl. abstr.].									Yamamoto, G.
Maru, K., and Y. Nakagawa										1943 Gemetogenesis and the breeding season of the Japanese com-
1979  "Hotate-gai gaikai saibyo shiken" [Researches for offshore spat			mon scallop, Pecten (Patinopecten) yessoensis JAY. Bull. JPN. Soc.
	Collection of Japanese scallop]. Annu. Rep. for 1978, Avashiri Fish		Sci. Fish. 12:21-26 [in Jpn., Engl. synop.].
	Exp. Stn., hokkaido, p. 139-149 [in Jpn.].						1964 Scallop culture in mustsu Bay. Suisan Zoyoshoku Sosho 6,77
Osanal, K., S. Hirai, and M. Odashima								p. [in Jpn.].
1980 Sexual differentiation in the juveniles of the scallop, Patinopecten1	Yamamoto, G., S. Ito, N. Nishikawa, and A. Fuji
	yessoensis. Bull. Mar. Biol. Stn. Asamushi 16(4):21-230.				1971 "Hotat-gai yoshoku no shinpo" [Development of the Japanese
Shiogaki, M., S. Aoyama, E. Kitano, H. Sugawa, and Y. Uemura				scallop culture]. Complete mariculture in shallow waters. Koseisha
	1980 "Gaikai hotate-gai saibyo shiken" [Experiments on offshore spat		koseikaku (Tokyo), p. 198-263 [in Jpn.].
	collection of the Japanese scallop]. Annu. Rep. 9, Aquacul. Cent.,
	Aomori Prefec., p. 78-81 [in Jpn.].


47







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                                                                                                        A       I A A                                            100"@ N < 300
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                                                                                    WATER TEMPERATURE                                                            OC


                                                                                                                Figure 17
                                                       Relationships among larval density, water temperature, and salinity in Nemuro Straits, 1982.
                                                                                                                        A A









































































                                                                                                                  48






             Enhancement of                                                             The state of Washington has about 2,700 miles of marine
                                                                                        shoreline and major stocks of molluscan shellfish yielding
             Molluscan Sheffish                                                         over 30 million pounds annually. Between 1950 and 1985,
                                                                                        the State's population increased from 2.3 to 4.3 million peo-
             in Washington Stalt-Itcho;                                                 ple. At the same time, the demand for shellfish increased
                                                                                        by a factor of about four due to increasing recreational and
                                                                                        commercial use. At present, demand far exceeds the, sup-
                                                                                        ply. To fill the need, effort has been directed to increasing
             RONALD E. WESTLEY1                                                         stocks of shellfish, and this report describes enhancement
             NEIL A. RICKARD                                                            methods being employed by the Washington State Depart-
             Shelyish Division                                                          ment of Fisheries for three different clam fisheries.
             Washington Department of Fisheries                                            Geoducks are large (up to 10 pounds) clams found primar-
             Olympia, Washington 98504                                                  ily subtidally, but also low on intertidal beaches. This clam
                                                                                        has long been popular on intertidal sport beaches, and is
             C. LYNN GOODWIN                                                            harvested commercially (up to 5 million pounds per year)
             ALBERT J. SCHOLZ                                                           by divers. The primary factor limiting geoduck harvest is
             Pt. Whitney Shelosh Laboratory                                             its very slow natural recruitment rate, although the clams
             Washington Department of Fisheries                                         grow to commercial size rapidly. This creates an opportun-
             Brinnon, Washington 98320                                                  ity for enhancement through artificial seeding of the clam
                                                                                        beds, and we are developing a hatchery system initially aimed
                                                                                        at doubling current harvest levels.
             ABSTRACT                                                                      Razor clams are a very popular sport clam taken along 60
                                                                                        miles of intertidal ocean beach. Harvest is by hand-digging
             The Washington Department of Fisheries has undertaken aug-                 at low tide. Digging pressure has more than doubled during
             mentation of natural stocks of three clam species. We are apply-           the past 35 years, while clam setting has markedly decreased
             ing new enhancement methods in an optimal environment for                  on about one-third of clam beds. One method used to increase
             molluscan shellfish to meet increasing seafood demands. The                the abundance of clams is to transplant naturally produced
             approach taken in each case has been to carefully evaluate both            razor clam seed from subtidal areas of high abundance to
             biological and economic aspects of enhancement and to select               the low-abundance areas on intertidal beaches.
             the method that best fits the particular circumstances. The work              Hardshell clams are highly prized by sport and commer-
             carried out demonstrates that a variety of techniques are avail-           cial users. Clam abundance remains generally good, but
             able (hatchery seeding, transplantation of natural seed, and               demand far outdistances the supply. One of the major limita-
             habitat improvement). However, it also clearly demonstrates                tions on stocks is lack of suitable habitat for larval settle-
             that the more comprehensive the initial assessments can be, the            ment and growth. These clams require a sand-mudgravel
             greater the chances of success.                                            mix, and will not grow on mud or sand flats. The Washington
                                                                                        Department of Fisheries and the industry are developing tech-
                                                                                        niques for creating new clam beaches by spreading a layer
                                                                                        of gravel 4-8 inches thick on non-clam producing beaches.
                                                                                        High success occurs when beaches are careftilly selected.


                                                                                        Geoducks


                                                                                        During the summer of 1967, the Washington Department of
                                                                                        Fisheries began surveying the shallow subtidal region of
                                                                                        Puget Sound to determine the extent of the geoduck resource.
                                                                                        These surveys, conducted by SCUBA divers, have continued
                                                                                        to the present time. From the beginning of the surveys, large
                                                                                        numbers of geoducks Panope abrupta, formerly generosa,
                                                                                        were found, justifying harvest of this unexploited resource.
                                                                                        In 1969, the Washington State Legislature provided for a
                                                                                        commercial geoduck fishery beginning in 1970. Current law
                                                                                        limits the fishery to divers using hand-held gear and to waters
                                                                                        greater than 18 feet deep and further than 200 yards from
              'Deceased July 1989.                                                      the mean high-tide line.

                                                                                   49







                Distribution and abundance                                                               1980          3,910,192
                Geoduck clams are found in North America from Alaska to                                  1981          4,290,127
                California, with the population center in Puget Sound and                                1982          5,303,081
                British Columbia. Large populations of geoducks have also                                1983          3,523,450
                recently been reported in Japan. Survey results for geoducks                             1984          4,421,265
                in Puget Sound are as follows:                                                           1985          4,109,000
                                                                 Geoducks
                                                    Acres     (million pounds)        Enhancement
                Observed geoduck beds               33,799                            A geoduck hatchery and juvenile grow-out facility is oper-
                Major and commercial beds           19,545          280               ating at the Point Whitney Shellfish Laboratory, Washing-
                Commercial beds                      8,378           165              ton Department of Fisheries. The hatchery and its operation
                Annual harvest from                                                   are financed through the Washington Department of Natural
                  commercial beds                 200-300              5              Resources from sales of geoduck harvest rights to commer-
                                                                                      cial fishermen. The primary goal of the hatchery system is
                                                                                      to restock harvested subtidal geoduck beds with cultured
                Life history                                                          seed. Artificial seeding, if successful, could greatly reduce
                Geoducks are    the largest-known burrowing clam in the               the time-interval between crops from individual beds. The
                world. In Puget Sound adult clams weigh an average 1.9                first large-scale plantings were in 1985, when 250,000 seed
                pounds, and may reach 10 pounds. A geoduck begins life                were planted, and in 1986 when 1.6 million seed were
                in the spring, when spawning adults release millions of               planted. The long-range goal is to increase production in the
                gametes into the water. For 3-5 weeks, larval clams drift             hatchery until 30 million seed/year are available for plant-
                with the currents and may be transported far from the parental        ing to support an additional 5-million-pound harvest each
                bed. They soon lose their ability to swim, settle to the bot-         year.
                tom, and burrow into the substrate, usually down to 2-3 feet,         Hatchery Young clams (6-12 years old) are preferred for
                as they grow. Burrowing ceases as clams reach adult size.             brood stock because of better quality eggs. Spawners are
                  The major factor limiting geoduck production is the very            brought into the hatchery from December to July to coin-
                slow rate at which new clams are recruited into the popula-           cide with the natural spawning season. Spawning is accom-
                tion. Although the clams grow rapidly, it takes 15-60 years           plished by stimulation with high-density algae. The larvae
                for a harvest population to be replaced naturally.                    are normally ready to metamorphose 20-21 days after
                  Geoducks are commercially harvested from subtidal beds              fertilization.
                by divers using hand-held water jets. The water jet used to             During the first 10 days, the larvae are fed a combination
                harvest the clams is a short pipe (- 18 inches long) with             of Chaetocerus calcitrans and Tahitian Isochrysis. After col-
                5/8-inch diameter tip at the digging end, and a shut-off valve        lection on a 120-1d screen, they are fed a mixture of 70%
                on the other. Geoducks are harvested individually. The                7halassiosira pseudonana, 20% Tahitian Isochrysis, and
                animal is located by its "show" (neck extended out of the             10% Dunaliella tertiolecta.
                substrate), or by feeling for depressions in the substrate left
                when the neck is withdrawn. The nozzle, placed next to the            Field planting The commercially harvested beds being
                show, liquifies the substrate immediately around the clam,            replanted with hatchery seed are all subtidal, so the standard
                allowing the geoduck to be pulled out.                                method of intertidal clam reseeding furing a low tide cannot
                  An experienced diver harvesting a good bed can dig a                be used. Two basic methods of subtidal seeding are: 1) Hand
                geoduck in 15-30 seconds, and may harvest up to 2,000                 planting by divers (good only for small experimental plots),
                pounds per day under ideal conditions. Following is a sum-            or2) surface planting from boats, allowing the seed to fall
                mary of geoduck harvests in Puget Sound, 1970-85:                     to the bottom where they attach and burrow.
                                   Year             Pounds                             We have developed a geoduck seeder mounted on the back
                                                                                      of a 28-foot boat. The seed is placed in a cone-shaped tank
                                   1970               82,236                          with seawater injected at the bottom. Eight siphons carry the
                                   1971             610,250                           suspended seed in equal amounts, via plastic hoses, to the
                                   1972             493,140                           eight distribution nozzles, each 4 feet apart. Seeding is ac-
                                   1973             463,994                           complished by running the boat over the area to be seeded
                                   1974             803,358                           in long transects. Each pass covers a strip about 40 feet wide.
                                   1975           2,372,271                           Aliquots of seed are dumped into a cone tank as the boat
                                   1976           5,365,898                           proceeds down the transect line. By varying the number of
                                   1977           8,646,746                           aliquots per unit of time and the speed of the vessel, the
                                   1978           7,089,656                           density of seed reaching the bottom can be controlled. We
                                   1979           5,228,215                           normally plant between 10 and 20 seed/m2.

                                                                                 50







               The water currents and water depth affect lateral drift of           environment, they grow while subjected to tremendous
             the seed as it settles through the water column. The settling          natural mortality. They also move, either voluntarily or in-
             speed of the seed is directly related to seed size. Clams 8            voluntarily, toward the beach. Some of the survivors are
             min in length settle through the water at a rate of 7 cm/              deposited on to the unstable high-energy intertidal beach as
             second.                                                                5-15 min juveniles. Within a year, the survivors are 2-2.5
               Predation during seeding has been a major concern. How-              inches in length and are recruited into the fishery the next
             ever, significant loss of the seed as it passes through the water      year as 4-4.5 inch clams.
             column has not occurred, even though various types of poten-              During the past 35 years, intertidal razor clam stocks have
             tial predators have been present during seeding. After land-           steadily declined due to intense harvest, inconsistent natural
             ing on the bottom, the seed must burrow rapidly to avoid               reproduction and reduced setting, and recent disease mor-
             surface-feeding benthic predators such as flounders, soles,            talities. In 1979 the Washington State Legislature directed
             crabs, snails, and starfish. Burial time is inversely related          that new efforts be undertaken to offset this decline, including
             to seed size. Seed 1-2 mm in size will become burried in               enhancement of clam stocks to increase the number of razor
             4-5 minutes; 10-min seed requires up to 30 minutes for                 clams available. One method being attempted is to seed inter-
             burial. During the first 2 years of life after planting, the seed      tidal areas of depressed natural clam abundance with large
             is susceptible to such predators as starfish, crabs, and               numbers of juveniles obtained from subtidal areas.
             moonsnails, that can dig into the substrate and attach the
             juvenile clams. After 2 years, the clams are normally buried           Enhancement
             deeply enough in the substrate to be free of predation.
               Seed survival after 2 years in small experimental plots has          The large populations of juvenile razor clams on recreational-
             varied from 0 to 40 %, with most experiments averaging                 ly inaccessible subtidal beds provide a potential source of
             between 2 and 5 %. Predation is thought to be the primary              seed for replanting intertidal sport beaches. Initial work in-
             reason for losses, although predator exclosures, such as               volved developing gear and techniques to harvest the seed
             screens and cages, have not increased survival. Seed size,             and transfer it to intertidal beaches, and then surveying the
             substrate type, particle size, and compaction appear to be             nearshore area for major beds of seed clams.
             important to survival. Seed of 3-8 min shell length at plant-             To harvest the seed clams, a small hydraulic-airlift har-
             ing have never shown survival greater than 5%. Of seed                 vester was developed. The clams are separated from the sand
             averaging 13.5 mm shell length, 40% survived in one experi-            substrate by water jets and then lifted to the surface by an
             ment in a compact muddy area; but only 1. 35 % survived                airlift. Harvest is from a 34-foot boat in shallow waters 10-40
             in a soft sandy area.                                                  feet deep during calm seas. The seed harvested is 5-15 min
               Seed growth after planting varies according to the area              in length.
             planted, but can be very rapid. Planted seed can reach 2                  In late July 1985, 21 tows were made in 6 days of harvest-
             pounds in 4 to 5 years.                                                ing. A total of about 9000 juvenile razor clams were har-
                                                                                    vested. Six tows on 6 August yielded over 6.3 million
                                                                                    juveniles while the next day, 7 August, eight tows produced
             Razor clams                                                            over 15.5 million juveniles. These high recoveries demon-
                                                                                    strated the potential feasibility of the harvest method.
             The Pacific razor clam Siliqua patuld inhabits Washington's               Subsequently, a special survey was undertaken to deter-
             open, wave-swept coastal beaches from the mouth of the                 mine the extent of this available resource. Juvenile clam
             Columbia River north to the Quinault River, and on small               densities were found to be highest in the vicinity of the
             isolated beaches north to Cape Flattery. It supports an in-            northern beaches. Between 6 August and 10 October, 84 tows
             tensive recreational fishery on the Washington coast. His-             yielded over 127 million juvenile razor clams. Of these, 93
             torical annual harvest effort has been about 700,000 digger            million were transplanted to the beaches south of Grays
             trips, yielding approximately 1.3 million pounds of clams.             Harbor, Twin Harbors, and Long Beach. Based on these
                                                                                    surveys, it was conservatively estimated that there were ap-
             Life history                                                           proximately 28 billion juvenile clams present in the 5-kM2
                                                                                    subtidal area near Iron Springs where maximum densities
             The Pacific razor clam is found in North America from cen-             exceeded 13,000/m2. Later harvests in early October pro-
             tral California to Alaska, with the largest population avail-          duced over 19 million juvenile clams per day which aver-
             able for recreational harvest occurring in Washington. Local           aged 5 min (range 1-15 mm).
             razor clams may live 5-8 years; however, most are harvested               At the end of each day's harvest, the seed clams are taken
             by age-3. Reproductive maturity occurs by age-2, and spawn-            ashore and manually planted on the beach at low tide. Several
             ing usually takes place in late spring. Larval survival and            experimental planting methods were tried. The most success-
             distribution are dependent on both favorable ocean currents            ftil was to place the seed in large buckets and pour the con-
             and weather conditions.                                                tents on the sand ahead of an advancing wave. Although the
               Settlement of juvenile clams into the substrate occurs in            seed clams dig into the sand within minutes, planting is best
             very large numbers subtidally. In this comparatively stable            done at night on an incoming tide to minimize dessication

                                                                                51







               and predation. Even with this manual method, large plant-             4 Avoidance of areas with major abundances of known clam
               ings can be accomplished in a short time-period.                      predators.
                  The harvest method is clearly successful and cost effec-
               tive. The unknowns are:                                                  Cost of graveling is variable but is estimated to be about
               I What is the survival of the planted clams? Studies are              $12,000 per acre. When in production, each acre should have
               underway to assess survival. Early indications are that ade-          an annual yield of 15,000 pounds of clams.
               quate survival occurred.
               2 Will subtidal sets occur with sufficient regularity to make
               this a useful technique? If seed is available at least once in
               3 years, it will be viable. If seed is available only once in
               10 years, it would be of limited value. In 1988, nearly 3.3
               million juvenile clams were again harvested from the area
               near Iron Springs. These clams were also transplanted to the
               beaches south of Grays Harbor. Therefore, preliminary in-
               dications are that subtidal seed will be available at least once
               every 3 years.


               Hardshell clams


               Sport utilization of hardshell (manila and native littleneck)
               clams has increased from about 250,000 user trips in 1950
               to over 1 million in 1985. Commercial production has more
               than doubled. Total harvest currently is about 4.8 million
               pounds per year. Since one major limitation to production
               of these highly valued clams is lack of the needed sand-mud-
               gravel substrate for settlement and survival of clam larvae,
               there is a major focus on modifying new beach substrate to
               increase production. Starting in the 1960s, the industry, and
               more recently the Washington Department of Fisheries, have
               embarked upon beach enhancement by spreading 1-8 inches
               of gravel over previously unsuitable habitat to create new
               clam ground.
                 The gravel used is a mixture of rock measuring 1/4-inch
               up to a maximum of 3 inches in diameter. Normally, gravel
               is hauled-in by barge, dumped at high tide, and then spread
               mechanically at low tide. It normally takes a minimum of
               3 years after placement before clam production begins.
                 Major factors in successful clam production include:
               I Selection of areas where good populations of free-swim-
               ming clam larvae are present.
               2 Selection of areas where the gravel will stay effectively
               in place for at least 20 years. Areas of excessive storm (wave)
               exposure and of heavy silt deposition or major longshore cur-
               rent should be avoided.

               3 Avoidance of areas with heavy organic loading in the
               existing substrate. Placement of gravel in these conditions
               usually results in production of hydrogen sulfide and will
               foul the ground for 2-4 years. It is also wise to avoid areas
               of dense eelgrass or seaweed. At the very least, graveling
               should be done when stands of grass are at a seasonal mini-
               mun. Freshwater run-off can result in siltation of gravel plots
               when combined with poor upland management.


                                                                                 52






             The Role of                                                                 Decreases in shellfish stocks, whether resulting from over-
                                                                                         fishing, parasites, predators and disease, or unusual environ-
             Aquaculture                        in                                       mental perturbations, often prompt management agencies to
                                                                                         encourage or implement stock enhancement programs. These
             the Restoration                                                             programs have as an ultimate goal either the rebuilding of
                                                                                         depleted fishery stocks, or the augmentation of natural stocks
             and Enhancement of                                                          to support an artificially high maximum sustainable yield.
                                                                                         The shellfisheries of North America have not traditionally
             Molluscan Fisheries in                                                      relied upon restoration or enhancement programs to augment
                                                                                         wildstock populations. Fishery practices, such as the trans-
             North America'                                                              location of seed from natural beds to grow-out areas or the
                                                                                         regular replanting of shellstock as cultch during periods when
                                                                                         natural set is occurring, have long been part of the oyster
                                                                                         industry (Beaven 1953, Tarver and Dugas 1973, Reisinger
             JOHN J. MANZI                                                               1978, Dugas 1984). Similar activities, albeit on a more
             Marine Resources Research Institute                                         limited scale, have been practiced with other bivalves in-
             P.O. Box 12559                                                              cluding the sofishell clam, hard clam, and scallop (Turner
             Charleston, South Carolina 29412                                            1951, Dow 1953, Mackenzie 1979).
                                                                                           Recently, the success of large commercial-scale mollusk
                                                                                         aquaculture operations and the continued decline of wildstock
                                                                                         resources have prompted an evaluation of the use of inten-
             ABSTRACT                                                                    sive aquaculture in the restoration and/or enhancement of
                                                                                         wildstock fisheries. This paper will provide a survey of mol-
             The natural populations of most commercially important species              luscan aquaculture technology applicable to restoration or
             of bivalve mollusks continue to decline in North America. As                enhancement programs, with particular attention to the use of
             these stocks decline and their commercial and recreational values           hatcheries as a fishery management tool and the role of gene-
             increase, aquaculture becomes an appreciably more attractive                tics in molluscan fishery enhancement. To place the prob-
             alternative for the restoration and/or enhancement of molluscan             lem in perspective, we will first address two case histories
             fisheries populations. The historical uses of aquaculture to ini-
             tiate, and eventually supplement, the Pacific oyster fishery in             involving management practices influencing mollusk fisheries.
             the northwestern United States and British Columbia provide
             a good model for the development of fisheries management                    A case history: Oyster culture
             through the intercession of aquaculture. This paper reviews two             in the Pacific Northwest
             approaches to the incorporation of aquaculture in the manage-
             ment of restoration or enhancement of molluscan fishery stocks:             Aquaculture has played a significant role in the oyster in-
             (1) Use of hatcheries as management tools, and (2) the role of              dustry of North America. Postset and seed of the American
             genetics in mollusk fishery enhancement. Both approaches have               oyster, Crassostrea virginica, have been produced by hatch-
             significant potential for mollusk fisheries, but both are prone             ery and nursery systems for many years. This stock en-
             to an eventuality which can include long-term detrimental im-               hancement had been relatively small until recently when set,
             pacts on fishery populations. The inevitable conclusion is that,            produced by commercial culture, has made a significant
             provided we learn from previous mistakes of the salmonid
             fisheries, both hatchery production and genetic manipulation                impact in certain parts of the United States. The oyster
             of resource populations can provide significant relief to the               industry of Long Island epitomizes this impact. At present,
             molluscan fisheries of North America.                                       one hatchery on Long Island provides nearly a third of the
                                                                                         total oyster seed planted in western Long Island Sound.
                                                                                         Hatchery-produced set are reared in trays suspended from
                                                                                         rafts until they attain a size of 10-15 mm. The seed are then
                                                                                         broadcast over prepared bottom for grow-out.
                                                                                           Although an appreciable dependence between hatchery/
                                                                                         nursery-produced seed and the oyster fishery of Long Island
                                                                                         Sound has been demonstrated, development of the Pacific
                                                                                         oyster, Crassostrea gigas, fishery and its continued exist-
                                                                                         ence depends on commercial aquaculture participation. For
                                                                                         many years, no wildstock fishery for the Pacific oyster ex-
                                                                                         isted on the west coast of North America. All oysters were
                                                                                         grown to market size from seed imported from Miyagi and
               'Contribution no. 300 of the South Carolina Marine Resource Center.       Kumamoto prefectures in Japan. In the 1960s, C gigas began

                                                                                    53






                  appearing in significant natural spatfaUs in Washington State                                            Table I
                  (A.K. Sparks, Alaska Fish. Cent., Nall. Mar. Fish. Serv.,                     Percentage of clams in spawning and spent stages of gametogenesis
                  NOAA, 7600 Sand Point Way N.E., Seattle, WA 98115-                            in native and transplanted populations of hard clams, Mercenaria
                  0070, pers. commun., Oct. 1986). These spat, along with                       mercenaria, in Great South Bay, New York (data from Kassner and
                  those produced through commercial hatcheries, have sup-                                               Malouf 1982).
                  plied a greater and greater proportion of the seed used in                                   Native clams (%)          Spawner transplants
                  the Pacific oyster grow-out industry (Chew 1979). The con-
                  tribution of seed from hatchery intervention has become                       Elate        Spawning        Spent       Spawning          Spent
                  significant. One hatchery in Washington State produced 18                     -
                  billion spat in 1986 (J. Donaldson, Coast Oyster Co.,                         6/21/78          0               0            0               0
                                                                                                6/25/78          18              0            35             20
                  Quilcene, WA, pers. commun., Oct. 1986) and will supply                       7/07/78          13             85            5             100
                  seed to grow-out facilities from Quilcene Bay, Washington,                    7/20/78          0             100            0             100
                  to Humboldt Bay, California. The same hatchery has helped                     8/10/78          0              60            0              75
                  develop and standardize methods of transporting late-stage
                  or "eyed" oyster larvae for setting in other locales. This
                  technique of "remote setting" has expanded the industry con-
                  siderably by providing a low-cost, on-site seed producing                  negligible. They indicate that typical annual transplants in-
                  capability to the growers of the Pacific Oyster.                           volve about 500 to 1,000 bushels (18-36 m3) of chowder
                                                                                             clams. Assuming there are about 250 clams/bu (7,000 clams/
                  A case history: Spawner transplanting                                      m3), a typical operation would transplant 250,000 clams,
                  of the hard clam                                                           one-half or 125,000 or which would be females. If it is also
                                                                                             assumed that an average gamete release of Great South Bay
                  Great South Bay on the southern shore of Long Island, New                  female chowder clams is 106 eggs (Bricelj and Malouf
                  York, is the largest producer of the hard clam, Mercenaria                 198 1), then one could expect a maximum of 7.5 X 1011
                  mercenaria, in the world. This one fishery produces about                  larvae introduced to the system by the spawner transplants.
                  $20 million annually (Kassner and Malouf 1982) from land-                  Extrapolating from the data of McHugh (1981) who estimated
                  ings that average about 400,000 bushels a year. The impor-                 egg production from natural clam populations in the eastern
                  tance of this fishery is demonstrated by the number of                     half of the Bay, we find that a total larval production for
                  management practices applied by state and local regulatory                 the entire Bay may well exceed 11.0 X 1011 per year. It
                  agencies. Among these are limitations on daily harvests,                   would appear that the spawner transplants would contribute,
                  fishing gear, and minimum marketable sizes, as well as                     at best, no more than 0.005 % of the total annual larvae pro-
                  restoration programs involving the planting of seed clams                  duction in Great South Bay.
                  and/or the transplanting of ripe spawners into the Bay dur-                   Adthough this analysis of spawner transplants in Great
                  ing spawning seasons (Bricelj and Malouf 1981, McHugh                      South Bay is less than encouraging, the concept of introduc-
                  198 1). The rationale behind the spawner transplants is based              ing spawners to provide larvae for areas devoid of clams is
                  on the belief that highly fecund spawners introduced to the                reasonable. Spawner transplants do have the capacity of
                  Bay from a more northern area would result in greater                      providing seed to limited areas where larvae would not
                  recruitment. It was thought an increase in recruitment would               normally present.
                  come about for two reasons: Spawners would add more lar-
                  vae to the Bay milieu, and the spawning of the transplants                 Hatcheries as a management tool
                  would be asynchronous-spawning later than the native
                  stock. The combined result of this introduction would thus                 A paradigm of fishery management states that population-
                  be not only an increase in the total quantity of larvae avail-             enhancement programs cannot consistently and predictably
                  able to the year-class but also an increase in the length of               benefit fishery populations that are regulated by density-
                  time that larvae would be in the Bay and exposed to favor-                 independent factors. If, however, (1) a fishery population
                  able environmental conditions for settlement.                              is regulated by density-dependent factors, (2) the environ-
                    Recently, Kassner and Malouf (1982) performed a study                    ment is capable of sustaining introduced additions to this
                  evaluating the benefits of spawner transplants in Great South              population, and (3) it is technically possible to produce large
                  Bay. Their results, reported in Table 1, invalidate the                    numbers of high quality seed on an economical basis, then
                  assumption that the introduction of spawners serves to in-                 hatcheries can be used to effectively intercede in fisheries
                  troduce larvae at a time when they would not otherwise be                  restoration and management activities.
                  available from native stocks, at least during the year this study             The success of finfish hatcheries in the augmentation of
                  was performed.                                                             salmonid populations has stimulated interest in hatchery pro-
                    If spawner transplanting does not provide larvae to the                  duction as a management tool in molluscan fisheries (Malouf
                  Great South Bay system when they would not otherwise be                    1989). Augmentation of natural populations has a long history
                  present, can it significantly supplement the natural set?                  in the mollusk fisheries. Traditionally, seed transplanting pro-
                  Kassner and Malouf (1982) suggest that the contribution is                 grams, particularly for oysters, have been part of most fish-

                                                                                        54







            eries on the eastern seaboard. In these fisheries, shellfish seed        sterile adults. This was an important result for the fishery,
            are taken from public or privately owned seed beds to areas              because it has traditionally suffered during periods when the
            where recruitment is low but growth and survival are ex-                 resource was reproductively mature (ripe and spawning). An
            cellent. The seed beds are restocked annually with shell or              oyster with ripe gonads was unattractive for the half-shell
            other cultch, normally at a time when shellfish are setting,             trade, and subsequently the market and price were depressed
            to replenish the set and seed for future transplants.                    in the spawning season. With the advent of triploid oysters
              In the northeastern United States hard clam seed is often              and their characteristic lack of gonadal tissue, an opportun-
            planted by townships to augment natural clam populations                 ity developed to introduce a resource that would be attrac-
            and improve recreational and commercial fishing. As exam-                tive to the half-shell trade during the spawning season. The
            ples, townships in Massachusetts and New York typically                  first commercial quantities of triploid C gigas spat were pro-
            purchase 4-6 mm seed clams from commercial hatcheries                    duced in 1984, and the first harvest of market-size oysters
            and utilize field nursery systems (rafts, cages, etc.) to grow           has a high consumer acceptance and that the substitution of
            the seed out to planting size (20-25 mm). These programs,                triploids for diploid C. gigas is an effective resource man-
            however, are limited by the length of time available for ef-             agement tool (Jim Donaldson, Coast Oyster Co., Quilcene,
            fective field nursery culture and the availability of suitable-          WA, pers. commun., Oct. 1986).
            size seed in the early spring. Recently, at least one township             Other examples of genetic manipulation of mollusks
            in New York (Brookhaven) has begun buying young postset                  include the production of disease resistance in oyster popu-
            clams (0.5 mm) and using a land-based upflow nursery to                  lations and the genetic selection of shell markings for the
            produce the 5-min seed for their field nursery system. Over-             production of identifiably distinct clams for restocking pro-
            all, the seed planting programs of the Northeaster United                grams. The outbreak of MSX (Halplospofidium nelsoni) and
            States are relatively small, and their value to the fisheries            subsequent decline of the oyster fishery in Delaware Bay in
            they were implemented to augment is questionable. A thor-                the 1960s prompted the establishment of a breeding program
            ough evaluation of the planting programs has not been per-               to produce disease-resistant oysters. The project has selected
            formed, and the factors influencing the potential success of             for MSX-resistant survival for several generations and has
            such programs are not well understood.                                   produced oysters for restocking that are many times more
              In an analysis of two planting programs in New York and                resistant than natural stocks (Ford and Haskin 1982). The
            Massachusetts, Malouf (1989) concluded that clam seed                    general interest in restocking programs by management agen-
            planting programs of undetermined value should not be con-               cies has led to the production of seed with external char-
            sidered as benign at worst. These programs can result in the             acteristics allowing the easy identification or segregation of
            neglect of other management tools, the introduction of disease           introduced populations. An obvious question applied to stock-
            organisms or exotics, the possible reduction of genetic vari-            ing programs is their real value in the contribution to the
            ability in natural stocks, and the possible degradation of               commercial or recreational harvest. Without a mechanism
            growth rates and survival in natural populations by exceed-              to identify the stocked populations, the actual contribution
            ing the carrying capacity of local environments. While it is             can only be speculated. In South Carolina, a project has been
            presently difficult to justify the use of hatcheries to bolster          initiated to determine the benefits of restocking public shell-
            declining commercial landings, it does appear that hatcheries            fish grounds with hard clam, Mercenaria mercenaria. In
            can play a proper role in molluscan fishery management.                  order to determine the impact of such stocking programs and
            Malouf (1989) stated that, as part of an integrated manage-              allow comparisons between introduced and native popula-
            ment program with realistic goals, hatcheries and other cul-             sions, it was necessary to provide seed stock distinguishable
            ture systems can be used to help establish or reestablish self-          from the native population. This was accomplished by cross-
            sustaining populations in localized areas, sustain recreational          ing local clams with the "notata" variety of the same species.
            fisheries in intensively harvested areas, and provide a mech-            This variety has alternate bands of light and dark on the shell,
            anism for allowing the genetic improvement in fishery stocks.            making it easily differentiated from native stock. The shell
                                                                                     markings have been demonstrated to be controlled by a single
            Genetics in molluscan fisheries                                          gene, or several closely linked genes, inherited as a Mendel-
            enhancement                                                              ian unit (Chanley 1961, Humphrey and Walker 1982). The
                                                                                     seed generated through this cross has a very high percent-
            Aside from the obvious benefits of improving growth and                  age (80%) of notata coloration and will thus be segregat-
            survival of molluscan stocks through genetic intervention,               able from native wildstock which typically has less than 1 %
            manipulation of the genetic architecture of molluscan popu-              of the total population displaying notata markings.
            lations can provide tools of significant value to fishery man-             A final example of genetic manipulation in molluscan fish-
            agement. A good example is the recent development of                     eries is the recent work with heterozygosity in marine bivalve
            triploid Crassostrea gigas and their incorporation into the              populations. Several reviews have brought considerable
            Pacific oyster fishery of Washington State (Chaiton and Allen            attention to the relationship between multiple-locus enzyme
            1985). Although it appears that triploidy does not impart                heterozygosity and growth rate (Koehn and Gaffney 1984,
            significantly faster growth in oyster seed (Stanley et al. 198 1),       Gaffney and Scott 1985). Additional research has implcated
            it does interfere with gametogenesis, resulting in functionally          improved survival and/or vigor with increasing heterozy-

                                                                                55






                   gosity (Rodhouse and Gaffney 1984). These data have stim-                            Chaiton, J.A., and S.K. Allen
                   ulated the initiation of a breeding program to improve growth                            11985 Early detection of triploidy in the larvae of Pacific oysters,
                   and survival in hatchery-reared populations of the hard clam,                              Crassostrea gigas, by flow cytometry. Aquaculture 48:35-43.
                                                                                                        Chanley, P.E.
                   M. mercenafia, in South Carolina. This program incorpor-                                 1%]. Inheritance of shell markings and growth in the hard clam, Venus
                   ates three breeding schemes to produce improved stocks:                                    mercenaria. Proc. Nad. Shellfish. Assoc. 50:163-169.
                   Hybridization (with M. campechiensis), selected breeding,                            Cheiv, K.K.
                   and outcrosses of inbred lines to induce increased enzyme-                               11979 The Pacific oyster (Crassostrea gigas) in the West Coast of the
                   locus heterozygosity. The lines produced through these out-                                United States. In Mann, R. (ed.), Exotic species in mariculture.
                                                                                                              Mass. Inst. Technol. Press, Cambridge, 249 p.
                   crosses performed better than parental lines in overall growth                       Dillon, R.T., Jr., and J.J. Manzi
                   over the first 12 months of culture but have not demonstrated                            1987 Hard clam, Mercenaria mercenaria, broodstocks: Genetic drift
                   increased heterozygosity. When compared with correspond-                                   and loss of rare alleles without reduction in heterozygosity. Aqua-
                   ing wild populations in regard to allele frequencies at seven                              culture 60:99-105.
                    olymorphic enzyme loci, the outcrossed lines showed evi-                                :1988 Enzyme heterozygosity and growth in nursery populations of
                   p                                                                                          the hard clam, Mercenaria mercenaria. J. Exp. Mar. Biol. Ecol.
                   dence of genetic drift and loss of rare alleles. These crosses                             116:79-86.
                   obviously resulted in the production of fast-growing lines                           Dow, R.L.
                   that were genetically distinct from the parental stock (Dillon                           1953 An experimental progrina in shellfish management. Fish. Circ.
                   and Manzi 1987). Further analysis indicated that there were                                10, Maine Dep. Sea Shore Fish., Augusta, Me, I I p.
                   highly significant differences at individual enzyme loci in                          Dugas, R.
                                                                                                            .1984 New findings may spur state's oyster production. Louisiana
                   the largest and smallest clams from each cross (Dillon and                                 Conversationists, Nov-Dec, p. 4-7.
                   Manzi 1988). These results would be consistent with the                              Ford, S.E., and H.H. Haskin
                   hypotheses that the alleles themselves were not effecting                                1982 History and epizootiology of Haplosporidium nelsoni (MSX),
                   growth or were related to linkage disequilibrium. It appears                               an oyster pathogen in Delaware Bay, 1957-1980. J. Invertebr.
                   instead that alleles are marking the entire parental genone                                Pathol. 40:118-141.
                                                                                                        Gafl'ney, P.M., and T.M. Scott
                   and that variation in growth rates of offspring from indivQ                              1985 Genetic heterozygosity and production traits in natui-Al and hatch-
                   parents are masking a possible relationship with overall                                   ery populations of bivalves. Aquaculture 42:289-302.
                   heterozygosity. This work is increasing the understanding                            Humphrey, C.M., and R.L. Walker
                   of genetic variation in hatchery-reared seed and may allow                               1982 The occurrence of Mercenaria mercenaris form notata in Georgia
                   more efficient and better-directed breeding programs for the                               and South Carolina: Calculation of phenotypic and genetypic frequen-
                                                                                                              cies. Malacologia 23(l):75-79.
                   production of molluscan seed stocks.                                                 Kassner, J., and R.E. Malouf
                                                                                                            1982 An evaluation of "spawner transplants" as a management tool
                   Summary                                                                                    in Long Island's hard clam fisheries. J. Shellfish REs. 2(2):165-172.
                                                                                                        Koehn, R.K., and P.M. Gaffney
                   Through the use of case histories and reviews of recent and                              1984 Genetic heterozygosity and growth rate in M)Wlus edulis. Mar.
                   ongoing research programs, this survey provided a brief                                    Biol. 82:1-7.
                   recapitulation of the use of aquaculture, particularly hatch-                        Mackenzie, C.L., Jr.
                   eries and genetic manipulation, in molluscan fisheries man-                              1979 Management for increasing clam abundance. Mar. Fish. Rev.
                                                                                                              41(10):10-22.
                   agement. In summary, aquaculture-related fisheries manage-                           Malouf, R.E.
                   ment activities have significant potential for the mollusk                               1989 Hatcheries as a management tool in clam fisheries. In Manzi,
                   fisheries of North America. Concentrating management pro-                                  J., and M. Castagna (eds.), Clam mariculture in North America, p.
                   grams in these activities can, however, result in neglect of                               448-461. Elsevier Sci. Publ., Amsterdam.
                   other management tools and can lead to reduction of genetic                          McHugh, J.J.
                                                                                                            1981 Recent advances in hard clam mariculture. J. Shellfish Res.
                   variability in natural stocks and the possible degradation of                              l(l):51-56.
                   growth rates and survival in local natural populations when                          Reisinger, A.E., Jr.
                   introduced stocks exceed environmental carrying capacities.                            1518 Demonstrate revitalization of oyster beds by resurfacing andreseed-
                   As part of an integrated fisheries management program,                                     ing. Fourth quarter and summation report, Contract 10740077, Coastal
                   aquaculture can provide significant latitude in management                                 Plains Reg. Comm., Coastal Resourc. Div., Brunswick, GA, 25 p.
                                                                                                        Rodliouse, P.G., and P.M. Gaffney
                   options and can provide mechanisms for realistic stock im-                               1984 Effect of heterozygosity on metabolism during starvation in the
                   provements in fishery populations.                                                         Amerian oyster, Crassostrea virginica. Mar. Gol. 80:179-187.
                                                                                                        Sbudey, J.G., H. Hidu, and S.K. Allen
                   Citations                                                                                1981 Polyploidy induced in the American oyster, Crasstrea virginica,
                                                                                                              with cytochalasin B. Aquaculture23:1-10.
                   Beaven, G.F.                                                                         Tarver, J.W., and R.J. Dugas
                        1953    A preliminary report on some experiments in the production                  1973 Experimental oyster transplanting in Louisiana. Tech. Bull.
                          and transplanting of South Carolina seed oysters to certain waters                  7, Louisiana Wildl. Fish. Comm., New Orleans, 6 p.
                          of the Chesapeake area. Proc. Gulf Caribb. Fish. Inst. 5:115-122.             Turner, H.J., Jr.
                   Brice1j, V.M., and R.E. Malouf                                                           1951 Third report on investigations of methods of improving the
                        1981 Aspects of reproduction of hard clams (Mercena?ia mercenaria)                    shellfish resources of Massachusetts. Report to the Committee of
                          in Great South Bay, New York. Proc. Natl. Shellfish. Assoc. 70(2):                  Clam Technicians, Atlantic States Marine Fisheries Comniission. Con-
                          216-229.                                                                            trib. 564, Woods Hole Oceanogr. Inst., Woods Hole, MA, 5 p.


                                                                                                  56






             Application of LHRH-a                                                    It has become essential in current aquaculture practice to con-
                                                                                      trol the reproductive cycle of cultivated fish in captivity. The
             Cholesterol Pellets to                                                   traditional method of collecting fry from nature for aqua-
                                                                                      culture purposes is gradually being replaced by production
             Maturation of Finfish:                                                   of fry in the hatchery. Another objective of hatchery fry
                                                                                      production is for release into the ocean for stock enhance-
             MWish                                                                    ment or for ocean ranching, as in the case of salmon and
                                                                                      many species cultured in Japan. These goals depend on the
                                                                                      successful maturation and spawning of adult fish in captivity,
                                                                                      as well as on larval rearing. Unfortunately, these processes,
             CHENG-SHENG LEE                                                          particularly spawning, occur sporadically in most cultured
             CLYDE S. TAMARU                                                          species.
             Oceanic Institute                                                          The purpose of induced spawning is to bring about the final
             Makapuu Point                                                            stage of maturation in both males and females. In males, this
             Waimanalo, Hawaii 96795                                                  stage includes spermiation and ejaculation. In females, it
                                                                                      includes the migration and breakdown of the germinal vesi-
                                                                                      cle, hydration, ovulation, and oviposition. Many researchers
                                                                                      have reviewed the techniques currently used to induce spawn-
             ABSTRACT                                                                 ing (Harvey and Hoar 1979, Lam 1982, Donaldson and
                                                                                      Hunter 1983, Scott and Sumpter 1983, Lam 1985). Success-
             One step toward the goal of stock enchancement of a particular           ful spawning can be achieved in most cases by a variety of
             species is the control of its maturation in captivity. Many culti-       methods including the use of hormones. After fertilized eggs
             vated finfish species, however, do not complete the reproduc-            are obtained, larvae are hatched and reared in a hatchery.
             tive cycle in captivity. Hormone therapies have been used to             The standard procedure for larval feeding begins with
             overcome the physiological barriers that inhibit completion of           rotifers, brine shrimp, and/or copepods and is followed by
             the reproductive cycle. Acute or chronic hormone administra-
             tion is often used to deliver various hormones or steroids to the        a formulated feed. These procedures were reviewed by
             fish. The slow and sustained release of LHRH to trigger the              Kuronuma and Fukusho (1984) and Fulcusho (1985).
             secretion of endogenous hormones is one hormone therapy at-                Spawning can be induced and viable larvae produced only
             tracting more attention.                                                 after the fish reach a certain stage of maturity. Some fish
               The application of LHRH and its analogues and their potency            species, however, either do not complete or even begin
             for manipulating the reproductive activities of various fish,            maturation in captivity. Techniques for inducing maturation
             especially milkfish (Chanos chanos), is documented in this               are still under development.
             report.                                                                    Induced maturation requires a more prolonged period
                                                                                      (weeks to months) of hormone therapy than induced spawn-
                                                                                      ing. Hormone therapies are used to induce maturation by
                                                                                      overcoming the physiological barriers posed by lack of
                                                                                      necessary environmental stimuli. Environmental cues are
                                                                                      known to play an important role in regulating reproduction
                                                                                      and mediating the secretion of hormones which synchronize
                                                                                      the activities of various organs into an orchestrated physio-
                                                                                      logical and biochemical response. An effective hormone
                                                                                      therapy must combine the most productive hormone formula-
                                                                                      tion with the proper administration strategy. Among the
                                                                                      available hormones and methods, LHRH, incorporated in
                                                                                      a cholesterol pellet for implantation, has attracted increased
                                                                                      attention (Donaldson and Hunter 1983, Crim 1985, Lam
                                                                                      1985).
                                                                                        In this report, we discuss the technologies for administer-
                                                                                      ing LHRH and document its potency for advancing and
                                                                                      accelerating maturation and the reproductive cycle and for
                                                                                      synchronizing spawning of various fish species. Finally,
                                                                                      milkfish will be used to illustrate the potency of LHRH-a
                                                                                      in inducing the maturation and spawning of important
                                                                                      cultured fish.



                                                                                 57





                                             Table 1                                     Administration of LHRH
                                        Structure of LHRH.
                                                                                         Modes of administration also affect the potency and half-life
                           pGlu-His-Trp-Ser-Tyr-Gly-Leu'-Arg'-Pro-Gly-NH2                of LHRH in the fish. Crim (1985) discussed different ad-
                                         Mammalian LHRH                                  ministration methods, and other experiments were conducted
                           pGlu-His-Trp-Ser-Tyr-Gly-Trp'-Leu'-Pro-Gly-NH2                to compare different application strategies (CTHAP 1977,
                                                                                         Weil and Crim 1983, Kouril et al. 1983). LHRH/LHRH-a
                                           Salmon LHRH                                   can be delivered to the fish at different body sites and using
                                                                                         diff@rent vehicles. Injections can be made intracranially,
                                                                                         intraperitoneally, and intrapericardially or intramuscularly.
                                                                                         CAHEF (1975) indicated that effective dose of LHRH in
                 Luteinizing hormone-releasing                                           most cultured carp species was lower when delivered by
                 hormone (LIEM                                                           intracranial injection than with intraperitoneal of intramus-
                                                                                         cular injection. Only slightly better results were found with
                 The hypothalamus-pituitary-gonad axis is known to be the                intracranial injection than with intraperitoneal injection for
                 neuro-endocrine control route for fish reproduction (Donald-            inducing ovulation in goldfish (Lam et al 1976). Kouril et al.
                 son 1973, Lam 1985). The hypothalamus controls the secre-               (1986) conducted experiments with tench (Tinca tinca) and
                 tion of gonadotropin-releasing hormone (GnRH) which acts                found that there was no difference in the number of spawned
                 on the pituitary, causing it to release gonadotropin. Activ-            fish. between intrapericardial and intramuscular injection of
                 ities in the hypothalamus are controlled by environmental               LHRH-a.
                 and/or hormonal factors, a process which usually takes a long             The vehicle used to deliver hormones to fish determines
                 time to initiate. Theoretically, direct administration of GnRH          the rates of release and diffusion of the hormones and, con-
                 should shorten the time required to release gonadotropin.               sequently, the release and diffusion rates of gonadotropin.
                 Research has been conducted to identify the structure of                LHRH and its analogue have been administered to fish in
                 GnRH in fish (Sherwood et al. 1983, 1984). These research-              either liquid or solid form. The liquid form consists of LHRH
                 ers concluded that mullet, milkfish, trout, and salmon all con-         dissolved in 0. 8 % NaCl solution or in 40 % propylene glycol.
                 tain chromatographically and immunologically identical pep-             Administration of this form results in a rapid initial increase
                 tides (Table 1). The structure differs from porcine (Matsuo             of the circulating hormone level but it is not sustained. Aida
                 et al. 1972) and ovine (Burgus et al. 1972) LHRH in two                 et al. (1978) prolonged the release of LHRH for a few days
                 aniino acids in positions 7 and 8 of the decapeptide (Table 1).         by -using a viscous liquid vehicle. They prepared an emul-
                   LHRH has since been synthesized in the laboratory, based              sified solution of synthetic LHRH in Freund's adjuvant.
                 on this proposed structure, and has proven effective in                 Administration of the hormone in solid form sustains hor-
                                                                                         mone release from weeks to months. Chronic LHRH ad-
                 stimulating the release of gonadotropin and in inducing ovula-
                 tion in mammals, chickens, and amphibians (see review by                ministration devices have been prepared in the form of either
                 Lam et al. 1976).                                                       a silicone rubber implant or cholesterol pellet. Both methods
                   Although LHRH was first proven to stimulate the secre-                elirninate the need for frequent injections, thereby decreas-
                 tion of gonadotropin in the common carp, Cyprinus carpio                ing stress.
                 (Breton and Weil 1973), its potency is many times less than               Preparation of LHRH silicone rubber implants has been
                 the synthetic nonapeptide LHRH (CTHAP 1977). Chinese                    described by Lotz and Syllwasschy (1979). Kent et al. (1980)
                 scientists were able to induce ovulation in cultured carp               described a cholesterol matrix pellet suitable for delivery of
                 with synthetic LHRH analogue. Several types of LHRH-a                   LHRH-a. This method was further modified by Lee et al.
                 are available and have been tried on fish. These include                (1985, 1986c) to meet specified experimental needs. The
                 des-Gly'O[D-Ala6]-LHRH ethylamide; des-Gly10[D-LeU6]_                   basic composition of the LHRH-a cholesterol pellet is 95 %
                 LHRH ethylamide; des-Blyl0[D-Ser(BU1)6]-LHRH ethyla-                    cholesterol, 5 % cocoa butter, and approximately I % of the
                 mide; des-Gly'O[D-Trp6]-LHRH ethylamide and des-Gly10                   above total as LHRH-a. Following the procedures established
                 [D-Phe6l-LHRH ethylamide. From an in vitro study con-                   byLee et al. (1986b), each pellet weighs 20 mg, measures
                 ducted by Coy et al. (1975), luteinizing hormone (LH) and               2.4 nun in diameter and 5.0 min in length, and contains 200
                                                                                             "HRH
                 follicle-stimulating hormone (FSH)-releasing activities of the          pgL        -a. A bioassay study on this pellet was conducted
                 LHRH-a are ten times that of LHRH. The analogues also                   on trout by Dr. L.W. Crim (Memorial Univ., Newfound-
                 have a longer half-life due to a slow rate of enzyme degrada-           land, Canada). Pellets were implanted intraperitoneally (IP)
                 tion (Buckingham 1978). Marks and Stem (1974) also stated               or intramuscularly (IM) in rainbow trout. Blood from each
                 that des-Gly'O[D-Ala6]-LHRH ethylamide is less readily                  fish was sampled on day 1 (the day of implantation) and again
                 broken down by brain enzymes than LHRH.                                 at 1, 2, and 4 weeks after implantation. Gonadotropin levels
                                                                                         in blood serum showed a rapid elevation and remained at
                                                                                         a higher level than in the control group for up to 4 weeks
                                                                                         (Fig. 1).


                                                                                    58







                                                                                The potency of LHRH-a, when used to accelerate the
                14.0                                                          maturation process, is inconsistent among species. LHRH-a
                     Control Sham                                             has been successfully used to induce ovulation and spawn-
               12.0 -0 IM                 100 @Ug            200 jig          ing, however, in many fish species. These include:
                     13 lp                                                    Acipenseridae (Doroshov and Lutes 1984); Anguillidae
               10.0 -Chinese D-Ala LHRH                                       (Research Group of Eel Reproduction 1978); Cyprinidae
                     El im
                                                                              (CTHAP 1977); Mugilidae (Lee et al. 1987); Plecoglossidae
                8.0 .    lp
                                                         _X                   (Hirose and Ishida 1974); Serranidae (Barnabe and Barnabe-
                                                                              Q
             o                                                                  uet 1985, Harvey et al. 1985); Siganidae (Harvey et al.
                                                                              1985); and Soleidae (Ramos 1986). Spawning success was
                 4.0                                                          improved, however, by combining LHRH-a with other
                                                                              ovulatory agents such as: carp pituitary for mullet (Lee et
                 2.0
                                                                              al. 1987); 17 a-hydroxy-20fl-dihydroprogesterone for carp
                  0                                                           (Breton et al. 1983), coho salmon and rainbow trout (Jala-
                       1 2 4  1 2 4     1 2 4  1  4       1 2 4 1 2 4         bert et al. 1978); and pimozide for goldfish, common carp,
                    day I            Elapsed Time (.eeks)                     trout, catfish, and loach (see review by Lam 1985).
                                                                                Pimozide potentiates the ovulatory effect of LHRH-a by
                                     Figure I                                 blocking the action of dopamine which can mimic gonado-
           Gonadotropin levels in trout after receiving a sham pellet or LHRH-a tropin-releasing inhibitory factor (GnRIF). Pimozide can
                                       pellet.                                either be administered with LHRH-a or separately to the reci-
                                                                              pient fish. Billard et al. (1984) preferred to apply pimozide
                                                                              prior to LHRH. Sokolowska et al. (1984), however, con-
           LHRH and the reproductive                                          cluded that the occurrence of ovulation in goldfish was high
           cycle in fish                                                      when pimozide was injected prior to or in conjunction with
                                                                              injections of LHRH-a. De Leeuw et al. (1985) indicated that
           Although LHRH did not elicit any change in prespawning             the minimum effective dosage for inducing ovulation in
           landlocked salmon's pituitary GtH content (Weil and Crim           African catfish could be as low as 5 mg pimozide combined
                                                                              with 0.05 mg LHRH-a per kg body weight. Lin et al. (1985)
           1983), LHRH and its analogue have proven effective in              and Billard et al. (1984) have also conducted dose-response
           increasing plasma GtH levels in many other fish species (see       studies on pimozide and LHRH-a used to induce spawning
           review by Lam 1982, Donaldson and Hunter 1983). Eleva-             in loach and brown trout.
           tion of the GtH level results in maturation and spawning of          Studies on the use of LHRH-a for fish reproduction have,
           fish. Many researchers, therefore, began using LHRH-a to           thus far, concentrated on freshwater species. Recently, a
           replace conventional HCG and fish pituitary. The response          research group at the Oceanic Institute in Hawaii has at-
           of fish to LHRH-a varies, however, according to the stage          tempted to control the reproduction of milkfish, Chanos
           of gonadal development at which the fish receives the hor-         chanos, a euryhaline fish, by application of LHRH-a.
           mone (Crim et al. 1983a). In prespawning salmon, ovula-
           tion and spermiation were accelerated by LHRH-a treatment,
           but in sexually regressed male salmon, spermatogenesis was         LHRH-a and milkfish
           not induced by the same treatment. The LHRH-a treatment            reproduction
           accelerated vitellogenic development during the rapid phase
           of gonadal recrudescence, but reduced the GSI value in male
           salmon. Crim and Glebe (1984) induced early spawning in            Maturation
           30 % of the female Atlantic salmon given LHRH-a 45 days            The milkfish, an important food fish in Southeast Asia,
           prior to the normal spawning season, and in 94% of the             especially in the Philippines, Taiwan, and Indonesia, rarely
           females treated 28 days before. LHRH-a cholesterol pellet          matures and spawns in captivity. Development of a reliable
           treatment did not result in accelerated maturation or spawn-       method for controlling maturation and spawning in milkfish
           ing in grey mullet when given approximately 60 days prior          has been investigated for a number of years (Lam 1984, Kuo
           to the spawning season (Lee and Tamaru 1988). Ovulation            1985). The problems remain unsolved, however. Recent
           in spring-spawning rainbow trout was advanced by 3 to 4            studies carried out by Lee et al. (1986a,b,d) indicate that
           weeks, however, when fish were implanted about 2 months            LHRH-a has a positive effect on both maturation and spawn-
           before the spawning season (Crim et al. 1983b). The spawn-         ing in milkfish.
           ing season in sea bass was advanced by 40 days using an
           LHRH-a injection under natural conditions (Barnabe and
           Barnabe-Quet 1985).




                                                                          59











                             100
                                   Control                      Crystalline                             too      Control
                                                                Testosterone
                                                                                                                 Treatment 1
                                                                & LHRH
                      Z       50                                                                        80       Treatment 2
                                                                                 9/12
                      M                              7/10
                                                                                                        60
                                                                                 4/8
                                0                    1/8
                      LL
                      -                                                                               -6 40
                      0      100
                                                                Liquid T   stosterone                 A
                                   LHRHa
                                                                   LHRHa                                20                                                   j
                                                                                 9/10
                              50
                                                                                                          01
                      4)
                      CL                             3/9
                                                                                                               Jan   Feb     Mar    Apr    May     Jun     Jul    Aug
                                                                           7     8/8
                                                     5/11               F  11
                                             n                                n".                                           % Maturation Male (1986)
                               0 f--                                          "'A
                                       >      c- c-                 >      c- c-
                                              c  C                 -9      C  C
                                                                        ZZ                                                      Figure 3
                                                         Months                                   Maturation of male milkrish in control and treatment groups during
                                                                                                                               1986 season.
                                                 Figure 2
                  Percentage of fish that reach maturity in response to different hormone
                  therapies. Solid bar indicates females; blank bar indicates nudes. Frac-
                  tions represent the number of mature fish to the total number of sexed            In the LHRH-a and liquid MT therapy, two mature females
                                 fish. (Condensed from Lee et al. 1986b).                         were also found in the month of April. The number of mature
                                                                                                  females increased steadily during the course of the experi-
                                                                                                  ment. By July, almost 90% of the individuals were found
                                                                                                  to be mature.
                     As mentioned, induction of the maturation process requires                     When LHRH-a was combined with MT in crystal form,
                  a prolonged period (weeks to months) during which circulat-                     a high percentage of running ripe males were found by June.
                  ing levels of the desired hormone must remain elevated.                         A relatively low number of mature females was found in this
                  Among the varous methods of administration, the LHRH-a                          particular hormone therapy. Overall, 65% of individuals
                  cholesterol pellet has accelerated the reproductive cycles of                   undergoing this treatment matured by the end of July (after
                  landlocked salmon (Crim et al. 1983a), rainbow trout (Crim                      4 months of treatment). Only one female from the control
                  et al. 1983b), and Atlantic salmon (Crim and Glebe 1984).                       group reached maturity (possessed 0.7 mm oocytes) during
                  In our 1985 milkfish maturation study, LHRH-a cholesterol                       the course of the experiment, attaining this state in July. Four
                  pellets were applied alone or in conjunction with 17a-methyl-                   males were found to possess milt as early as April. This
                  testosterone. The three hormone therapies used were: Choles-                    number declined steadily until the month of July, when there
                  terol pellets containing 200 Mg of LHRH-a (LHRH-a pellet)                       was a dramatic increase. Therefore, the combination of
                  or combinations of LHRH-a pellets plus silastic tubing con-                     LHRH-a pellet with liquid MT capsules appeared to enhance
                  taining either 250 pg of dissolved 17a-methyltestosterone                       the maturation of milkfish.
                  Giquid MT capsule) or 10 mg crystal 17a-methyltestosterone                        In order to validate the effectiveness of LHRH-a pellets
                  (crystal MT capsule).                                                           and liquid MT capsules, this combined hormone therapy was
                     Experimental groups of 20 milkfish each received one of                      applied to 80 fish beginning in March 1986 (as Treatment
                  these three therapies beginning in March, while a fourth con-                   1) and in April (as Treatment 2). The 20 other fish in this
                  trol group received placebo implants. LHRH-a pellets were                       study received placebo implants and served as controls.
                  administered monthly; crystal MT capsules were admin-                           Maturation of males was not significantly enhanced by this
                  istered once; and liquid MT capsules were administered                          hormone therapy (Fig. 3). By June, however, 90% of the
                  twice, at the beginning of the experiment and three months                      females possessed eggs larger than 50 ym compared with
                  later. The application of the LHRH-a pellet alone was less                      about 35% in the control group (Fig. 4). These results
                  effective in inducing maturity in males but appeared to                         demonstrated that a combination of LHRH-a pellet and liquid
                  enhance the total number of females that reached maturity                       MT capsule will enhance the maturation of female milkfish.
                  (Fig. 2). Mature females were found as early as April. The
                  combination of LHRH-a and MT, in either crystal or liquid
                  form, resulted in a significantly higher number of mature
                                                                           a
                                                                           U


















































                  individuals by the month of July when compared with all
                  of the other treatments (Fig. 2).




                                                                                            60








                 too   0 Control                                                                               Pellets@l@ Injection                        0
                       0 Treatment 1                                                            10 -
                                                                                                          Response
                 80    0 Treatment 2
                                                                                                      E] No Response
                                                                                                E
                 60                                                                             CL
                                                                                                ID


                 40
                                                                                                4


                 2
                                                                                                Z



                   0
                                                      ..;      :                                E
                   0
                                                                                                2
                                            r       [II                  @' _@11`11
                       Jan     Feb    Mar     Apr   may      Jun    Jul   Aug
                                      % Maturation Female  (1986)                                                   Jun     Jul      Aug    Sept   Oct    Nov
                                                                                                                         Months (1985)
                                          Figure 4                                                                      Figure 5
             Maturation of female mWnh in control and treatment groups during
                                         1986 season.                                      Frequency of successful and unsuccessful induced spawnings of milk-
                                                                                           fish, attempted April-November 1985. Two strategies were employed
                                                                                           in inducing final maturation and spawning: 1) LHRH-a cholesterol pellet
                                                                                           implants, and 2) LHRH-a liquid injections. (From Lee et a]. 1986b).

             Spawning
             The formulation of a standardized method to induce milkfish                        10 -
             to spawn has eluded investigators for over a decade (Lam                                El Response
             1984, Kuo 1985). Initially, spawning attempts involved ad-                         8 -     No Response
             ministering piscine pituitary extracts (salmon or carp), plus                           El
                                                                                                S
             HCG (Vanstone et al. 1977, Juario et at. 1979, Kuo et al.                          26 -
                                                                                                Z
             1979, Liao et al. 1979). More recently, HCG has been used                          "6
                                                                                                t4
             alone to bring about the final maturation of ova (Tseng and
             Hsiao 1979; Lin 1982, 1984). In all previous attempts,
                                                                                                Z
             however, fertilized eggs were obtained by manual stripping                         2
             of both females and ripe males for their gametes. This ac-                         0             F 715
             tion usually resulted in the loss of broodstock, in only a single                        p I      P I       P I       P I       P t       P 1
                                                                                                    650-700   700-750 750-800 800-850 850-900 900-950
             spawning per season, and in a low fertilization rate (0-60 %).                                            Egg Diameter 0Jm)
             These factors clearly underscore the need for a more reliable                 I                                                                      I
             method of inducing milkfish to spawn. This method should                                                   Figure 6
             insure a higher fertilization rate, survival of spawners after                Number of successful and unsuccessful induced spawns versus average
             spawning, and multiple spawnings.                                             egg diameters at which hormonal therapies were initiated. Results
               In many cultured species, LHRH/LHRH-a has been used                         are presented for two different modes of administration (P=pellet,
             to replace traditional ovulating agents such as HCG or piscine                               l=injection). (From Lee et al. 1986b).
             pituitary (see review by Donaldson and Hunter 1983). We
             theref6re evaluated the effectiveness of LHRH-a as a spawn-
             ing agent for milkfish, when administered in either pellet                    conducted July-November (Fig. 5). Overall, a 53 % spawn-
             implants or injections. Induced spawning was attempted when                   ing success rate was obtained using the pellet implant as a
             a female possessed an average egg diameter of 650 lAm or                      spawning agent. The fish consistently spawned about 48
             more. The maturity of males was assessed by exerting                          hours after being implanted. Nineteen of 33 attempts using
             pressure on the abdomen and observing whether or not milt                     LHRH-a administered via an injection resulted in successful
             could be extruded. In each spawning attempt, LHRH-a was
             only administered once through either intramuscular pellet                    spawnings (58% success rate). In contrast to those induced
             implantation or injection, in contrast to two or more injec-                  with pellets, successful spawnings from fish injected with
             tions in conventional spawning trials. A fixed dose of 250                    LHRH-a occurred within 20-26 hours after receiving their
             Wg, per fish was administered to all females and males receiv-                injections.
             ing hormones. Control fish were either injected with normal                        The number of successful spawnings is related to the aver-
             saline or not treated at all. A total of 50 induced spawning                  age size of eggs at which the LHRH-a was administered (Fig.
             attempts was conducted using either intramuscular pellet                      6). The number of successful spawnings appears to increase
                                                                                                                                            L

















             implatation (N= 17) or injection (N= 33). LHRH-a pellets                      with size of initial egg diameters, and 700-950 lAm is the
             were used April-July, and LHRH-a injection trials were                        optimal range. Successful splawnings occurred in fish that

                                                                                      61






                     possessed single modal distribution of egg size in some fish                     Citations
                     that possessed bimodal distributions. In the latter case, the
                     smaller clutch of eggs did not exceed 350 jAm in size. Spawn-                    Aida, K., R.S. Izumo, H. Satoh, and M. Hibiya
                     ing attempts in fish that possessed bimodal distribution of                           1978 Induction of ovulation in plaice and goby with synthetic LH
                                                                                                              releasing hormone. Bull. Jpn. Soc. Sci. Fish. 44:445-450.
                     egg sizes, where the smaller clutch exceeded 350 jAm, did                        Barnabe, G., and R. Barnabe-Quet
                     not succeed.                                                                          1985 Advancement and improvement of induced spawning in the sea
                       In the above experiment, the dosages of LHRH-a per                                     bass Dicentrarchus labrax (L.) using an LHRH analogue injection.
                     kilogram body weight in spawning attempts were 41.3 ;Ag                                  Aquaculture 49:125-132.
                     for pellet implantation and 58.7,ug for liquid injection. Ex-                    Billard R., P. Reinaud, M.G. Hoflebecq, and B. Breton
                     periments are in progress to determine the minimum effec-                             1984 Advancement and synchronization of spawning in Salmo gaird-
                                                                                                              neri and S. trutta following administration of LHRH-A combined
                     live dosage for the spawning of milkfish.                                                or not with pimozide. Aquaculture 43:57-66.
                       In summary, LHRH-a is a potent hormone for controlling                         Breton, B., J. Jalabert, K. Bieniarz, M. Sokolowka, and P. Epler
                     the reproduction activities of many finfish species. These                            1993 Effects of synthetic LH-RH and analog on plama gonadotropin
                     activities include advancing and synchronizing spawning                                  levels and maturation response to 17 -hydroxy-20 -dihydroproges-
                                                                                                              terone. Aquaculture 32:105-114.
                     increasing milt volume, and inducing spermiation. LHRH-a                         Breton, B., and C. Weil
                     cholesterol pellets induce the release and sustain higher blood                       1973 Endocrinologie comparee - effets du LH/FSH-RH synthetique
                     serum levels of GtH. The proper combination of LHRH-a                                    et d'extraits hypodWamiques de carpe sur la secretion d'hormone
                     cholesterol pellet with other hormones should control the                                gonadotrophe in vivo chez la carpe (Cyprinus carpio L.). C.R. Acad.
                     maturation of most finfish species. This technology will                                 Sci. Ser. III Sci. Vie Paris 227:2061-2064.
                                                                                                      Buckingham, J.C.
                     benefit the enhancement of natural populations and the initia-                        1978 The hypophysiotrophic hormones. Prog. Med. Chem. 15:165-
                     tion of ocean ranching.                                                                  198.
                                                                                                      Burgus, R., M. Butcher, M. Amoss, N. Ling, M. Monahan, J. Rivier,
                                                                                                        It. Fellows, R. Blackwell, W. Vale, and R. Guillemin
                     Acknowledgments                                                                       1972 Primary structure of the ovine hypothalamic luteinizing hormone-
                                                                                                              releasing factor (LRF). Proc. Natl. Acad. Sci. USA. 69:278-282.
                                                                                                      CAHEF (Conference on the Application of Hormones to Economic
                     This research was supported by a grant from U.S. AID                                Fish)
                     (DAN-4161-A-00-4055-00). We wish to thank members of                                  1975 Experiment on induced spawning of farm fishes by synthetic
                     the Finfish Program for their assistance in this research and                            LRH. Kexue Tongboe 20(l):43-48.
                     A. Belanger for preparation of the manuscript.                                   CTHAP (Cooperative Team for Homonal Application in Pisciculture)
                                                                                                           1977 A new highly effective ovulating agent for fish reproduction.
                                                                                                              Sci. Sin. 20(4):469-474.
                                                                                                      Coy, D.H., A.V. Schally, J.A. Vilchez-martinez, E.J. Coy, and A.
                                                                                                        Ariniura
                                                                                                           1975 Stimulatory and inhibitory analogs of LHRH. In Motta, M., P.G.
                                                                                                              Crosignani, and L. Martini (eds.), Hypothalamic hormones, p. 1-12.
                                                                                                              Acad. Press, NY.
                                                                                                      Crim, L.W.
                                                                                                           1985 Methods for acute and chronic hormone administration in fish.
                                                                                                              In Lee, C.-S., and I.C. Liao (eds.), Reproduction and culture of
                                                                                                              milkfish, p. 1-13. Oceanic Inst., Wainumalo, Hawaii, and Tung-
                                                                                                              kang Mar. Lab., Taiwan.
                                                                                                      Crim, L.W., and B.D. Glebe
                                                                                                           1984 Advancement and synchrony of ovulation in Atlantic salmon with
                                                                                                              pelleted LHRH-analogue. Aquaculture 43:47-56.
                                                                                                      Crim, L.W., D.M. Evans, and B.H. Vickery
                                                                                                           1983a Manipulation of the seasonal reproductive cycle of the land-
                                                                                                              locked Atlantic salmon (Salmo salar) by LHRH analogues adminis-
                                                                                                              tered at various stages of gonadal development. Can. J. Fish. Aquat.
                                                                                                              Sci. 40:61-67.
                                                                                                      Crim, L.W., A.M. Sutterfin, D. M. Evans, and C. Weil
                                                                                                           1983b Accelerated ovulation by pelleted LHRH analogues treatment
                                                                                                              by spring-spawning rainbow trout (Salmo gairdneri) held at low
                                                                                                              temperature. Aquaculture 35:299-307.
                                                                                                      D(!Leeuw, R., H.J.Th. Goos, C.J.J. Richter, and E.H. Eding
                                                                                                           1985 Pimozide-LHRHa-induced breeding of the African catfish,
                                                                                                              Clarias gariepinus (Burchell). Aquaculture 44:495-302.
                                                                                                      Donaldson, E.M.
                                                                                                           1973 Reproductive endocrinology of fishes. Am. Zol. 13:909-927.
                                                                                                      Donaldson, E.M., and G.A. Hunter
                                                                                                           1983 Induced final maturation, ovulation, and spermiation in cultured
                                                                                                              fish. In Hoar, W.S., D.J. Randall, and E.M. Donaldson (eds.), Fish
                                                                                                              physiology, vol. 9B, p. 351-403. Acad. Press, NY.


                                                                                                 62








               Doroshov, S.I., and P.B. Lutes                                                       Lam, T.J., S. Pandey, Y. Nagahama, and W.S. Hoar
                   1984 Preliminary data on the induction of ovulation in white sturgeon                1976 Effect of synthetic luteinizing hormone-releasing hormone
                      (Acipenser transmontanus Richardson). Aquaculture 38:221-227.                       (LH-RH) on ovulation and pituitary cytology of the goldfish Carassius
               Fukusho, K.                                                                                auratus. Can. J. Zool. 54:816-824.
                   1985 Status of marine larval culture in Japan. In Lee, C.-S., and I.C.           Lee, C.-S., and C.S. Tamaru
                      Liao (eds.), Reproduction and culture of milkfish, p. 126-139.                    1988 Advances and future prospects in controlled maturation and
                      Oceanic Inst., Waimanalo, Hawaii, and Tungkang Mar. Lab.,                           spawning of grey mullet (Mugil cephalus L.). Aquaculture 74:63-73.
                      Taiwan.                                                                       Lee, C.-S., C.S. Tamaru, and L.W. Crim
               Harvey, B.J., and W.S. Hoar                                                              1985 Preparation of a luteinizing hormone-releasing hormone choles-
                   1979 The theory and practice of induced breeding in fish. Int. Dev.                    terol pellet and its implantation in the milkfish (Chanos chanos)
                      Res. Cent. Publ. TS21e, Ottawa, Ontario, Canada, 48 p.                              Forsskal). In Lee, C.-S., and I.C. Liao (eds.), Reproduction and
               Harvey, B.J., J. Nacario, L.W. Crim, J.V. Juario, and C.L. Marte                           culture of milkfish, p. 215-226. Oceanic Inst., Waimanalo, Hawaii,
                   1985 Induced spawning of sea bass, Lates calcarifer, and rabbitfish,                   and Tungkang Mar. Lab., Taiwan.
                      Siganus guttatus, after implantation of pelleted LHRH analogue.               Lee,  C.-S., C.S. Tamaru, J.E. Banno, C.D. Kelley, A. Bocek, and
                      Aquaculture 47:53-59.                                                           J.A. Wyban
               Hirose, K., and R. Ishida                                                                1986a Induced maturation and spawning of milkfish, Chanos chanos
                   1974 Induction of ovulation in the ayo Plecoglossus altivelis) with                    Forsskal, by hormone implantation. Aquaculture 52:199-205.
                      LH releasing hormone (LHRH). Bull. Jpn. Soc. Sci. Fish. 40:                   Lee, C.-S., C.S. Tamaru, J.E. Banno, and C.D. Kelley
                      1235-1240.                                                                        1986b Influence of chronic administration of LHRH-analogue and/or
               Jalabert, B., B. Breton, and A. Fostier                                                    17 -methyltestosterone on maturation in milkfish, Chanos chanos.
                   1978 Precocious induction of oocyte maturation and ovulation in rain-                  Aquaculture 59:147-159.
                      bow trout (Salmo gairdneri): Problems when using 17 -hydroxy-20               Lee, C.-S., C.S. Tamaru, and C.D. Kelley
                      -dihydroprogesterone. Ann. Biol. Anim. Biochin. Biophys. 18:                      1986c Technique for making chronic-release LHRH-a and 17 -methyl-
                      977-984.                                                                            testosterone pellets for intramuscular implantation in fishes. Aqua-
               Juario, J.V., M. Natividad, G. Quinitio, and J. Banno                                      culture 59:161-168.
                   1979 Experiments on the induced spawning and larval rearing of the               Lee, C.-S., C.S. Tamaru, C.D. Kelley, and J.E. Banno
                      milkfish Chanos chanos (Forsskal) in 1971@'. SEAFDEC Aquacult.                    1986d Induced spawing of milkfish, Chanos chanos, by a single ap-
                      Dep. Q. Res. Rep. 3, Southeast Asian Fish. Dev. Cent., Philippines,                 plication of LHRH-analogue. Aquaculture 58:87-98.
                      13 p.                                                                         Lee, C.-S., C.S. Tamaru, G.T. Miyamoto, and C.D. Kelley
               Kent, J.S., B.H. Vickery, and G.I. McRae                                                 1987 Induced spawning of grey mullet (Mugil cephalus) by LHRH-a.
                   1980 The use of a cholesterol matrix pellet implant for early studies                  Aquaculture 62:327-336.
                      on the prolonged release in animals of agonist analogues of luteiniz-         Liao, I.C., J.V. Juario, S. Kumagai, H. Nakajima, M. Natividad,
                      ing hormone-releasing hormone. Presented at 7th Int. Symp. on Con-              and P. Buri
                      trolled Release of Bioactive Materials, Fort Lauderdale, Florida.                 1979 On the induced spawning and larval rearing of milkfish, Chanos
                      Inst. Pharm. Sci. Biol. Stud., Syntex Research, Palo Alto, CA 94304.                chanos (Forsskal). Aquaculture 18:75-93.
               Kouril, J., T. Barth, J. Hamackova, and M. Flegel                                    Lin, H.R., P. Chun, L.Z. Lu, X.J. Zhou, G. van der Kraak, and
                   1986 Induced ovulation in tench (7-inca finca L.) by various LH-RH                 R.E. Peter
                      synthetic analogues: Effect of site of administration and temperature.            1985 Induction of ovulation in the loach (Paramisgunius dabryanus)
                      Aquaculture 54:37-44.                                                               using pimozide and [D-Ala    6, Pro9-N-Ethylamide]-LHRH. Aqua-
               Kouril, J., T. Barth, J. Hamackova, J. Slaninova, L. Servitova, J.                         culture 46:333-340.
                 Machacek, and M. Flegel                                                            Lin, L.T.
                   1983 Application of LH-RH and its analog for reaching ovulation in                   1982 Further success in induced spawning of pond-reared milkfish.
                      female tench, grass carp, carp and sheatfish. Bul. VU'RH Vodnany                    China Fish. 320:9-10 [in Chinese].
                      2:3-16 [in Czech.].                                                               1984 Studies on the induced breeding of milkfish (Chanos chanos
               Kuo, C.M.                                                                                  Forsskal) reared in ponds. China Fish. 378:3-29 [in Chinese].
                   1985 A review of induced breeding of ntilkfish. In Lee, C.-S., and               Lotz, W., and B. Syllwasschy
                      I.C. Liao (eds.), Reproduction and culture of milkfish, p. 57-77.                 1979 Release of oligopeptides from silicone rubber implants in rats
                      Oceanic Inst., Waimanalo, Hawaii, and Tungkang Mar. Lab.,                           over periods exceeding ten days. J. Pharm. Pharmacol. 31:649-650.
                      Taiwan.                                                                       Marks, J., and F. Stern
               Kuo, C.M., C.E. Nash, and W.O. Watanabe                                                  1974 Enzymatic mechamsm, for the inactivation of luteinizing hormone-
                   1979 Induced breeding experiments with milkfish, Chanos chanos                         releasing hormone (LH-RH). Biochem. Biophys. Res. Commun.
                      (Forsskal), in Hawaii. Aquaculture 16:247-252.                                      61:1458.
               Kuronuma, K., and K. Fukusho                                                         Matsuo, H., Y. Baba, R.M.G. Nair, A. Arimura, and A.V. Schally
                   1984 Rearing of marine fish larvae in Japan. Int. Dev. Res. Cent.,                   1971 Structure of the porcine LH- and FSH-releasing hormone. I.
                      Ottawa, Ontario, Canada, 109 p.                                                     The proposed amino acid sequence. Biochem. Biophys. Res.
               Lam, T.J.                                                                                  Commun. 43:1334-1339.
                   1982 Applications of endocrinology to fish culture. Can. J. Fish.                Ramos, J.
                      Aquat. Sci. 39:111-137.                                                           1986 Luteinizing hormone-releasing hormone analogue (Lft-RHa)
                   1984 Artificial propagation of milkfish: Present status and problems.                  induces precocious ovulation in common sole (Solea solea L.).
                      In Juario, J.V., R.P. Ferraris, and L.V. Benitez (eds.), Advances                   Aquaculture 54:185-190.
                      in milkfish biology and culture, p. 21-39. Island Publ. House, Inc.,          Research Group of Eel Reproduction, Xiamen (Amoy) Fisheries
                      Metro Manila, Philippines.                                                      College and Fujian Fisheries Institute
                   1985 Induced spawning in fish. In Lee, C.-S., and I.C. Liao (eds.),                  1978 Preliminary studies on the induction of spawning in common
                      Reproduction and culture of milkfish, p. 14-56. Oceanic Inst.,                      eels. Acta Zool. Sin. 24:339-402.
                      Waimanalo, Hawaii, and Tungkang Mar. Lab., Taiwan.





                                                                                              63







                   Scott, A.P., and J.P. Sumpter
                       1983 The control of trout reproduction: Basic and applied research
                         on hormones. In Rankin, J.C., T.J. Pitcher, and R.T. Duggan (eds.),
                         Control processes in fish physiology, p. 200-220. Croorn Heim,
                         London.
                   Sherwood, N.M., L. Eiden, M. Brownstein, J. Speiss, J. Rivier, and
                     W. Vale
                       1983 Characterization of a teleost gonadotropin releasing hormone.
                         Proc. Nat]. Acad. Sci. USA, 80:2794-2798.
                   Sherwood, N.M., B. Harvey, M.J. Brownstein, and L.E. Eiden
                       1984 Gonadotropin-releasing hormone (Gn-RH) in striped mullet
                         (Mugil cephalus), nulkfish (Chanos chanos), and rainbow trout (Salmo
                         gairdnen): Comparison with salmon Gn-RH. Comp. Endocrinol.
                         55:174-181.
                   Sokolowska, M., R.E. Peter, C.S. Nahorniak, C.H. Pan, J.P. Chang,
                    L.W. Crim, and C. Weil
                       1984 Induction of ovulation in goldfish, Carassius auratus, by pimo-
                         zide and analogues of LH-RH. Aquaculture 36:71-83.
                   Tseng, L.C., and S.M. Hsiao
                       1979 First successful case of artificial propagation of pond-reared
                         milkfish. China Fish. 320:9-10 [in Chinese].
                   Vanstone, W.E., L.B. Trio, Jr., A.C. Villaluz, D.C. Ramsingh, S.
                    Kumagai, P.J. Duldoco, M.M.L. Barnes, and C.E. Duenas
                       1977 Breeding and larval rearing of milkfish Chanos chanos (Pisces:
                         Chanidae). SEAFDEC Res. Rep. 3, Southeast Asian Fish. Dev.
                         Cent., Philippines, p. 3-17.
                   Weil, C., and L.W. Crim
                       1983 Administration of LHRH analogues in various ways: Effect on
                         the advancement of spermiation in prespawning landlocked salmon,
                         Salmo salar. Aquaculture 35:103-115.












































                                                                                               64







            Trends                                                                    Over the past 25 years dramatic changes in commercial oyster
                                                                                      operations have taken place on the west coast. The most
            Oyster Cultivation                                                        significant changes are centered around the procurement of
                                                                                      seed oysters and new innovations related to the development
            on the West Coast of                                                      of desired stocks for cultivation. Further, although intertidal
                                                                                      bed culture is still the main growing technique utilized by
            North America                                                             the oyster growers, we see an expansion of off-bottom
                                                                                      cultivation.
                                                                                        The main oyster produced on the west coast at the turn
                                                                                      of the century was the Olympia or native oyster (0strea
            KENNETH K. CHEW                                                           lurida). With the decline of the native oyster industry, the
            Division of Fishery Science and Aquaculture                               eastern or American oyster (Crassostrea virginica) was
            School of Fisheries WH-10                                                 introduced for cultivation, primarily in the state of Washing-
            University of Washington                                                  ton. Survival was not good for this species and ultimately
            Seattle, Washington 98195                                                 the Japanese or Pacific oyster (Crassostrea gigas) was in-
                                                                                      troduced and became the mainstay of the present west coast
                                                                                      oyster industry. Aside from the Pacific oyster and, to a
                                                                                      limited extent, the cultivation of the Olympia oyster in re-
            ABSTRACT                                                                  cent years, efforts have been made to utilize the Suminoe
                                                                                      oyster (Crassostrea rivularis) (Breese and Malouf 1977) for
            Trends in oyster cultivation on the west coast of North America           cultivation primarily as a summer oyster. Also, efforts to
            are briefly discussed with comments on species utilized, culture          produce the Kumamoto variety of C gigas for hatchery pro-
            growout methods, remote setting of eyed larvae, and stock                 duction have met with moderate success. Later activities
            development through genetics and breeding. Although several               involved the growing of European oysters (Ostrea edulis)
            species of oysters are utilized, the Pacific oyster (Crassostrea
            gigas) constitutes over 98% of oysters produced on the west               and hybridized Miyagi and Kumamoto varieties of C gigas
            coast.                                                                    to produce what is called a gigamoto oyster. Although
              Oysters are grown mainly on intertidal bed areas. Off-bottom            smaller, the gigamoto will grow a deeper shell and provide
            culture, utilizing several techniques, is increasing but unlikely         a good shape and taste for the half-shell market. Chew (1984)
            to expand quickly because of permit-application requirements              discussed Pacific oyster production trends for Washington,
            related to the sociopolitical climate existing in most populated          California, Oregon, and British Columbia and noted that
            areas of the United States.                                               Washington is still the major producer for the west coast.
              The concept of remote setting of eyed larvae has been shown             In fact, Washington's annual production has risen from over
            to greatly enhance seed production of Pacific oysters on the west         6 million lbs (2722 MT) of meat in 1985 to 10 million lbs
            coast. Obtaining adequate Pacific oyster seed periodically from           (4537 MT) in 1989. Recent estimates of 1989 production in
            natural catches when available, backed up with a consistent               California are above I million lbs (454 MT), and British Co-
            annual catch from remote setting, makes seed production a con-
            cern of the past.                                                         lumbia and Oregon are about 0.5 million lbs (227 MT) each.
              Stock development through genetics and breeding studies                 Alaska has also begun production of Pacific oysters but at
            shows the potential for developing stocks resistant to diseases,          a much lower level.
            as well as strains with desired traits. Breeding programs can
            be developed to produce high summer carbohydrate levels in
            oysters. Essential safeguards against inbreeding problems are             Culture grow-out methods
            discussed as they relate to Pacific oysters.
              The method for producing the triploid oyster with greatly               Extensive culture with Pacific oyster seed placed on inter-
            reduced gonadal development in the summer is discussed. These             tidal beds for growout remains the major west coast produc-
            neutered oysters are expected to be in heavy demand for the               tion method, probably accounting for more than 90 %, with
            summer fresh and/or half-shell trade when regular production
            is established.                                                           the rest produced by off-bottom culture.
                                                                                        Further, Crassostrea gigas probably constitutes more than
                                                                                      98% of oysters produced on the west coast of the United
                                                                                      States and British Columbia. Figure I provides a map of the
                                                                                      major areas of natural seed production and growout of com-
                                                                                      mercial stocks from British Columbia south to California.
                                                                                      Although not shown, southeastern Alaska is also beginning
                                                                                      to produce Pacific oysters, primarily for the half-shell
                                                                                      market.



                                                                                 65








                                                                                   Stake culture occurs in several areas. Wire or wood stakes
                                                                                   with seed-bearing cultch material attached to the top are
                   Pendrell Sound                     011, N)                      placed in the lower intertidal zone.
                                                                                   Rack culture is one of the more popular type of off-bottom
                                                                                   cultivation. Racks are built in the intertidal zone and shell
                   Lasqueti Island                            Vancouver            strings are hung for production of oysters. This type of
                   Barkley Sound                                                   culture is found in all four California areas in Figure I and
                   Strait of Georgia-                      t@.                     is increasing in Willapa Bay and Grays Harbor, Washing-
                   San Juan Islands                                                ton. Alaska and British Columbia are also expanding this
                   Puget Sound                                  Seattle            culture technique.
                   Hood Canal                                 -Taco a              . Also, French plastic pipe collectors with seed can be used
                   Grays Harbor                               Olympia              in a VyW of rack culture in British Columbia and Washington.
                   Willapa Bay                                                     Double rows of line are staked on the intertidal zone and
                                                           Washington              the plastic pipes are laid across and fastened to the line.
                   Tillamook Bay                                                   Raft or floating culture The commercial use of rafts for
                                                       Portland                    hanging oyster strings continuously in the water column was
                   Yaquina Bay                                                     initiated more than 20 years ago in southern Puget Sound,
                                                                                   but has not expanded for a variety of reasons. Aside from
                                                         Oregon                    minimal biological concerns, there are problems with secur-
                                                                                   ing permits for such applications through governmental agen-
                   Coos Bay                                                        cies. Generally, these problems relate to multiple-use con-
                                                                                   flicts, aesthetics, navigation, and environmental concerns,
                                                                                   all affecting the premit process.
                                                                                   Lantern and/or pearl nets Several operations in Washing-
                   Humboldt Bay                     Eureka                         ton and British Columbia utilize these types of hanging nets
                                                                                   on long lines or rafts to grow oysters for the half-shell trade.
                                                    California                     Trays Plastic netting is used in many areas along the west
                                                                                   coast for the production of single Pacific oysters and other
                                                                                   species for the commercial half-shell market. The method
                   Tomales Bay                                                     of using Vexar plastic netting was adapted from the French
                   Drakes Bay ( Estero)                    San Francisco           technique whereby sheets of material are folded over and
                                                                                   sewn to make a basket. These baskets or trays are laid on
                                                                                   a special metal or wood frame (rack) on the intertidal bed.
                                                                                   One of the major operations using this technique is in Willapa
                                                                                   Bay, Washington, and several other areas along the Pacific
                   Morro Bay                                                       coast are running tests to determine their feasibility.


                                                                                   Remote setting for seed
                                         Figure 1
                           General area of Pacific oyster production.              In recent years Pacific coast hatcheries have become very
                                                                                   important to the oyster farmers. For many years, consistent
                 During the past 20 years, several methods of off-bottom           supply of seed oysters to maintain annual production was
               cultivation for Pacific oysters and other species have been         dependent upon supplies from Japan, especially during the
               initiated. Each are briefly described below.                        post-World War H years prior to the 1970s. As Pacific oyster
                                                                                   seed shipments from Japan declined, natural catches of seed
               Long line culture involves the establishment of a system on         became available from some locations along the west coast
               the intertidal beds where shell cultch material with seed is        (Pendrell Sound, British Columbia, and Hood Canal and
               strung between poles on heavy braided polypropylene rope.           Willapa Bay, Washington). Figure 2 summarizes in part the
               This is a growing-culture operation at present and occurs in        seed production for the state of Washington during the years
               Grays Harbor and Willapa Bay, Washington. Floating long-            194.7-85. As shown in this figure, most of the Pacific oyster
               line culture with buoys has been used in northern Puget Sound       seed from Japan remained in the state of Washington. Al-
               on a limited scale for hanging lantern and pearl nets for grow-     though natural-caught seed may be available in Hood Canal,
               ing oysters.                                                        it is not a dependable source of seed every year. For exam-
                                                                                   ple, the two bays in north Hood Canal (Quilcene and Dabob

                                                                              66









                                            C  100
                                            A                                                                              PACIFIC
                                            S  90                                                                          00ASr
                                            E                                                                              TOTALFROM
                                            S  80                                                                   1
                                                                                                                    0      JAPAN
                                            0  70                                                                          FCR
                                            F  60                                                                          WASHK13TCN
                                            S  50                                                                          FROM 46PAN
                                            E
                                                                                                                           NATURAL
                                            E  40
                                            D                                                                              CATCHFRCM
                                                                                                             A             HOODCANAL,
                                            x  30
                                                                                                                           WA
                                            1
                                            0  20                                                                          FFICM
                                            0                                                                              PATCHERY
                                            0  10                                                                          PFCDJOW
                                                                                                                           EYED-
                                                 0                                                                         LARVAE IN
                                                  45      50      55      60      65       70       75     80       85     WA(EST.)
                                                                                  YEAR

                                       I

                                                                                    Figure 2
                                       Production of seed oysters in Washington compared with Japanese seed shipments to the U.S. Pacific
                                                                                  coast, 1947-85.




             Bay) as a general rule will produce commercial quantities                   after 0-12 days in 5'C storage (Fig. 4), and was able to show
             of seed only six or seven years out of ten, a difficult situa-              that the Pacific oyster eyed larvae should not be stored at
             tion for the oysterman who depends on this seed source.                     5'C beyond 8 days for best larval settlement or survival.
               A new culture technique has been recently initiated on the
             west coast in which setting-size eyed Pacific oyster larvae
             can be purchased from private hatcheries by the oyster
             growers. The larvae can be kept alive for several days at                         40-
             5'C in a cooler and sent great distances by air. Thus, the
             oyster grower can have a tank built on the farm and eyed
             larvae ordered for settlement. Although this concept, referred                    35-
             to as remote setting, has been tried experimentally for more
                                                                                           W
             than 20 years, it did not become an economical and accepted                   Cn                                                       30 OC
             practice until 7-8 years ago. Presently two main hatcheries,                      30-
             one in Oregon and one in Washington, produce over ten                                                                     0            P 5  C
                                                                                           X
             billion eyed larvae annually to supply the needs of the west
             coast growers who use remote setting to obtain seed. This
                                                                                               25-
             process was well described by Jones and Jones (1983). As                      Z
                                                                                           W
             shown in Figure 2, there has been a dramatic increase of
                                                                                           W
             over 80,000 cases of seed produced from hatchery eyed                         a.  20-                                                  200C
             larvae in 1985 alone, and over 100,000 cases annually since                   Z
             then.                                                                         W
               In 1983 there were an estimated 18 oyster farmers build-                        15-                                                  15 OC
             ing their own tanks to catch Pacific oyster seed from
             hatchery-produced eyed larvae. Recent estimates show that                                                                              350C
             over 50 farmers from Alaska to California, including British                      10 J
             Columbia, are using remote setting to securing seed for their
             oyster operations.
                                                                                                       15         20        25        30          35
               The cost of eyed larvae ranges from 8 to 12 cents/thou-                                               SALINITY %o
             sand depending on the time of year and the hatchery. Early
             research by Henderson (1983) has shown the importance of
             temperature and salinity for eyed larval settlement (Fig. 3).                                            Figure 3
             As demonstrated in Figure 3, remote setting tanks should                    Cumulative mean percent larval Crassostrea gigas settlement at rive
                                                                                         temperature levels (15-35*C) and at rive salinities (15-35%). Points
             be about 30'C and 30 ppt, respectively, for optimum results.                of intersection indicate factor interaction at the given coordinates.
             Henderson also ran tests to determine the percent settlement                                      (From Henderson 1983)

                                                                                    67







                                                                                                L-Dope and algal slurry to facilitate the remote setting of
                                                                                                Pacific oyster.
                    >  60-
                    5;
                    ir
                    M
                    U)
                       40-                                                                      Stock development through
                    0
                    M                                                                           genetic manipulation
                    I.-
                    Z
                    W  20
                                                                                                According to Hershberger et al. (1984), two developments
                    0. 01                                                                       of Pacific oyster culture in the United States have made selec-
                    Z
                    <                                                                           tion and direct breeding both feasible and attractive. First,
                    W
                             0        2        4         a        8       to        12          a successful artificial spawning technique for the Pacific
                       too-                                                                     oyster and development of a procedure for larval rearing pro-
                                                                                                vide the means to exercise control over the entire life history.
                                                                                                Recently, results from more detailed studies of condition-
                    UW                                                                          ingand spawning procedures have identified several factors
                    _J                                                                          that can improve gamete quality (Lannan 980, Lannan et al.
                    <                                                                           1981), Muranaka and Lannan 1984) and, thus, predictable
                    >
                    0: 60-
                    4                                                                           larval production.
                                                                                                  Secondly, Hershberger et al. (1984) indicated the technol-
                    Z                                                                           ogy of seed production in commercial oyster hatcheries had
                    W  40-
                                                                                                developed to a point where their seed has become competitive
                    UJ
                    CL                                                                          (in terms of reliability and cost) with seed collected from
                    Z  20-                                                                      natural production. It has only been within the past five years
                    W
                    M                                                                           that hatchery-produced spat of Pacific oysters has been in
                       oJ                                                           I           demand by the oyster growers (Clark and Langmo 1979).
                                                                                    -1            A systematic selection and breeding program has been
                             1        2        4         6        a        10       12          conducted with the Pacific oyster at the University of Wash-
                                            DAYS IN 5*C STORAGE                                 ington for almost 15 years (Beattie et al. 1978, 1980; Perdue
                                               Figure 4                                         et al. 198 1; Hershberger et al. 1984). It was initiated during
                                                                                                the 1970s when there were major summer mortalities occur-
                 Mean percent larval Crassostrea gigas settlement after 0-12 days in 5'C        ring along the Pacific coast which necessitated a look at the
                 storage. Comparative mean spat survival after 90 days for each 48-hour
                 storage interval is displayed above. Vertical bars indicate standard error     possibility of breeding for a strain of oysters resistant to sum-
                                   of means. (From Henderson 1983)                              mer mortalities. Histological studies into the mortalities
                                                                                                revealed there was no identifiable pathogen that could be
                                                                                                clearly related to the oysters dying in specific bays during
                                                                                                the summer. Detailed studies revealed mortalities may be
                 This is basic background information, but the oyster farmer                    related to the gametogenic cycle and the physiological pro-
                 will need to determine the requirements of his own system                      cesses and stresses that take place during that time (Perdue
                 to obtain best success.                                                        et al. 198 1). Thus, several approaches were utilized during
                    Recent activities related to remote setting involves the use                the past 15 years at the University of Washington oyster
                 of the chemical L-3, 4-dehydroxyphenylalanine, commonly                        genetics program, focusing on three areas: 1 Survival dur-
                 referred to as L-Dopa, which is also sold by one hatchery                      ing summer mortality, 2 genetic determination of carbo-
                 selling the eyed larvae. L-Dopa is used to facilitate larval                   hydrate (glycogen) content in relation to gametogenic cycles,
                 settlement in the farmers' tanks. As a general rule, one can                   and 3 the effects of inbreeding.
                 expect between 20% and 30% of the eyed larvae to meta-                           During the past four years a new focus has been added-
                 morphose and settle successfully. Discussions with several                     the development of a triploid oyster. This was pursued
                 oyster farmers reveal that a higher percentage is regularly                    because of the need by oystermen for a summer oyster that
                 achieved.                                                                      does not go through ftill gametogenesis. During the summer
                    After the larvae have settled, it is possible to feed them                  months a normal diploid oyster will produce eggs or sperm
                 for a day or two before they are taken from settling tanks                     and become milky. Although edible, the product is aesthet-
                 to the outside environment. Hatcheries also sell a concen-                     ically undesirable and in some cases unacceptable as a
                 trated algal paste or algal slurry (Krantz et al. 1982). The                   half'-shell oyster. Thus triploidy has been looked upon as a
                 algal cultures, usually made up of Tahitian Isochrysis or 3H                   potential for eliminating or reducing the incidence of gonadal
                 (7halassiosira), are grown in large tanks and passed through                   maturation in oysters, affectively neutering them for the fresh
                 a mechanical centrifuge for concentration into a paste. Thus,                  oyster trade during the summer.
                 the hatchery selling the eyed larvae can include sales of


                                                                                           68







            Summer mortality
                                                                                                               Adult
            Although summer mortality has abated in recent years, the                   Select brood stock     oysters       challenge.
                                                                                        (based on perfornionce                            %vith or
            approach utilized to study the problem and the breeding                          of sibs)
            program that evolved to attain resistant stocks are worth
            reviewing. A major part of the early work on this problem                                         Progeny
            focused on identification of the agent responsible for mor-                                       testing                   Mortality
            tality (Glude 1975). Studies in Japan concluded that the                                                                      t
            summer mortalities were largely the result of physiological
            stress associated with highly eutrophic conditions (Kogane-
            zawa 1975). In both Japan and the United States, mortalities                      Sib- adults                     Surviving
                                                                                              (yearlings)                       adults
            were generally associated with areas of high productivity,                             N* N@-@                    Condition
            high nutrient level, and water temperatures exceeding 200C,                                                         spa
                                                                                                  Gro-'t%h                  /.n d   n
                                                                                      Ancly@e genetic
            coincident with a period of maximum gonad maturation (Per-                 variability              Progeny
                                                                                      (electrophoretic         (seedfr in
            due et al. 1981). Laboratory research demonstrated that mass              analysis)              survivor x survivor)
            mortality approximating the characteristics of the natural                                         9     Cr
            situation could be induced by holding oysters in 20'C water
            and increasing the nutrient levels (Lipovsky and Chew 1972).                                     Figure 5
            Although studies by Grischkowsky and Liston (1974) dem-               Diagram of selection design and genetic analysis used in breeding oysters
            onstrated that Vibrio sp. may play a significant role in the          for resistance to mortality during simulated summer stress (from Beattie
            laboratory mortality tests, they do not appear to be a causative                   et al. 1978 and Hershberger et al. 1984).
            pathogen under field conditions.
              It should be noted that none of the early work in Japan
            on summer mortality included selective breeding as a method
            to mitigate the severity of this problem. One has to recognize          Although laboratory tests proved that resistant strains can
            that the initial information needed before conducting a selec-        be developed, it was necessary to field-test the various
            tion and breeding program is to determine whether the                 families in areas of known summer mortalities. It was dur-
            organism contains adequate genetic variability on which to            ing this period, the mid-1970s, that the summer mortalities
            base the program; thus, genetic variability tests through elec-       abated. However, we were able to determine that, although
            trophoretic analysis were conducted by Buroker et al. (1975).         increased gonadal development was not directly related to
            Their study indicated a good selective breeding potential and         high or low mortality, the timing of the mortality coincided
            led to a selection design and genetic analysis (Fig. 5) used          with maximum gonad development (Perdue et al. 198 1). Fur-
            in breeding oysters for resistance to mortality during sim-           ther, from testing the families when mortalities were still
            ulated summertime stress (Lipovsky and Chew 1972) to                  occurring, it was discovered that those with higher survival
            induce a 60-70% mortality. Survivors were spawned and                 had consistently higher carbohydrate (glycogen) stored
            mated by crossing a single male with a single female to               energy reserves than oyster families with lower survival.
            produce experimental families. Progress in increasing                 With this type of information, selected families with higher
            resistance in the families produced was measured by chal-             glycogen levels as well as better shell growth were bred in
            lenging offspring when they reached adulthood with the same           the hopes of developing an oyster with higher marketability.
            elevated temperature conditions. Results from selected
            groups were compared with those using an unselected and               Carbohydrate content
            control population to assess progress.                                Carbohydrate (glycogen) is the major stored energy reserve
              According to Hershberger et al. (1984), progeny from the            in oysters and during anaerobiosis is the only substrate
            initial crosses performed in 1973 and 1975 indicated a good           utilized for metabolic processes (Hochachka and Somero
            potential for development of oyster strains resistant to ther-        1973). In addition, it was pointed out by Gabbott (1975) that
            mal stress (Beattie et al. 1978). Out of the seven families           gamete production occurs at the expense of stored glycogen
            originally tested, two consistently survived the thermal stress       reserves. This is the primary reason glycogen levels have
            significantly better than the control groups and none of the          been shown to be inversely related to gonadal development
            selected families showed poorer survival. Thus, it appeared           in Pacific oysters (Matsumoto et al. 1934, Mann 1979,
            that selection could be used to improve resistance to one fac-        Hershberger et al. 1984). Perdue et al. (1982) and Hersh-
            tor involved with summer mortality, thermal stress.                   berger et al. (1984) indicated that heightened gonadal devel-
                                                                                  opment has a major influence on susceptibility to summer
                                                                                  stress conditions and that carbohydrate content may be a more
                                                                                  precisely measured trait on which to base selection. Further,
                                                                                  carbohydrate content is an important component of oyster
                                                                                  marketability. Immature or nonspawning (high glycogen con-
                                                                                  tent) oysters have a high market desirability compared with

                                                                              69







                                                                                              Triploidy
                      FAMILY A        FAMILY 8          FAMILY C           FAMILY 0
                                          Cr.,                                 -14            Recent work by two researchers, Standish K. Allen and
                                                                                              Sandra L. Downing at the School of Fisheries of the
                                                                                              University of Washington, has shown conclusively that
                                                                                              triploid Pacific oysters can be produced as a viable commer-
                                                                                              cial option (Allen 1986, Allen and Downing 1986, Down-
                                               Figure 6                                       ing and Allen 1987). Allen (1986) indicates that triploidy
                  Rotational line-breeding plan which produces eight full-sib and four        has been produced in shellfish using three different methods:
                            half-sib fandlies (from Hershberger et al. 1984).                 Chemical, pressure, and thermal induction. All three affect
                                                                                              inhibition of polar body development resulting in an addi-
                                                                                              tional maternal set of chromosomes. Allen pointed out that
                                                                                              all methods to induce triploidy depend upon absolute con-
                  mature oysters during peak gonadal maturation (low glycogen                 trol of the moment of fertilization and subsequent meiotic
                  content). Thus, selection and breeding to maintain high car-                events in the egg. Since the rate of these events is tem-
                  bohydrate content could also improve the marketability of                   perature-dependent, reproducibility of induction procedures
                  oysters (Hershberger et al. 1984). Over a ten-year period                   in a given species will depend on maintaining constant
                  the breeding program has provided lines with significantly                  temperature during incubation. Studies by Downing and
                  elevated carbohydrate levels, and are currently utilized for                Allen (1987) clearly demonstrate the dependence of tem-
                  broodstock for one company's production of gourmet oysters.                 perature on time in which treatment can take place. In their
                  Preliminary results on the carbohydrate content of a series                 studies they use primarily Cytochalasin B (CB) to induce
                  of selected families grown in different locations suggest there             triploidy. Although earlier work with hydrostatic pressure
                  is a major genetic component in the utilization of a glycogen               has been shown to produce triploidy in Pacific oysters
                  during gonadal development.                                                 (Chaiton and Allen 1985), the results were not as good as
                                                                                              with CB.
                  Inbreeding                                                                    ]Researchers Allen and Downing report that treatment
                  Hershberger et al. (1984) discussed the effects of inbreed-                 consists of adding I ing of CB dissolved in 1 ml, of
                  ing in the University of Washington selection and breeding                  dimethylsulfoxide (DMSO) to a liter of sea water contain-
                  program for oysters. They chose to avoid inbreeding depres-                 ing fertilized eggs at the beginning of any treatment. After
                  sion by the use of a scheme of rotational line crossing, a                  15 minues, the eggs are filtered through a 25-Mm screen and
                  systematic breeding design that minimizes the increase in                   then resuspending the zygotes in a 0. 1 % DMSO bath for
                  level of inbreeding per generation (Fig. 6). In this rotational             another 15 minutes. During this time, egg suspensions are
                                                                                              stirred occasionally during the treatment and rinsed. After
                  design (produces eight full-sib and four half-sib families) the             rinsing, zygotes are placed in appropriate tanks and reared
                  increase in inbreeding coefficient is less than 0.01 per genera-            according to accepted procedures (Breese and Malouf 1975).
                  tion. Although this approach does not decrease the amount                   Studies by Downing and Allen (1987) demonstrate con-
                  of inbreeding initially imposed by a small breeding popula-                 clusively that the time and temperature of treatment applica-
                  tion size, it does minimize the change across generations.                  tion are very critical (Fig. 7). Each of the Roman numerals
                  It should be noted that recent preliminary results from some                in this figure represents 15-minute intervals after fertiliza-
                  of the family bred for high glycogen levels (Beattie et al.                 tion of the eggs and the time at which each individual test
                  1986) suggest inbreeding depression by exhibiting poorer                    on different lots were made. The fitted curves reveal that
                  shell growth. This is presently being addressed in our                      the triploid induction maxima at 18', 20', and 25*C were
                  breeding studies, and the success from using this breeding                  52, 76, and 90%, respectively. Also, lowering the tem-
                  design is still being assessed.                                             perature delays the induction peaks; maxima at 25', 20',
                                                                                              and 18'C are approximately 30, 45, and 50 minutes post-
                                                                                              fertilization, respectively. Two private hatcheries are now
                                                                                              utilizing these techniques to produce triploidy Pacific oysters,
                                                                                              and both have them already available for the half-shell oyster
                                                                                              market, especially for the summer periods. Further, there
                                                                                              are now available a hatchery manual and accompanying video
                                                                                              by Allen et al. (1989) for producing triploidy oysters.








                                                                                        70






                                                                                           Concluding statement
                    100  18-@                                                              An attempt has been made to briefly summarize the recent
                    80   -                           P =.41 (T) 1. 67e -(.034)T            changes in oyster cultivation along the west coast of North
                    60-                                               r 2=.631             America. Although intertidal bed cultivation is still the most
                                                                                           important, attempts have been made to implement a variety
                    40                                                                     of off-bottom culture techniques in many select areas. Off-
                                                                                           bottom culture is growing, but continues to encounter diffi-
                    20                                                                     culty because of permit application requirements related to
                       0                                                                   the sociopolitical climate existing in most populated areas
                    100                                                                    in the United States. This is especially true for applications
                         20 OC        0                                                    for raft or floating type culture facilities.
                    so-                                          2.90    (@62)`r              There is no doubt that the new concept of remote setting
                                0                     P   02 M       e-
                                                   0                                       of eyed larvae for Pacific oysters will grow. Less than 10
                    60-         0     0            0                  r2=.930              years ago the oyster farmer on the west coast still needed
                q,  40                                                                     to be concerned with getting adequate supplies of seed
                                                               0                           oysters. Now the natural catches in several areas, comple-
                    20-                                                                    mented by many farmers building setting tanks on their own
                      0                                                                    property to catch their own seed through remote setting, have
                    100                                                                    removed this concern. In essence, some growers no longer
                         25*C)L-.@                                                         depend on natural catches because of remote setting for their
                    80-       1 /1A                   P=.77(T)2-o'e    -(.069)T            own seed. The cost is equivalent according to some growers.
                    60-      1        A                                r2=764                 Two hatcheries, Coast Oyster Hatchery in Washington and
                            II                                                             Whiskey Creek Hatchery in Oregon, were expected to pro-
                    40- 1   ,                      A                                       duce over 12 billion eyed larvae for sales or for their own
                                             A                                             use in 1986 to satisfy the needs of the west coast industry.
                    20-                                                                    There are other hatcheries in California and British Colum-
                      Of                                                                   bia, and one being proposed for Alaska.
                          I     I[    M     IZ Y M ME M                     IX                Stock development through genetics and breeding studies
                                         Treatment periods                                 have been in existence on the west coast for more than 10
                                                                                           years. The University of Washington School of Fisheries has
                                           Figure 7                                        been investigating summer mortalities of Pacific oysters in
             Induction proffles at 18*C (top), 20'C (middle), and 25*C (bottom) were       the late 1960s and early 1970s and attempting to breed a resis-
             produced by ritting curves to data using multiple linear regression.          tant stock to this disease. No known pathogen was found con-
             Derived equations and correlation coefficients are shown. Points repre-       sistently related to this summer kill. Further, studies strongly
             sent percent triploidy in each treatment group. Treatment periods are         suggested that the phenomenon was related to physiological
             15-min intervals beginning at fertilization. (Downing and Allen 19n           stress related to the reproductive cycle. Stocks of oysters that
                                                                                           died generally had lower carbohydrate (glycogen) levels.
                                                                                           With this in mind, a breeding program was established to
                                                                                           develop stocks with higher glycogen levels and including
                                                                                           an approach to minimize inbreeding problems. Although
                                                                                           attempts were made to reduce this problem, early results
                                                                                           show continued breeding of summer oysters for high glyco-
                                                                                           gen can also lead to oysters with slow shell growth. This
                                                                                           problem is presently being addressed at our experimental
                                                                                           hatchery.
                                                                                              The production of triploid Pacific oysters is looked upon
                                                                                           very favorably by the shellfish growers on the west coast
                                                                                           of North America. Researchers at the University of Wash-
                                                                                           ington School of Fisheries have been instrumental in the
                                                                                           development of the triploid oyster. The fact that these triploid
                                                                                           oysters have minimal gametogenesis as compared with
                                                                                           normal diploid oysters and, thus, more carbohydrates in the
                                                                                           tissues during summer, ensures that these neutered oysters
                                                                                           will be in great demand for the half-shell oyster trade dur-
                                                                                           ing the summer months.


                                                                                      71







                    Citations                                                                           Hershberger, W.K., J.A. Perdue, and, J.H. Beattie
                                                                                                             '1984 Genetic selection and systematic breeding       in Pacific oyster
                    Allen, S.K., Jr.                                                                           culture. Aquaculture 39:237-246.
                          1986 Genetic manipulations. Critical review of methods and perfor-            Hochachka, P.W., and G.N. Somero
                          mances, shellfish. Paper presented at EIFAC/FAO Symposium on                       @1973 Strategies of biochemical adaptation. W.B. Saunders Co.,
                          Selection, Hybridization and Genetic Engineering in Aquaculture of                   Phila., 358 p.
                          Fish and Shellfish for Consumption and Stocking, Bordeaux, France,            Jones, G., and B. Jones
                          May 27-30, 1987, 38 p. Rutgers Univ. Shellfish Res. Lab., Pt.                      1983 Methods for setting hatchery produced oyster larvae. Inf. rep.
                          Norris, NJ 08349.                                                                    4, Mar. Resourc. Br., Min. Environ., Prov. Brit. Col., 94 p.
                    Allen, S.K., Jr., and S.L. Downing                                                  Koganezawa, A.
                          1986 Performance of triploid Pacific oysters. Crassostrea gigas                    1975 Present status of studies on the mass mortality of cultural oysters
                          (Thenberg). I. Survival, growth, glycogen content, and sexual matura-                in Japan and its prevention. In Proc. Third U.S. /Japan Meeting on
                          tion in yearlings. J. Exp. Mar. Biol. Ecol. 102:1-12.                                Aquaculture, Tokyo, Oct. 1974, p. 29-34. Spec. publ., Jpn. Fish.
                    Allen, S.K., Jr., S.L. Downing, and K.K. Chew                                              Agency and Jpn. Sea Reg. Fish. Res. Lab.
                          1989 Hatchery manual for producing triploid oysters. WSG 89-3,                Krantz, G.E., G.J. Baptist, and P. W. Meritt
                          Wash. Sea Grant, Univ. Wash., Seattle, 27 p.                                       1982 Three innovative techniques that made Maryland oyster hatchery
                    Beattie, J.H., W.K. Hershherger, K.K. Chew, C. Malinken, E.F.                              cost effective. Presented at the 74th Annu. Meet. Nad. Shellfish.
                     Prentice, and C. Jones                                                                    Assoc., Baltimore, MD, June 1982. MD Dep. Nat. Resourc., An-
                          1978 Breeding for resistance to summertime mortality in the Pacific                  napolis 21401.
                          oyster (Crassostrea gigas). Wash. Sea Grant Prog. Rep. WSG 78-3,              Lannan, J.E.
                          13 p.                                                                              1980 Broodstock management of Crassostrea gigas: 1. Genetic varia-
                    Beattie, J.H., K.K. Chew, and W.K. Hershberger                                             tion in survival in the larval rearing system. Aquaculture 21:
                          1980 Differential survival of selected strains of Pacific oysters                    323-336.
                          (Crassostrea gigas) during summer mortality. Proc. Nail. Shellfish.           Larman, J.E., A. Robinson, and W.P. Breese
                          Assoc. 70:184-189.                                                                 1980 Broodstock management of Crassostrea gigas. H. Broodstock
                    Beattie, J.H., J.A. Perdue, W.K. Hershberger, and K.K. Chew                                conditioning to maximize larval survival. Aquaculture 21:337-345.
                          1986 Effects of inbreeding and growth in the Pacific oyster during            Lipovsky, V.P., and K.K. Chew
                          summer mortality. Proc. Nail. Shellfish. Assoc. 70:184-189.                        1972 Mortality of Pacific oyster (Crassostrea gigas): The influence
                    Breese, W.P., and R.E. Malouf                                                              of temperature and enriched seawater on survival. Proc. Natl.
                          1975 Hatchery manual for Pacific oyster. Oreg. State Univ. Sea                       Shellfish. Assoc. 62:72-82.
                          Grant Prog. Rep. ORESU-H-75-002, 23 p.                                        Mann, R.
                          1977 Hatchery rearing techniques for the oyster Crassostrea rivularis.             1979 Some biochemical and physiological aspects of growth and
                          Gould. Aquaculture 12:123-126.                                                       gametogenesis in Crassostrea gigas and Ostrea edulis grown at sus-
                    Buroker, N.E., W.K. Hershberger, and K. K. Chew                                            tained elevated temperatures. J. Mar. Biol. Assoc. U.K. 58:95-110.
                          1975 Genetic variation in the Pacific oyster, Crassostrea gigas. J.           Matsumoto, B., M. Matsumoto, and M. Hibino
                          Fish Res. Board Can. 32:2471-2477.                                                 1934 Biochemical studies of Magaki (Ostrea gigas). H. The seasonal
                    Chaiton, J.A., and S.K. Allen                                                              variation in the chemical composition of Ostrea gigas Thunberg.
                          1985 Early detection of triploidy in the larvae of the Pacific oyster,               J. Sci. Hiroshima Univ. A4:47-56.
                          Crassostrea gigas, by flow cytometry. Aquaculture 48:35-43.                   Muranaka, M.S., and J.E. Lannan
                    Chew, K.K.                                                                               1984 Broodstock management of Crassostrea gigas: Environmental
                          1984 Recent advances in the cultivation of molluscs in the Pacific                   influences on broodstock conditioning. Aquaculture 39:217-218.
                          United States and Canada. Aquaculture 39:69-81.                               Perdue, J.A., J.H. Beattie, and K.K. Chew
                    Clark, J.E., and R.D. Langino                                                            1981 Some relationships between gametogenic cycle and summer
                          1979 Oyster seed hatcheries on the U.S. west coast:    An overview.                  mortality phenomenon in the Pacific oyster (Crassostrea gigas) in
                          Mar. Fish. Rev. 41(12):10-16.                                                        Washington State. J. Shellfish. Res. 1:9-16.
                    Downing, D.L., and S.K. Allen, Jr.
                          1987 Optimum treatment parameters for induction of triploidy in
                          Pacific oyster, Crassostrea gigas, using cytochalasin B. Aquaculture
                          63:1-21.
                    Gabbott, P.A.
                          1975 Storage cycles in marine bivalve molluscs: A hypothesis con-
                          cerning the relationship between glycogen metabolism and gameto-
                          genesis. In Barnes, H. (ed.), Proc. 9th Eur. Mar. Biol. Symp., p.
                          198-211. Aberdeen Univ. Press.
                    Glude, J.B.
                          1975 A summary report of Pacific oyster mortality investigations
                          1965-1972. In Proc. Third U.S./Japan Meeting on Aquaculture,
                          Tokyo, Oct. 1974, p. 1-28. Spec. publ., Jpn. Fish. Agency and
                          Jpn. Sea Reg. Fish Res. Lab.
                    Grischkowsky, R.S., and I Liston
                          1974 Bacterial pathogenicity in laboratory-induced mortality of the
                          Pacific oyster (Crassostrea gigas, Thunberg). Proc. Nail. Shellfish.
                          Assoc. 64:82-91.
                    Henderson, B.A.
                          1983 Handling and remote setting techniques for Pacific oyster larvae.
                          M.S. thesis, Oregon State Univ., Corvallis, 37 p.



                                                                                                 72






            A Physiological Approach                                                     Since the introduction of the rotifer Brachionus plicatilis to
                                                                                         the seedling culture as a food organism about 25 years ago
            to Problems of Alass                                                         (Ito 1960), mass-culture techniques for marine fish fry have
                                                                                         progressed so remarkably that, for instance, two kinds of
            Culture of the Rotifer                                                       fish can be produced in numbers exceeding 10 million per
                                                                                         year (1984) as seedlings for mariculture and for releasing
                                                                                         to the coastal waters (red sea bream, 39.3 million; flat fish,
                                                                                         13.7 million). Feeding schedules of seedlings were classi-
            KAZUTSUGU HIRAYAMA                                                           fied into four types according to size of larvae or type of
            Faculty of Fisheries                                                         required foods (Fig. 1) (Kitajima 1985). The only fish seed-
            Nagasaki University                                                          lings that can be produced on a mass-production scale are
            Bunky-o-machi, Nagasaki, 852 Japan                                           the standard type or the bottomfish type which can utilize
                                                                                         the rotifer as the major food throughout their larval stage.
                                                                                         This fact emphasizes the importance of the rotifer as a food
                                                                                         organism.
            ABSTRACT                                                                        Table I shows examples      'of red sea bream, Pagrus major,
                                                                                         production in typical hatcheries in Japan. An average hatch-
            The introduction of the rotifer Brachionus plicatilis as a food              ery can produce more than 1 million young (>10 min total
            organism in 1960 has made such remarkable progress in the                    length) per year. However, as shown in Table 1, compared
            mass-culture techniques of marine fish fry that, for instance,               with the tank volume needed for culturing fry, a much larger
            about 40 million red seabream young were produced in Japan                   tank volume is needed for rotifer production and an even
            in 1984. Strains of rotifer used in Japanese hatcheries are                  larger volume for marine Chlorella culture. There have been
            roughly divided into two groups: L type and S type, according
            to differences in morphology and in growth response to envi-                 many attempts to develop artificial food for fry, and some
            ronmental temperature. The rotifer has high food selectivity.                of them are already being produced on a commercial scale.
            Whereas living materials are usually acceptable, nonliving                   However, these cannot completely replace the rotifer but only
            materials are rejected by the rotifer, although there are many               function in a supplementary role. Therefore, the rotifer is
            exceptions. Greater attention to food selectivity is needed when             and will remain the main food for fry production during the
            attempting to develop new kinds of food.                                     next decade. Government officials project that the demand
              The dietary value of several kinds of phytoplankton were com-              for young red sea bream for release and mariculture will
            pared with marine Chlorella by conducting parallel tests under               reach 50 million or more in 1987 (Aihara 1984). Twice the
            bacteria-free conditions. Green or blue-green algae were found               present rotifer production will be required for the release
            to be excellent food, while diatoms had a low dietary value. The             of artificially produced fish fry into coastal waters to effec-
            nutritive value of baker's yeast was found to be extremely low               tively increase coastal resources and to supply enough fry
            when tested under bacteria-free conditions with pure washed
            yeast cells. Therefore, the success of mass culture of the rotifer           for mariculture.
            fed only yeast is due to byproducts of decomposition or to the
            growth of phytoplankton or bacteria in culture tanks which
            become a supplementary source of the nutrient lacking in yeast,
            such as vitamin B1.2.                                                                          Larval stage            Juvenile stage
              The rotifer requires fat-soluble vitamins A, D, and E as essen-
            tial nutrients. The rotifer can tolerate relatively low oxygen level.           Standard tyN
                                                                                                                                        ...................
            Low oxygen concentration is apparently suitable to rotifers fed                                                                 . . .... ...
            with yeast because the bacteria which produces vitamin B12 in                   Carnivorous        I F1
            culture tanks usually belongs to facultative anaerobic bacteria.                       type
              Un-ionized ammonia accumulating in culture tanks is prob-
            ably one of the causes of suppressed growth of the rotifer. Also                Bottom fish
                                                                                                   type              ES t@_
                                                                                                                                     L.J I--
            pH may have an indirect rather than a direct effect on rotifer
            growth through un-ionized ammonia.                                              Small fish
                                                                                                    type

                                                                                                                         U

                                                                                                              Larvae of bivalves, 0
                                                                                                              Ultra tiny rotifer 9         Small copepods
                                                                                                              Rotiller                     Minced,or
                                                                                                                                            formu ated food



                                                                                                                      Figure 1
                                                                                         Four types of feeding schedules for larval and juvenile stages of many
                                                                                                                 useful marine fishes.


                                                                                    73









                                                                                                       Table 1
                                                             Seedling production of red sea bream in typical sea-farming centers in Japan.

                                                                        A                         B                            C
                                                                                                                                                        Tank volume              Tank volume
                                                                    Number                        Tank                    Number of                        used for                 used for
                                                                    produced                    volume                 rotifers  supplied                   rotifers               Chlorella
                        Hatchery            Year             (X 101)            (A/B)             (fro)            (:K 104)               (C/A)               (m  3)                  (rro)

                            1               1981             1043.7             (5@8)             180              4,111,000              (3.9)               1200                    2400
                            1               1982             3126.0             (9@9)             315              25,377,000             (8.1)               1200                    2400
                            1               1983             3033.0            (11.2)             270              18,337,000             (6.0)               1200                    2400
                            H               1983             3240.0             (6.2)             520              30,832,000             (9.5)                 672                   2170
                           Hl               1983             2780.0             (2.8)             1000             19,670,000             (7.0)                 313                   1430

                        1 Hiroshima Prefectural Sea-Farming Center; H           Hakatajima National Sea-Fanning Center; III Kamiura National Sea-Fanning Center






                                                                                                       Table 2
                                                                                    Characteristics of two strains of rotifer.


                                                                                                          Lorica                          Water temperature ('C)

                                                                                            Length                 Shape                                  Lower limit
                                                 Type                                          Ym             (anterior spine)            Suitable         for growth

                                                S (B.  plicatilis rotundiformis)           150-220                 Round                  28-35                 20
                                                                                                                   (pointed)
                                                L (B.  plicatilis typicus)                 200-360                 Slender                18-25                  10
                                                                                                             (obtuse angled)





                        This paper presents a physiological approach to present                                    as well as morphological variation in the electrophoretic
                     problems in improving mass culture techniques of the rotifer.                                 pattern (Serra and Miracle 1983, 1985; Snell and Carrillo
                                                                                                                   19:84; Snell and Winkler 1984). Therefore, we should study
                                                                                                                   genetic differences between the two types by electrophoretic
                     Rotifer variations                                                                            procedures. These studies may add fundamental knowledge
                                                                                                                   toefforts to develop very small or very large strains by selec-
                     After introduction of the rotifer into mass production of fry,                                tion or hybridization, strains suitable for rearing small- or
                     early studies on the physiological responses of rotifers to                                   large-mouthed fry.
                     environmental conditions ignored variations between strains.
                     However, recently the existence of great variations among
                     rotifers has become recognized. In Japan, strains of rotifers                                 Search for suitable food
                     used in hatcheries were roughly divided into two groups-
                     L type and S type-according to size and shape of the lorica                                   The food material usually used in rotifer mass culture is
                     and shape of the spines of the anterior lorica (Fukusho 1983).                                marine Chlorella. However, recent investigations have re-
                     The two strains also have different growth responses to                                       vealed that some phytoplankton used as Chlorella in Japa-
                     enviromnental temperature. Table 2 summarized the mor-                                        nese hatcheries belong to the family Eustigmatophyceae,
                     phological and physiological differences between L and S                                      genus Nannochloropsis (Maruyama et al. 1986). As men-
                     types. S-type rotifers are suitable for rearing of small-                                     tioned above, production of Chlorella requires a huge tank
                     mouthed larvae such as groupers and rabbit fishes. On the                                     volume and sometimes the supply is unstable. Therefore,
                     other hand, L-type rotifers are best for large-mouthed larvae.                                efforts have been undertaken to find suitable food material
                     Recent studies have shown that the S and L types should be                                    to replace Chlorella. One approach is to culture the rotifer
                     divided into different genetic strains and classified tax-                                    with the objective food on a mass-culture scale. Tetraselmis
                     onomically as subspecies B. plicatilis typicus and B. plicatilis                              tetrathele has been introduced as a good suitable food algae
                     rotundifonnis, respectively (Suzuki 1983). Studies outside                                    (Okauchi and Fukusho 1984). Baker's yeast and marine yeast
                     Japan reported the varieties in B. plicatilis that show genetic                               have been practically utilized (Hirata and Mori 1967,

                                                                                                          74








                                                                                                       Table 3
                                                                            Filter feeding of the rotifer Brachionus plicatilis.


                                                                                              Water
                                                              Density                      temperature               Filtration rate
                   Food                                      (cells/mL)                       CC)                      (,ul/h/ind.)                Reference

                   Dunaliella salina                     (5.0-14.4) x 104                  20                          0.64-1.5                    Doohan 1973
                   Synechocaccus sp.                                8 x  106               26.1-28.1                          3.0                  Ito in Doohan 1973
                   Chlorella sp.                                 213 x 104                 25                              4-6                     Hirayama and Ogawa 1972
                   Chiamydomonas sp.                               lox 10,                 23                                 9.4                  Chotiyaputta and Hirayama 1978
                   Olisthodiscus sp.                                5 x 10'                23                                 2.0                  Chotiyaputta and Hirayama 1978
                   Protozoa                                      1.75 x 10'                25                                 8.1                  Hino et al. 1981a
                   Bacteria                                      1.91 x lo'                25                                 3.4                  Hino et al - 198 1 a
                   Dunaliella tertiolecta                        1.03 x IW                    ?                              10                    Deway in Starkweather and Gilbert 1977
                   Activated sludge                                                        25                          0.33-5.45                   Hino and Hirano 1980





                                                                                                       Table 4
                                                             Frequency (movement/min) of mastax movement of rotifers after feeding.

                                                       Chlamydornonas sp.                                                  Food                                                   Seawater

                   Food                                Avg.                 SD                t test             Avg.                 SD                t test              Avg.                SD

                   Baker's yeast                       68.0                 23.6                                 62.9                 23.4                                  22.1                11.6
                   Pavlova lutheri                     65.5                 34.3                                 74.0                 31.2                                  33.3                20.0
                   Cyclotella cryptica                 44.6                 27.8                                 53.2                 27.7                                  11.4                10.5
                   Gluten                              66.1                 22.4                                 58.1                 15.7                                  26.0                16.3
                   Egg albumin                         70.1                 30.2                                 54.5                 15.7                                  31.5                17.5
                   Milk                                66.1                 22.4                                 51.2                 21.3                                  29.0                16.3
                   Corn starch                         78.1                 21.2                                 60.4                 15.8                                  24.4                17.1
                   Olisthodiscus    sp.                58.8                 26.5                                 25.7                 15.7                                  20.6                11.2
                   Linoleic: acid                      79.6                 25.4                                 32.0                 12.1                                  34.4                16.7
                   Oleic acid                          79.6                 25.4                                 20.0                 16.6                                  34.4                16.7
                   Culture medium                      70.1                 30.2                                 39.5                 13.4                                  31.5                17.5

                   *Significant at 5%; **significant at       I%; ***significant at 0. 1%.




                 Furukawa and Hidaka 1973). Bacterial flocs (Yasuda and                                         food selection, as explained with B. cariciflores (Gilbert and
                 Taga 1980), photosynthetic bacteria (Sakamoto and                                              Starkweather 1977). Therefore, after feeding various kinds
                 Hirayama 1983), activated sludge (Hino et al. 198 la, b), dry                                  of food particles, the frequency of mastax movement may
                 Chlorella (Hirayama and Nakamura 1976), concentrated                                           reflect food selectivity. Table 4 presents frequencies of mas-
                 Chlorella, and AMT flocs (Fukuhara et al. 1982, Higashihara                                    tax movement after feeding many kinds of food particles,
                 et al. 1983) have been examined. AMT is the residue of                                         together with frequency data of the same individuals fed the
                 distillation of alcohol produced by fermentation of molasses.                                  preferred Chlamydomonas sp. and, as controls, only filtered
                 AMT floc means microbial flocs produced from AMT plus                                          seawater containing no food particles (Funamoto and Hira-
                 potassium phosphate with strong aeration. Formulated food                                      yama 1982). Differences between frequencies for each food
                 for the rotifer is now under development (Gatesoupe and                                        and for controls appear to be due to food selectivity. Many
                 Luquet 1981; Gatesoupe and Robin 1981, 1982).                                                  living materials are acceptable to the rotifer, while nonliving
                    Another approach is to investigate the physiological                                        materials are rejected, although there are many exceptions.
                 response of the rotifer to food, such as food selectivity and                                  We must pay more attention to food selectivity as we attempt
                 nutritional requirements. Table 3 presents data on the filter-                                 to develop new kinds of food, because rejected food causes
                 ing rates of rotifers obtained by using suspensions of many                                    severe problems by fouling the culture water, even if the
                 kinds of particles (Hirayama 1983). The broad distribution                                     nutritive value is complete for rotifer growth.
                 of data suggests that the rotifer is highly selective of food,
                 though strains employed in the experiments may differ. Food
                 particles that reach the mastax have passed three barriers for

                                                                                                          75







                       Culture methods
                                                                                                                                                           Relative r
                       In order to evaluate the nutritive effects of foods or sup-                                                                0                    0.  5                   1.0
                       plementary effects of nutrients added to the basic food sus-                                                         Synechococcus-                                    A
                       pension, batch culture and individual culture methods were                                                           eiongatus
                                                                                                                                            Chiamyclomonas-                    A
                       employed. When necessary, rotifers were cultured under                                                               SP*
                                                                                                                                            Pavlova-                       A
                       bacteria-free conditions. The simplest is the batch culture                                                          Wther.
                                                                                                                                            CiLinaliella-                    A
                       method in which offspring of the first-laid eggs hatched in                                                          tertiolecta
                                                                                                                                            cyclotella                       A A
                       one day are cultured in test tubes, each containing four or                                                          cryptica
                                                                                                                                            ELJtrePtieil0              A
                       five individuals with the specific food to be tested. During                                                         SP-
                                                                                                                                            NitzschiQ            A
                       cultivation, the culture water is not replaced and no addi-                                                          Tet Clostrium                                             A
                                                                                                                                            ra-Irl
                       tional food is added to the tubes. After several days of culture,                                                    Oro, Ise
                       the increase in the number of rotifers is determined and the                                                                        Relative Ro
                       effect on population growth evaluated by comparing the                                                                     0                    0.5                     1.0
                       change in numbers of individuals.                                                                                    S, nechococcus-
                          In individual culture, first-laid eggs are cultured separately                                                    Y
                       in many test tubes, each containing two individuals under                                                            Chlar"ydomonas-
                       defined conditions. These are observed daily with renewal                                                            Pavlova-
                       of food suspension, and the numbers of surviving individuals                                                         Dumliella-
                       and of eggs laid are counted. From daily survival rate and                                                           Cyclotella           0            0
                       fecundity data, two indices-net reproduction rate and in-                                                            Eutreptiella
                       trinsic rate of population growth-are estimated by Birch's                                                           Nitzschia
                       method (Birch 1948). The values of indices calculated repre-                                                         Tetraselmis
                       sent the growth phase of a group according to the fecundity
                       schedule obtained by the individual culture method. Net                                                                                 Figure 2
                       reproduction rate (Ro) is the number of eggs laid by an                                           Relative values (closed symbols) of two indices for each pbytoplankton
                       average female in her lifetime or the rate of multiplication                                      compared with dietary effect of marine Chlorella. Open symbols show
                       in one generation. Intrinsic rate of population increase (r)                                      relative values for Cycrotella cryptica calculated against those of
                       is the constant in the differential equation of population in-                                    DunaUella tenriolecta in a parallel experiment using the two species.
                       crease, dNIdt = rN, in an unlimited environment (N =
                       number of animals, t = days elapsed since beginning of test
                       tube culture).                                                                                                       280- 0 Yeast: 50,ug/m I
                         The advantage of evaluation by batch culture is that the                                                           .2 0 Yeast: 200,wg/mi
                       culture conducted through several generations makes the
                                                                                                                                            ,240-
                       influence of physiological condition during stock culture                                                            i@
                       negligible. However, the batch culture has its disadvantage                                                          200-
                       in terms of the difficulty in keeping the density of food sus-
                       pension constant.                                                                                                    160

                                                                                                                                            ed
                                                                                                                                            2120
                       Nutritional comparisons
                                                                                                                                            S80-
                       Several kinds of phytoplankton were compared with marine                                                             -
                       Chlorella for nutritional value by the parallel test of individual                                                   0
                                                                                                                                            40-
                                                                                                                                                                                            @t inoculation
                       cultures under bacteria-free conditions, using the first-laid                                                        E20
                       eggs derived from an actively growing group (Hirayama                                                                :z A'
                       et al. 1979). The nutritional value of each plankton was                                                             0005 Of           0.2      Q4      06       1.6
                       evaluated according to the ratios of r and Ro and compared                                                           Concentration     of vitamin B12 (,Wg/Ml)
                       with those obtained with Chlorella. The relative values of                                        L
                       many pbytoplankton shown in Figure 2 indicate that green                                                                               Figure 3
                       or blue-green algae are usually excellent food. Tetraselmis                                       Effect of supplementary vitamin B,2 on rotifer numbers in suspension
                       tetrathele, which was recently recommended for use as a food                                                         of baker's yeast in batch culture, 23'C.
                       for rotifer mass culture, possesses a higher nutritive value
                       for rotifer growth (Hirano and Hirayama 1984). The fact that
                       diatoms have a low nutritive value agrees with the observa-                                                          The nutritive value of baker's yeast was examined under
                       tion that the propagation of diatoms in mass-culture tanks                                        bacteria-free conditions. Tests by both methods for nutritive
                       sometimes suppresses growth of the rotifers.                                                      evaluation indicate a nutritive deficiency of the yeast (Fig. 3,
                                                                                                                         Table 5) (Hirayama and Funamoto 1983). The eggs laid are

                                                                                                                  76







              not viable, and the rotifers exhibited no growth. Addition                              although several kinds of food such as baker's yeast strength-
              of vitamin B12, however, can improve the nutritive value of                             ened with essential fatty acid (co yeast) contain little vitamin
              baker's yeast so that, along with the supplement of vitamin                             B12, the bodies of the rotifers grown successfully on such
              B12, it can support the growth of the rotifer. However, values                          diets contained high levels of vitamin B12 (Fig. 4) Imada
              of indices by two evaluation methods are still much lower                               1984).
              than those in marine Chlorella suspension. In spite of ex-                                In Kaiike, Kagoshima prefecture, photosynthetic bacteria
              tremely low nutritive value of baker's yeast, there are many                            growth supports feral rotifers as a main energy source (Mat-
              cases in which the successful mass culture of the rotifer was                           suyarna and Shirouzu 1978). After isolation of the bacteria,
              achieved by feeding only baker's yeast as a food source. The                            the nutritive value of such bacteria to rotifer growth was ex-
              nutritive test on the decomposed marine yeast, and on the                               amined. The photosynthetic bacteria could not support high
              addition of marine Chlorella at extremely low density to a                              growth of the rotifer, while an extremely low-level supple-
              marine yeast suspension, revealed that the success of mass                              ment of marine Chlorella was effective in strengthening the
              cultures of rotifers fed with baker's yeast alone may be im-                            nutritive value of this bacteria (Sakamoto and Hirayama
              proved by the byproducts of decomposition or by the growth                              1983).
              of phytoplankton or bacteria in the culture tanks (Hirayama                                As mentioned above, improvement of the nutritive defi-
              and Watanabe 1973). These provide a supplementary source                                ciency of baker's yeast by supplement of vitamin B12
              of the nutrients lacking in yeast, such as vitamin B12. These                           indicates that vitamin B12 is one of the essential nutritive
              supplementary effects are also supported by the fact that,                              elements to the rotifer as shown by Scott (1981). Nutritive
                                                                                                      requirements of the rotifer for fat-soluble vitamins were
                                                                                                      examined by means of supplying each of them to the basic
                                                  Table 5                                             food suspension of baker's yeast plus vitamin B12. The
                 Two indices obtained by individual culture of rotifers in suspensions                results by individual and batch cultures are shown in Figure
                 of baker's yeast (50 Mg/mL) supplemented with vitamin B,2 in                         5. Each addition of vitamins A, D, and E was effective on
                                    various concentrations at 23*C.                                   rotifer growth, and combinations of these vitamins are more
                 Concentration              Intrinsic rate of            Net reproduction             effective than addition of a single vitamin. These results in-
                 of vitarnin B12          population increase                   rate                  dicate that the three vitamins are essential nutritive elements
                    (,ug/mL)                        (r)                         (Ro)                  for growth of the rotifer (Satuito and Hirayama 1986).

                      0                           0.002                         0.70
                      0.01                        0.03                          1.20                  Environmental conditions regulating
                      0.05                        0.25                          3.78                  rotifer growth

                                                                                                      As mentioned above, the response of rotifer growth to tem-
                              0.5    0.6          6.6   5.3       11231    7258                       perature is different in S and L strains (Table 2). L-type
                          0.01    2.5     7.4      42-69 13803         6222 1363E.                    rotifers tolerate relatively lower temperatures; in contrast,
                                                                                                      S types are adjusted to relatively high temperatures (Ito et al.
                    @@00 -                                                                            1981). Although other physiological responses to environ-
                      90-                                                                             mental conditions may be reflected by strain differences,
                                                                                     -9000
                    .280.                                                            8=               there has been no study in which close attention was paid
                    a                                                                    U
                    :'70 -                                                           7000             to strain differences. On osmoregulation in the rotifer, it has
                      60-
                                                                                     -6000 o,         been shown that this species has a high ability to tolerate a
                                                                                     -5000 137
                                                                                                      wide range of external concentrations of salts, and that the
                    M40 -                                                            .4000M           lack of ability to regulate hyposmotically at concentrations
                    ,a                                                                   c:
                    c@ 30 -                                                          3000'E
                    03                                                                   a            approaching full-streno seawater suggests a marine ancestry
                    c 20-                                                            2000:@
                    E                                                                                 for this animal (Epp and Winston 1977). Observations in
                    210-                                                             1000
                    5                                                                                 mass-culture tanks showed that appropriate pH values for
                                    u
                                    .2                                                                mass culture of the rotifer ranged from 7.1 to 7.5 (marine
                             Z    _-_0
                                  c:
                                      CW                            CE
                                                        r                                             yeast) and 7. 5 to 9. 1 (baker's yeast) (Furukawa and Hidaka
                                                                                                      1973). However, Epp and Winston (1978) revealed by their
                                  Q: M    <       Co   2            CD  'a U    <_                    laboratory culture that a wide range of pH, from 6.5 to 8.5,
                              Filtrate (A)             Food (B)       Rotifer (C) J                   had no direct harmful effect on the rotifer population growth.
                                               AMT: Alcohol fermentation syrups                       Yu and Hirayama (1986) pointed out that un-ionized am-
                                                                                                      monia accumulating in the culture water could be one of the
                                                Figure 4                                              causes of sudden decrease or suppressed growth of the
              Contents of vitamin B12 in culture water, (A) filtrates of AW and                       rotifer, and that high pH value may not directly, but may
              AMT floc, (B) in several kinds of food for the rotifer, and (C) in the                  indirectly, influence rotifer growth through un-ionized am-
              bodies of rotifers produced by feeding that food (from Imada 1984).                     monia concentration.

                                                                                                77




	
		Figure 5
The supplementary effect of fat-soluble vitamins on the growth of the 
rotifer. Vitamins were added to the basic food suspension consisting
of 200 mg/mL of baker's yeast and 1.4 mg/mL of vitamin B 12. (A) Rela-
tive r and R for each fat-soluble vitamin at different concentrations
in individual culture; (B) Total increase in population of the rotifer in
food supensions supplemented with fat-soluble vitamins at different
			combinations in batch culture.

															Figure 6
	The rotifer can tolerate relatively low oxygen levels. Imada		Relations between oxygen content and growth rate of two groups of
(1984) observed an inverse relationship between the oxygen				rotifer, one fed only AMT floe and one only co-yeast (from Imada 1984).
content of mass-culture tanks and the growth rate of rotifers
fed with AMT flocs or w yeast (baker's yeast strengthened
with essential fatty acid) (Fig. 6.) This appears to indicate			above. An abrupt change of water temperature may directly
that the rotifer grows better at low oxygen levels. However,			or indirectly affect the growth of a rotifer culture. Suppressed
this was not the case when marine Chlorella was provided				growth is often observed during a period of shift of domi-
as a food. It seems likely that this relationshop occurred				nant strains. Also, the formation of large numbers of dor-
because the bacteria which produced vitamin b 12 in yeast-				mant eggs sometimes results in a sudden decrease of the 
fed vultures are facultative anaerobic bacteria.					rotifer population. We often observe that suppressed growth
	In mass culture of the rotifer there are many cases of sud-			is accompanied by an increase indiatoms or protozoa in the 
den decrease or suppressed growth of the population. Some				cultures.
of these could be explained by physiological responses of 
the rotifer as described above. However, we have many cases
which seem to have no relation to the causes mentioned

78





               Problems for future study                                                                Higashihara, T.S., S. Fukuoka, T. Abe, 1. Mizuhara, 0. Imada, and
                                                                                                          R. 111rano
                                                                                                            1983 Culture of the rotiferBrachionusplicatilis using a microbial flocs
               Many problems remain to be solved to establish more reliable                                    produced from fermentation syrups. Bull. Jpn. Soc. Sci. Fish. 49:
               rotifer culture techniques: 1) Select or produce the suitable                                   1001-1013.
               size of rotifer with a faster and more stable growth, 2)                                 Hino, A., and R. Mrano
               establish reliable mass-culture techniques of marine Chlorella.                              1980 Relationship between body size of the rotifer Brachionusplicatilis
                                                                                                               and the maximum size of particles ingested. Bull. Jpn. Soc. Sci.
               or find substitute phytoplankton, 3) clarify the nutritonal                                     Fish. 46:1217-1222.
               requirements and to formulate completely artificial diets for                            Hino, A., Y. Nogami, and R. Hirano
               the rotifer, 4) completely clarify the environmental condi-                                  1981a Fundamental studies on the mass culture technics of the rotifer
               tions regulating population growth, and 5) understand the                                       Brachionusplicatilis making use of the secondary products of waste
               factors controlling bisexual reproduction.                                                      water treatment-1. Rotifer culture providing with activated sludge.
                                                                                                               Suisan Zoshoku 28:174-178 (in Jpn.j.
                                                                                                            1981b Fundamental studies on the mass culture technics of the rotifer
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                      Saibai 32:41-50 [in Jpn.].                                                               Univ. 56:21-23.
               Birch, I.C.                                                                              Ibrata, H., and Y. Mori
                    1948 The intrinsic rate of natural increase of an insect population.                    1%7 Mass culture of the rotifer fed baker's yeast. Saibai Gyogyo
                      J. Anim. Ecol. 17:15-26.                                                                 5:36-40 [in Jpn.l.
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                    1978 Food selectivity of the rotifer Brachionus plicatilis feeding on                   1983 The rotifer Brachionus plicatilis - Biology and mass culture
                      phytoplankton. Mar. Biol. 45:105-111.                                                    (ed. Japan. Soc. Sci. Fish.). Suisangaku set. 44:52-68. Koseisha-
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                           Zool. Mag. (Tokyo) 91:657.
                    Yasuda, K., and N. Taga
                         1980 Culture of Brachionus plicatilis Mfiller using bacteria as food.
                           Bull. Jpn. Soc. Sci. Fish. 46:933-939.
                    Yu, J.P., and K. Hirayama
                         1986 The effect of un-ionized ammonia on the population growth of
                           the rotifer in mass culture. Bull. Jpn. Soc. Sci. Fish. 52:1509-1513.




























                                                                                                    80







            EffeetS of EnVironMental                                               Along the Okhotsk Sea coast of Hokkaido in Japan (Fig. 1)
                                                                                   before 1973, production of the Japanese scallop Patinopecten
            Instability on the Growth                                              yessoensis depended on natural resources. Until 1945, the
                                                                                   annual yield of scallop fluctuated markedly, but the highest
            of the Japanese Safflop                                                yield reached 15 thousand tons in Sarufutsu and other
                    0                                                              grounds. However, yields decreased each year after 1945.
            PcWhopecten yessoensis in                                              In 1973, sowing-culture began on a large scale in Sarufutsu.
                           A                                                       This sowing-culture was a great success, reaching an annual
            Abashiri Sowing-Culture                                                yield of 40 thousand tons in 1984. Subsequently, sowing-
                                                                                   culture has spread along the Okhotsk Sea coast.
            Groun&                                                                    In Abashiri Bay (Fig. 1) sowing-culture began in 1978.
                                                                                   In 1980, however, high mortalities and markedly slow
                                                                                   growth of sown scallops were observed. We have studied
                                                                                   the growth and survival of scallops in Abashiri sowing-
            NAOJI FUJITA                                                           culture grounds from 1982 to 1984.
            Faculty of Agriculture
            Tohoku University
            Amamiyarnachi-Tsutsurnidoti                                            Sowing-culture on the
            Sendai 980, Japan                                                      Okhotsk Sea coast
            KATSUY0SHI MORI                                                        The Sea of Okhotsk is a semi-closed sea surrounded by land
            National Research Institute of Aquaculture                             and islands and has four distinct characteristics. (1) The sur-
            Fisheries Agency                                                       face layer above 50 in depth, the Okhotsk Surface Water,
            Nansei, Mie 516-01, Japan                                              has very low salinity (<32.50/oo). (2) Drift ice develops and
                                                                                   covers 80% of the Sea of Okhotsk in winter. (3) The Soya
                                                                                   Warm Water, of high temperature and high salinity, enters
            ABSTRACT                                                               into this sea through the Soya Straits (Fig. 1) from the Sea
                                                                                   of Japan. The Soya Warm Water flows along the coast of
            Environmental instability in Abashiri waters is caused by many         Hokkaido and reaches the Siretoko Peninsula March to
            factors, including geographical features, hydrographic struc-          October. (4) The continental shelves are as wide as 200 kni
            ture, drift ice, and atmospheric conditions. Therefore, the            in the western part of this coast and become narrower to the
            degree of instability varies year to year. The growth of scallops      east, being only 16 kin off Abashiri Bay.
            is affected by environmental instability, especially by temper-           Squares marked A, B, C, and D (Fig. 1) are rotating
            ature fluctuations which depress feeding activities spring to          sowing-culture grounds. Measurements of water quality and
            summer. Then, growth is slower than in the western part of             other elements were carried out at Station A in Abashiri Bay
            the Okhotsk Sea coast, and fluctuates according to the degree          and Station D off Lake Notoro (Fig. 1).
            of environmental instability each year. It is difficult to mini-          In these sowing-culture grounds, the removal of starfish
            mize such environmental effects on the growth of scallops.             is carried out by dredging. After this, from 60 to 100 million
            However, the recatch:relme ratios of sown scallops have                scallop juveniles, 1 year old, are sowed in June. After 2
            increased year after year to 40%. This demonstrates that               years, the sown scallops are harvested.
            reasonable methods can bring about an abundant harvest even
            in inadequate environments such as Abashiri Bay.                          In Abashiri A, sowing-culture began on an industrial scale
                                                                                   in 1978. However, it was found in 1980 that the survival
                                                                                   ratio was only 4.2 % and growth was slower than on the other
                                                                                   grounds of the Okhotsk Sea coast. Total wet weight of sown
                                                                                   scallop at 3 years of age in Mutsu and Funka Bay, Okhotsk
                                                                                   Sea coast, and Abashiri A were 250, 170, and 80 g, respec-
                                                                                   tively. Thus scallops in Abashiri Bay grew to only one-third
                                                                                   the weight of those in Mutsu and Funka Bay.
                                                                                      Scallops have been known to grow well in Abashiri D,
                                                                                   as in other grounds located in the western part of this coast;
                                                                                   however, they grow poorly in Abashiri Bay. Therefore, we





                                                                               81











                                                Soya  @t r.
                                                                 Sea
                                                                  o f
                                                                01 hotsk
                                            a                        Pen. Shi etoko
                                           f
                                         J pan
                               44*N


                                                       Hokkaido



                                                                                      E                               4  O'E
                                 42*                                                     VSef.
                                                                                                                    1,000
                                                                                            Okhotsk
                                                   Mu:su Bay

                                                                                          D                         Soo
                                                                                    SI.n. D,`.j
                                                                          L. Sa.
                                40'                                                                                200 rn

                                                                                                    Abashiri Bay
                                         146E        142'       144'                 @@I'       I                    .. . 44' N
                                                                                                    'j Stn. A

                                                                    0                      50km



                                                                          Figure I
                             Ucation of the scallop grounds in the study area. Squares marked AL, B, C, and D are rotating sowing-culture grounds.







                                                            N


                                                              0







                                                                                                     Soya
                                         o                                                            Warm
                                                                                                        Water

                                        50
                                                   10         Soya
                                       V00
                                                              Warm
                                                                Water
                                       .'50

                                        200





                                                                          Figure 2
                                    Schema of hydrographic structure generally observed immediately after the disappearance of drift
                                                                ice from the Okhotsk Sea coast.




               expected to find distinct differences in environmental con-       Environmental factors
               ditions between Stations A and D. However, the results of
               many water-quality measurements did not differ between            Winter drift ice
               Stations A and D during 3 years. Therefore, we need to            Drift ice causes extremely low water temperature, which
               consider other factors contributing to the inadequate envi-       represses the growth of scallops. The duration of the drift
               ronment for scallops in Abashiri Bay.                             ice period varies markedly between years, from 2 to 5 months
                                                                                 in Abshiri, depending on climatic conditions.
                                                                             82







                 Spring upwelling
                 After the disappearance of drift ice from this coast in March                                                                                                                         -20
                 or April, the Okhotsk Surface Water spreads over the sur-                                                                                                              St n. A, 30 rn
                 face layer (Fig. 2). Along the western part of this coast, from
                 Soya Straits to near Lake Saroma, the Soya Warm Water
                 (S.W.W.) occupies the entire water column and flows along-                                                                                                                             15
                 shore. Approaching Abashiri Bay, the S.W.W. sinks along                                                                    ........ 1982
                 the deepening bottom, and then, off Abashiri Bay, the                                                                               1983
                 S.W.W. flows along the bottom at a depth of 100 or 200                                                                              1984
                 meters. These hydrographic structures are caused by the                                                       20-                                                                     -10
                 higher density of the S.W.W. and the deeper bottom around
                 Abashiri Bay. In any case, the S.W.W. rises to the surface
                                                                                                                                                                                                            CL
                 in summer. We can assume two processes which raise the                                                                                                                                     E
                 S.W.W. to the surface.
                                                                                                                               15-                                                                       5
                     One of these processes is the decreased density in accor-
                 dance with the rise in temperature of the S.W.W. With this                                                                        0/                                   Stn. D, 30m
                 process only, it takes 2 or 3 months for the S.W.W. to reach                                                0
                 the surface layer. Therefore, temperatures in the coastal water                                              4,10-                                                                      0
                 rise gradually, as shown in Figure 3, Station A, in 1982.
                     Another process is wind-induced upwelling. In this region,                                                                                                                   -1-2
                                                                                                                              E
                 offshore. Although the east wind is very small in this region,
                 upwelling induced by the east wind moves the surface water

                 the south wind also moves the surface water offshore.                                                           5-
                     In the spring of 1983, marked upwelling occurred with
                 the following processes. A strong south wind blew contin-
                 uously for more than a week from the end of March to early
                 April and moved the drift ice offshore from Abashiri Bay.                                                       0
                 At the same time, the surface water of the coast was trans-                                                   -21
                 ported offshore. Then the bottom water, the S.W.W., was                                                            Mar.      Apr.      May       Jun.       Jul.     Aug.       Se p.
                 transported to the shoreline. Thus, the temperature rose
                 rapidly along the coast (Fig. 3). At the same time, the spring                                                                              Figure 3
                 phytoplankton bloom was removed and replaced by water                                                Seasonal temperature variations at 30-m depth at Abashiri Stations A
                 containing low levels of nutrients (Fig. 4). Along this coast,                                                               (upper) and D (lower), 1982-84.







                                                                                        Stn. A
                          250-                                                                        1982
                                                                                                      1983
                                                                                                      1984
                                                                 50-
                     c:7' 200-
                      E                                          40-

                      E
                          150-                                   30-

                                                                                                             V
                      C                                          20
                      CL                                                                                          k"
                      0
                      8   too-
                                                                 10                       A

                                                                 0     J.      J.       A.       S.        0.      N.
                          50-
                                         4


                            0                                                                                                              Figure 4
                               mar.     Apr.     May      Jun.     Jul.    Aug. Sep.         Oct.     Nov. Dec.                            Seasonal variations in cumulative (0-30 m) chloro-
                                                                                                                                           phyll a at Abashiri Station A, 1982-84.


                                                                                                                83











                                                                                                                20
                                                    4-


                                                  N 2-

                                                                                         .iV
                                                    0                                                           15
                                                                  V                 An


                                                'S 2-
                                                 d;


                                                    4-
                                                                                                                102
                                                 CL 4-
                                                                                                                  E

                                                3: E2-
                                                  -0        A@V          4NW",
                                                                                                                5


                                                  W 2

                                                                                           Wind speed
                                                    4                                      Temperature
                                                                                                                0


                                                                                                                1-2
                                                          Apr.     May      Jun.     Jul.    Aug.     Sep.



                                                                             Figure 5
                                             Daily Paean temperature variations (dotted line) at 28-m depth of Abashiri Station
                                             D measured with Ryan Model J, and daily mean wind speed (solid fine) observed
                                               by Abashiri Regional Meteorological Observatory, April-September 1984.



               a phytoplankton bloom is expected to develop once a year,             off Abashiri Bay, the S.W.W. occupies the upper layer from
               although the scale of the spring bloom fluctuates widely. The         the surface to about a 100-meters depth (Fig. 6). The tem-
               largest amoung of chlorophyll a was 270 mg/m2 in 1984,                perature gradients extend horizontally. The area between the
               and the smallest was 60 mg/m2 in 1983 (Fig. 4).                       bottorn of the S.W.W. and the sea bottom is occupied by
                  The scallop spawning season is May to June in this area.           cold water. Under this structure, upwelling causes a sudden
               Spring phytoplankton bloom is thought to be the major food            temperature drop and many other mechanisms cause tem-
               source for scallops just prior to spawning. These fluctuations        perature fluctuations on this coast.
               of spring bloom are considered to be a disadvantage for the             In August of 1984, rapid temperature changes were
               spawning of the scallops.                                             observed most frequently (Fig. 7). Daily cyclic changes
                  The same phenomena were observed in the next year,                 ranging from 3 to 5'C were observed in early August,
               1984. From April to June, three temperature peaks were                probably caused by internal tides under the two-layered struc-
               observed (Fig. 5), caused by upwelling of the S.W.W. in-              ture shown in Figure 6. The rapid fall in temperature of 13'C
               duced by strong south winds. Thus, the S.W.W. was brought             during 20-25 August was caused by upwelling induced by
               up to the upper layer. At the period indicated by the arrow           a Strong south wind. These rapid temperature changes are
               in Figure 5, the S.W.W. reached the surface. After this               the main factors that cause environmental instability.
               period, the upper layer of the water mass was replaced by               It is clear that daily temperature ranges are wide from May
               the lower, and this upwelling caused the sudden fall in               to mid-September. Then, after mid-September, the daily
               temperature.                                                          range becomes narrow (Fig. 5) because the layering struc-
                                                                                     ture, of the water masses is destroyed by the cooling of the
               Summer temperature fluctuation                                        surface water.
               After reaching the surface, the S.W.W. flows alongshore,              Intermediate cold water in summer
                                                                                                   nd





































               occupying the entire water column off Lake Notoro, and
               temperature gradients extend vertically (Fig. 6). The same            Finally, environmental instability along this coast is due to
               structures are observed generally in the western part of this         the approach of the Intermediate Cold Water (I. C. W.) to the
               coast. It is believed that this hydrographic structure prevents       coast. This I. C. W. is of very low temperature, from - 1. 8
               upwelling and temperature fluctuations. On the other hand,            to +2'C, and exists below the 50-m depth even in summer.

                                                                                84
















                                                                 N










                                               0
                                                   'Ice
                                               50
                                                                                                         @w

                                            '15o
                                                                                          @V.
                                               2
                                               00



                                                                        Figure 6
                                       Schema of hydrographic structure generally observed in summer along the Okhotsk
                                       Seacoast. S.W.W. =Soya Warm Water; I.C.W. = Intermediate Cold Water; bold
                                                               lines  temperature gradients.




                                               20




                                               151







                                               E10-
                                               41





                                               51
                                                        5        10        is        20         25          31
                                                                          August


                                                                        Figure 7
                                        Two-hour temperature variations at 28-m depth of Abashiri Station A measured
                                                             with Ryan Model J, August 1984.




              Figure 8 shows the hydrographic structure during Sep-             hydrographic structure easily caused the temperature fluc-
            tember of 1984. Off Lake Notoro, the front of the I.C.W.            tuation nearshore. On this coast, temperatures generally do
                                                                   198
                                                                                                    ev
                                        m      offsho
                                                                                               how
            is usually located 25-40       iles      re (Ohtsuki        3).     not fluctuate;        er, it seems that temperature fluctua-
            However, it was only 9 miles offshore in 1984, the closest          tions should occur once every 10 or 20 years by the approach
            approach to shore in 18 years. Then, the S.W. W. condition          of I.C.W. to this shore.
            became unusual, that is, the temperature gradients extended
            horizontally off Lake Notoro as off Abashiri Bay. This


                                                                            85















                                                                    N










                                                 0 01
                                                    411
                                               50
                                                           0
                                                                                                             W.
                                              .10
                                                                                                            C
                                              0150
                                               2                                             W
                                                                                            C




                                                                           Figure 8
                                           Schema of unusual hydrographic structure obsened in September 1984 along the
                                           Okhotsk Sea coast. S.W.W. = Soya Warm Water; I.C.W. = Intermediate Cold
                                                            Water; bold lines  temperature gradients.



               In situ biodeposition
               rates and growth                                                                 E

               In order to understand the relationships between environmen-
               tal conditions and feeding activities, in situ biodeposition rates
               of scallops were measured. The term "biodeposits" coined
               by Haven and Morales-Alamo (1966) means "feces and
               pseudofeces" which are produced by filter-feeding animals,
               such as scallops, and deposited on the bottom.
                 In situ biodeposits were collected with sampling apparatus
               designed by us (Fig. 9). Two-year-old scallops were freshly
               caught from the bottom of each station. One apparatus with
               four scallops and one control apparatus without scallops were
               placed on the bottom. After one day, biodeposits were col-
               lected and dry weight measured.
                 It was expected that biodeposition rates would increase with
               increases in the amount of food. However, the results did
               not show such relations (Fig. 10). It is concluded that the
               extremely low biodeposition rates obtained in ice-covered
               Lake Notoro in winter (open circles, Fig. 10) resulted from
               depressed feeding activities caused by the extremely low                           56 30 cm
               temperature (- 1.6*C). We consider that biodeposition rates               Transparent
               below 200 mg/individual per day are also depressed by en-                       Polyvinyl
                                                                                                                                     E
                                                                                                  Chloride
               vironmental factors perhaps related to the rapid and frequent
               changes in temperature in Abashiri waters.
                 In consideration of some studies on thermal adaptation                      Weight
               (Somoero 1969, Dickie and Medcof 1963), we have assumed
               that aquatic poikilotherms, such as scallops, that live on the



                                                                          Figure 9
                                              Sampling apparatus used for collection of
                                                      biodeposits of Japanese scallops.

                                                                               86











                                                                                                        Stn. A                        Stn- A        Stn. D


                   300-


                                                                                     15-                                                                        -200


                 C


                 E200-



                                 %
                 C                                                                   10-           F-                                                     I     -100=
                 0                                                                                                                                                  (A
                                                                                                                                                                    0
                                                                                                                                                                    CL
                 0100-
                           0                                                                                                                                        0
                                                                                          Chia 0.61                   G96           1.16                            CD
                                              0                                                                                                         0.19
                 0         0                                                              (,Ug10


                                                                                                                                     23                         0
                                                                                          July    23   24   25 26     27                  24   25 26 27
                               O@5        1.0       1.5       2.0                                                     Date
                                Chlorophyll   a (,ug/l)
                                                                                                                      Figure 11
                                   Figure    10                               Biodeposition rates of 2-year-old scallops (vertical columns) at Abashiri Stations A Oeft)
             Biodeposition rates of 2-year-old scallops in relation to        and D (right). Scallops used were captured at Station A. Temperatures were measured
             chlorophyll a of ambient water in Abashiri Bay (0) and           with Ryan Model J (solid line) and with water sampled (dashed line). Horizontal lines
                     ice-covered Lake Notoro (0), 1982-84.                    show sampling periods of biodeposits. Amounts of chlorophyll a were obtained at the
                                                                                               bottom of Stations A and D on 23 and 27 July 1984.





             sea bottom cannot adapt quickly to rapid changes of tem-                          Seasonal variation of biodeposition rates
             perature. We examined this assumption by in situ measure-                         Seasonal variations in amount of biodeposits are calculated
             ments. The biodeposition rates obtained at Station A with                         with biodeposition rates obtained in Abashiri waters (Fig.
             scallops caught freshly at the same place were 180 mg/day                         12). The numbers in every column in Figure 12 indicate the
             on 23-24 July, and decreased to 138 mg/day with an increase                       amount of biodeposits produced during every period. From
             in temperature of YC during three successive days (left,                          September to December, temperature fluctuations are not so
             Fig. 11).                                                                         marked, as mentioned previously, and the scallops feed con-
                The right graph in Figure I I shows the measurements at                        stantly in the stable environment. However, even these
             Station D with scallops caught at Station A. During the period                    amounts of biodeposits are not large, because of the small
             23-24 July, scallops were exposed to a sudden rise and fall                       amounts of food available during this season. In Mutsu Bay
             in temperature over the range of about 5'C and the biodep-                        where the scallops grow faster than in Abashiri
             osition rate was reduced to 40 mg/day. This is only 20%                   '
             of that of Station A and as low as that caused by the extremely
             low temperatures. During three successive days, the bio-
             deposition rate increased a little, but under these fluctuating
             temperature conditions, it was only half that of Station A.
                From the results above and knowledge of the effects of                                 600-
             thermal changes, we believe that feeding activities are fre-
             quently depressed by fluctuating temperatures from spring
                                                                                                      400
             to summer in Abashiri Bay.
                                                                                                  0
                                                                                                  cL@z 200-
                                                                                                                 32.6 g
                                                                                                            1                         6.9 g                    4 g
                                                                                                         0                                                E10.
                                                                                                  a]        IS I  OINID_ JTF_TM 'AIM IJ IJ                       A
                                                                                               I                                                                         I

                                                                                                                             Figure 12
                                                                                               Seasonal variations in amounts of biodeposits of a 2-year-old scallop
                                                                                                                      in Abashiri Bay, 1982-84.





                                                                                          87







                  Bay, the biodeposition rates were almost identical with that
                  of Abashiri Bay in this season (Fuji and Hashizume 1974).                               180-                                                0 0
                  In winter (January-April), the extremely low temperature                                                                0
                  over a fairly long period depresses feeding activities in                               160-         0              0
                  Abashiri waters. In Mutsu Bay, the most active feeding is
                                                                                                          140-
                  done in this season, and the amount of biodeposits reach                                            0       0, 1983
                  80.9 g (Fuji and Hashizume 1974). This active feeding in                          -C,4120 -
                  Mutsu Bay is supported by the spring phytoplankton bloom                          2
                  and by higher temperatures (4-8'Q than Abashiri waters.                           SD100 -                    B, 1982
                  From spring to summer in Abashiri waters, the amount of                           3:
                                                                                                    Z     80
                  biodeposits; increases slightly, but it is still small, caused by                 3:                   ya
                  temperature fluctuations as mentioned previously. Thus, the                                                         X
                                                                                                          60-                            X- A- r
                                                                                                                               X
                  annual amounts of biodeposits; produced by a 2-year-old                                                        C, 1984
                  scallop in Abashiri and Mutsu Bay are 59.4 and 151 g (Fuji                              4
                  and Hashizume 1974), respectively. The Abashiri:Mutsu
                  ratio is 0.39, being similar to the ratio of total weight.                              20-
                    Therefore, we conclude that the causes of slow scallop                                0
                  growth in Abashiri Bay are the extremely low temperature                                  Apr.    May       Jun.     Ju 1.     Aug.     Sep.
                  in winter and temperature fluctuations from spring to sum-                    I                                                                      I
                  mer. The magnitude of this fluctuation should vary every                                                    Figure 13
                  year. In the western part of the Okhotsk Sea coast, includ-                   Growth of 2- to 3-year-old scallops at Abashiri Stations B (6 1982),
                  ing Abashiri D, the winter temperature is low, but temper-                              D (0 1"3), and C (x 1984), April to September.
                  atures from spring to summer are stable at which time the
                  scallops grow well.
                  Spring-summer scallop growth                                                            200-                                                -40
                  Figure 13 shows total wet weight of scallops from April to
                                                                                                                                        0
                  September for 3 years. The weight is the average of 30 to                                                            P
                  2000 scallops obtained by harvesting operations in each year.                           ISO-                                                -30
                  They show various growth rates in this season, such as rapid
                  increase in weight from April to May (Abashiri B 1982,
                  Abashiri D 1983) and decrease in weight from May to June
                  caused by spawning. However, it is clear that in Abashiri                         451
                  B 1982 and Abashiri C 1984 the scallops grew very slowl                                                                                 0
                                                                                        y
                                                                                                          10                                                   20
                  from July to September. This slow growth is probably caused                       Z
                  by the rapid temperature fluctuation as mentioned above.                                                     0
                                                                                                    2

                                                                                                                                                 0
                  Conclusions                                                                             50-                                                -10  cc

                  Overall results of sowing-culture from 1978 to 1985 are
                  shown in Figure 14. The highest weight was 170 g in 1983
                  at Abashiri D. In the other grounds of Abashiri Bay, Aba-                                  A        C        B       D         C       B
                  shiri A, B, and C, the weight fluctuated between 140 and                                of  I       I        I        I        _L       L 0
                  60 g. It is clear that there is no trend toward increase or                               1980    1981      1982    1983     1984    1985
                  decrease in weight. We conclude that these fluctuating growth                                                  Year
                  rates reflect the environmental instability in Abashiri waters.
                    On the other hand, the recatch: release ratio increased year                                              Figure 14
                  after year to about 40% in 1985. This indicates that there                    Yearly variations of total wet weight of 3-year-old scallops in Septem-
                  is no relationship between growth and survival. The decrease                  ber (0) and release:recatch ratio (0) in the Abashiri scallop grounds
                  of predation by starfish may explain the trend of increase                                               (A-D), 1980-85.
                  in the survival ratio through the years. It is well known that
                  starfish are the main predator of scallops. In these sowing-
                  culture grounds, the removal of starfish has been carried out
                  successively since 1978. It is believed that the numbers of
                  starfish have gradually decreased and the survival ratios

                                                                                           88







              have increased year after year. Actually, a marked decrease
              in numbers of starfish from 0.39/m2 (June 1980) to 0.07/m2
              (July 1985) was observed in Abashiri A.
                 In the present study, we determined that environmental
              instability was especially marked in Abashiri Bay, causing
              slow and fluctuating growth. However, continuous efforts
              to eliminate predators such as starfish and to collect large,
              healthy seed scallops and release them at both a suitable time
              and a rational population density have brought about an abun-
              dant harvest even in Abashiri Bay, though the weight of
              individual scallops is small.


              Acknowledgments

              We wish to express our appreciation to Kazuhiko Konishi,
              Faculty of Science, Tadashi Nomura, and Satoshi Nishizawa,
              Faculty of Agriculture of Tohoku University, for their ad-
              vice in planning research. Our thanks also to the members
              of Abashiri Fisheries Cooperative Association, Hokkaido,
              who assisted our study.


              Citations


              Dickie, L.M., and J.C. Medcof
                   1963 Causes of mass mortalities of scallops (Placopecten ntagellanicus)
                     in the southwestern Gulf of St. Lawrence. J. Fish. Res. Board Can.
                     20:451-482.
              Fuji, A., and M. Hashizume
                   1974 Energy budget ofa Japanese common scal[lop, Patinopecren yes-
                     soensis (Jay), in Mutsu Bay. Bull. Fac. Fish. Hokkaido Univ.
                     25:7-19.
              Haven, D.S., and R. Morales-Alamo
                   1966 Aspect ofbiodeposition by oysters and other invertebrate filter
                     feeders. Limnol. Oceanogr. 11:487-498.
              Ohtsuki, T.
                   1983 Variations of "Intermediate Cold Water-front" in summer,
                     southwestern Okhotsk Sea. J. Hokkaido Fish. Exp. Sm. 40:211-226.
              Somoero, G.N.
                   1969 Enzymic mechanisms of temperature compensations: immediate
                     and evolutionary effects of temperature on enzymes of aquatic poi-
                     kilotherms. Am. Nat. 103:517-530.






























                                                                                            89






             Mantis Shrimp:                                                            The mantis shrimp, Oratosquilla oratoria (de Haan), is a
                                                                                       stomatopoda crustacean inhabiting the sandy mud bottom in
             its fishery and                                                           the coastal waters of temperate and subtropical regions of
                                                                                       the northwest Pacific Ocean. In Japan, this shrimp has been
             Biological Production                                                     caught in large quantities (-5000 tons per year) in the coastal
                                                                                       waters of Tokyo Bay, Ise Bay, and Seta Island Sea, and used
                                                                                       for food in "Sushi. " The fishery in Tokyo Bay (the process
                                                                                       from fishing to forwarding) is described in this paper as one
             MAKOTO YAMAZAKI                                                           example of the fishery for this shrimp. Also the process of
             Seikai National Fisheries Research Institute                              biological production of adult mantis shrimp is described,
             Kokubu-inachi, Nagasaki 850, Japan                                        which is important as the basis of the explanation of popu-
                                                                                       lation dynamics of this shrimp.


                                                                                       Fishery in Tokyo Bay

                                                                                       The mantis shrimp is one of the most important fishing targets
                                                                                       in Tokyo Bay. The shrimp fishery is conducted with the aid
                                                                                       of a Danish seine boat (Fig. 1) carrying a type of hand trawl.
                                                                                       After trawling for about one hour, the net is hauled (Fig.
                                                                                       2) and the mantis shrimps are selected from the catch on deck
                                                                                       (Fig. 3). Shrimps are transported live in holding tanks and
                                                                                       are boiled soon after landing (Fig. 4). The carapace (cepha-
                                                                                       lothorax) and both sides of the abdominal exoskeleton are
                                                                                       cut with scissors (Fig. 5) and the shells are removed by hand
                                                                                       (Fig. 6). The shucked shrimp, graded by size, are packed
                                                                                       in plastic cases (Fig. 7) and forwarded (Fig. 8).
                                                                                         The fishermen engaged in the Tokyo Bay fishery have
                                                                                       restricted themselves to the ratio of 2:1 days (i.e,, 4 days
                                                                                       operation per week) to ensure the shrimps' stable produc-
                                                                                       tion and to preserve its price in the market by controlling
                                                                                       the volume produced. Compared with other production areas,
                                                                                       that of Tokyo Bay is relatively stable.


                                                                                       Process of biological production

                                                                                       In contrast to the Tokyo Bay fishery, the annual catch of
                                                                                       mantis shrimp fluctuates widely among the prefectures. To
                                                                                       maintain the catch at a certain level, two problems must be
                                                                                       resolved: One is to develop techniques of resource manage-
                                                                                       ment, and the other is to intensify efforts for artificial recruit-
                                                                                       ment to the shrimp population. To resolve these problems,
                                                                                       systematic ecological investigations of the natural popula-
                                                                                       tions and of the primary factors affecting population dynamics
                                                                                       are needed. Until now, however, these kinds of studies have
                                                                                       been rare.
                                                                                         A series of investigations was undertaken by the author
                                                                                       to determine the biological production of adult mantis shrimp,
                                                                                       based on the ecological aspects of reproduction, growth, and
                                                                                       food consumption, and to clarify the distribution of energy
                                                                                       from food intake to the growth of reproductive organs and
                                                                                       other body parts. All shrimp used in this research were ob-
                                                                                       tained from Mutsu Bay, Aomori Prefecture of northern
                                                                                       Japan.

                                                                                  91
























                                                                                                                           Ilk.



                                                                                                             AdIL





                                                                                                                        I Y



                                                                                                                                                              Figure 1
                     61
                                                                                                                                                              Danish seine
                                                                                                                                                              boat carrying
                                                                                                                                                              a type of hand
                                                                                                                                                              trawl.
                     EL
                                                                                                                                                              Figure 2
                                                                                                                                                              Net hauled
                                                                                                                                                              after about
                                                                                                                                                              one hour
                                                                                                                                                              trawling.

                                                                                                                                                              Figure 3
                                                                                                                                                              Mantis shrimps
                                                                                                                                                              selected from
                                                                                                                      4
                                              1!                    A, -4                                                                                     the catch on
                                                                                                                                                              deck.

                                                                                                                                                              Figure 4
                                                                                                                                                              Mantis shrimps
                                                                                                                                                              boiled soon
                                                                444                                                                                           after landing.

                                                                                                                                                              Figure 5
                                                                                                                                                              Cutting both
                                                                                                                                                              sides of the
                                                                                                                                                              abdominal
                                                                                                                                                              exoskeleton
                                                                                                                                                              with scissors.

                                                                                                                                                              Figure 6
                                                                                                                                                              Shucking the
                                                                                                                                                              shells by hand.
                                                                    T
                                                                                                                                                              Figure 7
                                                                                                                                                              Shucked
                                                                                                                                                              shrimps packed
                                                                                                                                                              in plastic cases.

                                                                                                                                                              Figure 8
                                                                                                                                                              Shrimps prior
                                                                                                                                                            I to forwarding.

                                                                                              92













                                                                                                 0 0 0
                                                    @@
                                              @                                                     F
                                                          AM


                                                                                                                   @
                                                    FEMALE                                    MALE               @@
                                        00                        C_                                             @@
                                        oo
                                         00
                                          00                                                                   @ @
                                           00
                                            00                                                             @
                                              0                                             0  0      00     @@
                                                                                            0 0    0 0 0


                                                                         Figure 9                              developing
                                   Scheme of the reproductive cycles of the mantis shrimp. [A] Recovering,FO
                                         preniatring, li] maturing, E::] spawning (female) and sperirn-ejecting (male)
                                                                           period.



           Reproductive cycle                                                    (Table 1). From these results, adult growth in length appeared
           The reproductive cycle of mantis shrimp was described by              stepwise (Fig. 11). From three groups of pre- and post-
           Yamazaki and Fuji (1980), summaried as follows.                       moulting body length presented in Figure 11, the following
             The developmental processes of germ cells in both sexes             equation is derived by means of the graphic method of Hiatt
           were arbitrarily categorized into stages by histological tech-        (1948).
           niques. On the basis of these stages of the development of                            L,,+, = 0.755L,, + 4.743                      (1)
           germ cells, the maturation processes were classified into four
           stages in the ovary and five stages in the testis. The value          where L,, and L, +I are the linear dimensions of pre- and
           of the gonad index, which is the ratio of the wet weight of           postmoulting, respectively.
           gonadal tissues to the total body weight, is correlated with            The value of 0.755 shows that its growth pattern is of the
           the gametogenetic development in both sexes.                          retrogressive geometric type (Kurata 1960), and that the
             The annual reproductive cycle in the female population of           amount of increase at successive moultings decreases in pro-
           mantis shrimp was broadly classified into the following five          portion to the increase in initial premoulting body length.
           periods, according to the course of seasonal variation of the
           gonad index and the duration of active appearance of each             Changes in body weight and body component weight
           gonadal stage: 1) Recovering (Aug-Sept), 2) developing                (integument, muscle, hepatopancreas and gonad) Length-
           (Oct-Nov), 3) prematuring (Dec-Feb), 4) maturing (Mar-                weight regression equations were obtained monthly from the
           May), and 5) spawning (June-July). In similar procedures,             rearing experiment, and the slopes of these equations were
           the cyclical reproductive processes in the male population            unified to a value by statistical analysis (Table 2). From these
           were divided as follows: 1) Recovering (July), 2) develop-            equations and the body length derived from the equation (1),
           ing (Aug-Sept), 3) prematuring (Oct-Dec), 4) maturing                 the seasonal body-weight change was derived (Fig. 12). Body
           (Jan-Apr), and 5) sperm-ejecting (May-June) (Fig. 9).                 weight (and body length) increases by a large increment after
                                                                                 moulting, and there is a remarkable variation resulting from
           Growth pattern                                                        maturation and spawning in the female.
           Change in body length Mantis shrimps were sampled                        The regression equations of body weight-dry component
           monthly by bottom gill net (7.6 cm mesh) April 1976-                  weight were obtained from bimonthly dissections. Based on
           September 1977 and May 1981-December 1982. From                       these equations, the seasonal changes in dry weight of body
           polymodal length-frequency distributions, several fitted              components were derived from any body length without
           normal curves were analyzed by the probability graph paper            dissections (Table 3). The striking seasonal variations of dry
                                                                                 weight of body components reflect the accumulation and con-
           method of Harding (1949) (Fig. 10). And from these nor-               sumption of substances concerned with spawning and moult-
           mal curves, the seasonal fluctuation in mean body length of           ing in females. However, in males there are no large changes
           each cohort was obtained. The rearing experiment for the              throughout the year except the increment at moulting.
           observation of moulting was made September 198 1 -Decem-
           ber 1982, and moulting was observed only August-October

                                                                             93





                                           11 Ap, 2676
                                           0





                                           10 May23

                                           01 J,n*12                                    rl                            Oct to
                                           July25
                                           a    n        n Ak,                                               0
                                           ISep 20                                                                    Oct 29
                                           01        :@@ n
                                           Oct 10         1


                                                                                                                      Me, 14'
                                                21


                                           0
                                 C         Dec 13                                                                     A118
                                 4)
                                           0                                                                 0

                                                                                                                      May 28
                                           M,yll'77

                                 U_        1, 2                   1
                                           J@ 2
                                           J@ 2                                                                                                      ea

                                           June 16                                                                    June 13




                                           July 2
                                           JJ01, 2J13                                                        0i S.P20
                                           Aug 12                                                                     Oct 17
                                           H                                                n                         Dec 6                                                       Figure 10
                                                                     Rme@&                                   '1to              13                  16             t-              Histograms showing firequencies of body length and
                                           0               13                  15                19                                                                               several fitted normal curves calculated by the prob-
                                                                                  Body                length          (cm)                                                        ability graph-paper method. Broken lines indicate
                                                                                                                                                                            I     the flow of mean body length of each cohort.





                                                                                                                                                                                                Table 1
                                                                                                                                                     Number of moulting individuals among mantis shrimps reared
                                                                                                                                                                             September 1981-December 1982.


                                                                                                                                                                                                         Month


                                                                                                                                                                  S 0 N D J F M A M J J A S 0 N D


                                                                                                                                                     lFemale 2 11 0 0 0 0 0 0 0 0 0 3                                                 6 5 0 0
                                                     Group III                              A       .4                                               Male         3 13 0 0 0 0 0 0 0 0 0 3                                            8      7 0 0
                                           16-                                                                                                       Total        5 24 0 0 0 0 0 0 0 0 0 6                                           14 12 0 0

                                                     Group  II
                                                                                                                      4
                                                                                            %


                                                     Group  I                               I
                                           12.                                                                                              Figure 11
                                                                                                                      post-                 Seasonal variation in modal length of the shrimp body for each size-
                                                                 pre-moulting                    moulting             i moulting            group. Each mark indicates the mean body length of each cohort shown
                                                                             period---j,4- period P'N                    period
                                                                                                                                                Figure 10. Straight lines indicate the mean values of marks within
                                              J      F M           A M            J         J  A      S      0        N    D                each size-group. In Group 1, mean values are 12.2 cm (pre-moulting)
                                                                                  HOKH                                                      and 13.8 cm (post-moulting); in Group H, 14.0 cm and 15.6 cm; and
                                                                                                                                            in Group H1, 15.9 cm and 16.6 cm, respectively.

                                                                                                                                          94









                                                  Table 2                                                                                                       Moulting
                              Values of constant (a) in length-weight regression
                              equation, W       aL'-', of the mantis shrimps                                  60                              Spawning
                                                    reared.
                                                                                                                    Group III
                              Date                  Female                  Male


                              2 Nov                 -1.935                  -1.925
                              16 Dec                -1.946                  -1.938
                              5 Jan                 -1.940                  -1.923
                                                                                                           .T       Group II
                              2 Mar                 -1.942                  -1.917                          ;40
                                                                                                                                                              >2
                              6 May                 -1.934                  -1.924                                6- 0
                                                                                                                                                  0---
                              9 June                -1.915                  -1.933
                              10 July               -1.955                  -1.938                         co
                              17 Aug                -1.951                  -1.929
                              6 Sept                -1.935                  -1.944                                   Group I
                                                    -1.956                  -1.943
                              5 Oct
                              4 Nov                 -1.947                  -1.944
                              4 Dec                 -1.964                  -1.954                            20


                                                                                                                  1)         F         A         J          A          0          0
                                                                                                                                            M a n t h


                                                                                                                                         Figure 12
                                                                                                         Seasonal change in body weight calculated by substituting the length-
                                                                                                         weight regression models shown in Table 2 for the body length derived
                                                                                                         from the equation L.,j = 0.755L. + 4.743, starting with 12.2 cm.
                                                                                                         Circles indicate female weight and triangles indicate male. Values at
                                                                                                         spawning and moulting are shown at 15 June and 15 September with
                                                                                                                                         open marks.





                                                                                              Table 3
                 Changes in dry weight of muscle, hepatopancreas, integument, exuviae, gonad, and spawn of mantis shrimp. Values of body length are derived
                 from the equation, L,+, = 0.7551, + 4.743, starting from 12.2 cm. Values of body weight are derived from body lengths and values of a from
                 the equation, W = aV-' (table 2). Values of each body component are derived from body weight and the regression equations of body weight-
                                                                                      dry component weight.

                                                                                                                        Dry weight (g)
                                                      Body weight
                                          Body               (g)                                       Female                                                   Male
                  Size                    length
                 group        Date        (cm)      Female       Male       Muscle     Hepat.      Integ.     Exu.     Gonad       Spawn       Muscle     Hepat.       Integ.     Exu.

                              12 Dec      12.2        24.4       24.9       1.98        0.27       2.77       0.00      0.18        0.00        2.02        0.20       3.16       0.00
                              9 Feb                   24.7       25.9       2.00        0.19       2.81       0.00      0.10        0.00        2.11        0.22       3.27       0.00
                              11 Apr                  24.9       25.8       2.02        0.25       2.83       0.00      0.15        0.00        2.10        0.21       3.26       0.00
                              9 June                  26.2       25.1       2.14        0.17       2.96       0.00      0.87        0.00        2.04        0.21       3.18       0.00
                    1         15 June                 23.6                  1.90        0.15       2.69       0.00      0.05        1.10
                              10 Aug                  24.1       25.2       1.95        0.12       2.74       0.00      0.07        0.00        2.05        0.21       3.19       0.00
                              6 Sept                  25.0       24.5       2.03        0.21       2.84       0.00      0.04        0.00        1.99        0.20       3.11       0.00
                              15 Sept     14.0        34.4       37.4       2.89        0,33       1.59       1.85      0.07        0.00        3.17        0.36       1.71       2.00
                              13 Oct                  36.5       37.4       3.09        0.23       4.04       0.00      0.05        0.00        3.17        0.36       4.61       0.00
                              22 Dec                  36.8       38.0       3.11        0.48       4.07       0.00      0.39        0.00        3.23        0.37       4.68       0.00


                              12 Dec      14.0        37.3       38.0       3.16        0.49       4.12       0.00      0.40        0.00        3.23        0.37       4.68       0.00
                              9 Feb                   37.6       39.5       3.19        0.34       4.15       0.00      0.23        0.00        3.37        0.39       4.85       0.00
                              11 Apr                  37.9       39.3       3.22        0.45       4.18       0.00      0.32        0.00        3.35        0.39       4.83       0.00
                              9 June                  39.9       38.3       3.41        0.32       4.39       0.00      1.92        0.00        3.26        0.37       4.72       0.00
                   11         15 June                 36.1                  3.04        0.27       3.99       0.00      0.11        1.70
                              10 Aug                  36.7       38.6       3.11        0.22       4.06       0.00      0.16        0.00        3.28        0.38       4.75       0.00
                              6 Sept                  38.1       37.4       3.24        0.39       4.20       0.00      0.09        0.00        3.17        0.36       4.61       0.00
                              15 Sept     15.3        45.1       49.0       3.90        0.49       2.04       2.41      0.12        0.00        4.28        0.53       2.20       2.62
                              13 Oct                  48.0       49.1       4.18        0.34       5.21       0.00      0.08        0.00        4.29        0.53       5.94       0.00
                              22 Dec                  48.3       49.9       4.21        0.71       5.24       0.00      0.65        0.00        4.36        0.54       6.03       0.00


                                                                                                   95








                                                                                         Table 3 (contintied)

                                                                                                                             Dry weight (g)
                                                           Body weight
                                               Body             (9)                                        Female                                                    Male
                       Size                    length
                      group       Date         (cm)      Female      Male      Muscle      Hepat.      Integ.     Exu.    Gonad       Spawn      Muscle        Hepat.     Integ.    Exu.

                                  12 Dec       15.3        48.9      49.8       4.27        0.72       5.30       0.00       0.66      0.00        4.35        0.54       6.02      0.00
                                  9 Feb                    49.3      51.9       4.31        0.50       5.34       0.00       0.38      0.00        4.56        0.57       6.26      0.00
                                  11 Apr                   49.8      51.6       4.35        0.67       5.39       0.00       0.54      0.00        4.53        0.57       6.23      0.00
                                  9 June                   52.4      50.3       4.61        0.46       5.65       0.00       3.19      0.00        4.40        0.55       6.08      0.00
                        111       15 June                  47.3                 4.11        0.40       5.14       0.00       0.18      2.26
                                  10 Aug                   48.2      50.6       4.20        0.33       5.23       0.00       0.27      0.00        4.43        0.55       6.11      0.00
                                  6 Sept                   50.1      49.0       4.38        0.57       5.42       0.00       0.15      0.00        4.28        0.53       5.93      0.00
                                  15 Sept      16.3        54.8      59.6       4.84        0.65       2.45       2.92       0.10      0.00        5.31        0.70       2.65      3.18
                                  13 Oct                   58.2      59.7       5.17        0.44       6.24       0.00       0.11      0.00        5.32        0.70       7.13      0.00
                                  22 Dec                   58.7      60.6       5.22        0.94       6.29       0.00       0.93      0.00        5.41        0.71       7.23      0.00




                                                                                                                                              Table 4
                                                                                                             Daily amounts of feeding and assimilation efficiencies in each size
                    Food consumption                                                                                                 group of mantis shrimp.
                    Food consumption of mantis shrimp was reported by Yama-                                                          Food        Feces         Food         Assimilation
                    zaki (1985) and is summarized as follows.                                                     Size               eaten     excreted    assimilated       efficiency
                       Daily amounts of food eaten and feces excreted by the                                 group       Month       - - - - (mg dry weight) - - - -            (%)
                    shrimp were measured during a period of about one year,                                              Dec         52.15       4.99          47.16            90.4
                    December 1981-December 1982. Because crustaceans often                                               Jan         33.50       11.05         22.45            67.0
                    appear in stomachs of wild shrimp, euphausids were used                                              Feb         69.48       6.51          62.97            90.6
                    for food. Daily feeding rates are high August-October and                                            Mar         91.60       13.20         78.40            85.6
                                                                                                                         Apr         102.76      6.78          95.98            93.4
                    are about five times as high as the lowest value January-                                            May         139.09      16.38         122.71           88.2
                    March (Table 4). However, assimilation efficiencies are at                                    11     June        116.08      5.32          110.76           95.4
                    the level of about 90% in almost all months.                                                         July        237.64      10.58         227.06           95.5
                                                                                                                         Aug         269.71      13.05         256.66           95.2
                                                                                                                         Sept        204.86      8.63          196.23           95.8
                    Bioenergetics                                                                                        Oct         147.51      13.50         134.01           90.8
                                                                                                                         Nov         134.64      26.58         108.06           80.3
                    The process of individual production may be described using                                          Dec         90.19       6.09          84.10            93.2
                    the following equation:                                                                              Dec         57.96       3.42          54.54            94.1
                                                                                                                         Jan         40.12       1.88          38.24            95.3
                                           G + R = A = C - E                                                             Feb         26.32       0.56          25.76            97.9
                                                                                                                         Mar         120.20      8.55          111.65           92.9
                    where G = growth, R = metabolic loss, A = assimilation,                                              Apr         138.06      8.82          129.24           93.6
                    C = consumption, and E = egestion. Values of each param-                                             May         158.65      14.06         144.59           91.1
                                                                                                                  11     June        197.46      3.09          194.37           98.4
                    eter were calculated in the following manner:                                                        July        224.15      11.69         212.46           94.8
                                                                                                                         Aug         226.71      7.82          218.89           96.6
                    Growth is presented as the amount of accumulated energy                                              Sept        214.63      12.98         201.65           94.0
                    during rearing periods. The amounts of energy of each body                                           Oct         313.72      26.38         287.34           91.6
                    component were obtained by bimonthly weight determina-                                               Nov         272.81      21.54         251.27           92.1
                    tions of body components listed in Table 3 and their caloric                                         Dec         88.19       3.15          85.04            96.4
                    values determined with a bomb calorie meter (Table 5), and                                           Dec         55.15       2.50          52.65            95.5
                    the accumulated energy was obtained from the differences                                             Jan         25.24       1.70          23.54            93.3
                                                                                                                         Feb         21.06       10.02         11.04            52.4
                    between these bimonthly determinations shown with the                                                Mar         54.65       9.98          44.67            81.7
                    caloric unit (Table 6).                                                                              Apr         128.90      20.34         108.56           84.2
                      The muscle achieves a large accumulation of energy at                                              May         171.11      8.52          162.59           95.0
                    moulting. Due to moulting, the integument also shows a rapid                                  Ell    June        190.17      10.69         179.48           94.4
                    accumulation and consumption of energy during September                                              July        232.78      16.94         215.84           92.7
                                                                                                                         Aug         365.99      34.78         331.21           90.5
                    and October. In females, there is a large accumulation and                                           Sept        229.21      16.96         212.25           92.6
                    consumption of energy before and after spawning.                                                     Oct         176.22      17.87         158.35           89.9
                                                                                                                         Nov         151.00      5.37          145.27           96.2
                                                                                                                         Dec         44.18       3.94          40.34            91.3

                                                                                                       96









                                                                                              TAble 5
                        Changes in energy values of muscle, hepatopancreas, integument, exuviae, gonad, and spawn of mantis shrimp. See Table 3.

                                                                                                                       Energy value (kcal)
                                                     Body weight
                                          Body              (9)                                      Female                                                    Male
                 Size                     length
                group        Date         (cm)      Female      Male      Muscle      Hepat.      Integ.     Exu.      Gonad      Spawn        Muscle      Hepat.    Integ.     Exu.

                             12 Dec       12.2       24.4       24.9        8.77       1.50          4.52    0.00      0.94        0.00        8.95        1.11       5.15      0.00
                             9 Feb                   24.7       25.9        8.86       1.06          4.58    0.00      0.52        0.00        9.35        1.22       5.33      0.00
                             11 Apr                  24.9       25.8        8.95       1.39          4.61    0.00      0.78        0.00        9.30        1.17       5.31      0.00
                             9 June                  26.2       25.1        9.48       0.95          4.82    0.00      4.55        0.00        9.04        1.17       5.18      0.00
                   1         15 June                 23.6                   8.42       0.83          4.38    0.00      0.26        6.17
                             10 Aug                  24.1       25.2        8.64       0.67          4.47    0.00      0.37        0.00        9.08        1.17       5.20      0.00
                             6 Sept                  25.0       24.5        8.99       1.17          4.63    0.00      0.21        0.00        8.82        1.11       5.07      0.00
                             15 Sept      14.0       34.4       37.4      12.80        1.83          2.59    3.02      0.37        0.00        14.04       2.00       2.79      3.26
                             13 Oct                  36.5       37.4      13.69        1.28          6.59    0.00      0.26        0.00        14.04       2.00       7.51      0.00
                             22 Dec                  36.8       38.0      13.78        2.67          6.63    0.00      2.04        0.00        14.31       2.06       7.63      0.00


                             12 Dec       14.0       37.3       38.0      14.00        2.72          6.72    0.00      2.09        0.00        14.31       2.06       7.63      0.00
                             9 Feb                   37.6       39.5      14.13        1.89          6.76    0.00      1.20        0.00        14.93       2.17       7.91      0.00
                             11 Apr                  37.9       39.3      14.26        2.50          6.81    0.00      1.67        0.00        14.84       2.17       7.87      0.00
                             9 June                  39.9       38.3      15.11        1.78          7.16    0.00      10.04       0.00        14.44       2.06       7.69      0.00
                  11         15 June                 36.1                 13.47        1.50          6.50    0.00      0.58        9.54
                             10 Aug                  36.7       38.6      13.78        1.22          6.62    0.00      0.84        0.00        14.53       2.11       7.74      0.00
                             6 Sept                  38.1       37.4      14.35        2.17          6.85    0.00      0.47        0.00        14.04       2.00       7.51      0.00
                             15  Sept     15.3       45.1       49.0      17.28        2.72          3.33    3.93      0.63        0.00        18.96       2.95       3.59      4.27
                             13 Oct                  48.0       49.1      18.52        1.89          8.49    0.00      0.42        0.00        19.00       2.95       9.68      0.00
                             22 Dec                  48.3       49.9      1&65         3.95          8.54    0.00      3.40        0.00        19.31       3.00       9.83      0.00


                             12 Dec       15.3       48.9       49.8      18.92        4.00          8.64    0.00      3.45        0.00        19.27       3.00       9.81      0.00
                             9 Feb                   49.3       51.9      19.09        2.78          8.70    0.00      1.99        0.00        20.20       3.17      10.20      0.00
                             11 Apr                  49.8       51.6      19.27        3.73          8.79    0.00      2.82        0.00        20.07       3.17      10.15      0.00
                             9 June                  52.4       50.3      20.42        2.56          9.21    0.00      16.68       0.00        19.49       3.06       9.91      0.00
                  111        15 June                 47.3                 18.21        2.22          8.38    0.00      0.94       12.69
                             10 Aug                  48.2       50.6      18.61        1.83          8.52    0.00      1.41        0.00        19.62       3.06       9.96      0.00
                             6 Sept                  50.1       49.0      19.40        3.17          8.83    0.00      0.79        0.00        19.96       2.95       9.67      0.00
                             15 Sept      16.3       54.8       59.6      21.44        3.61          3.99    4.76      0.52        0.00        23.52       3.89       4.32      5.18
                             13 Oct                  58.2       59.7      22.90        2.45       10.17      0.00      0.58        0.00        23.57       3.99      11.62      0.00
                             22 Dec                  58.7       60.6      23.12        5.23       10.25      0.00      4.86        0.00        23.97       3.95      11.78      0.00






                                                                                              Table 6
                                                     Amount of absolute growth derived from Table 5, expressed in kilocalories.

                             Duration of                                    Female                                                    Male                               Total
                 Size          rearing
                group          (days)           Muscle      Hepat.      Integ.    Exu.        Gonad      Spawn         Muscle    Hepat.        Integ.   Exu.      Female      Male

                             59 (Dec-Feb)         0.09      -0.44         0.06    0.00        -0.42       0.00         0.40        0.11        0.18     0.00       -0.71        0.69
                             61 (Feb-Apr)         0.09        0.33        0.03    0.00          0.26      0.00         -0.05      -0.05        -0.02    0.00        0.71      -0.12
                             59 (Apr-June)        0.53      -0.44         0.21    0.00          3.77      0.00         -0.26       0.00        -0.13    0.00        4.07      -0.39
                             6 (June-June)       -1.06      -0.12       -0.44     0.00        -4.29       6.17         0.04        0.00        0.02     0.00        0.26        0.06
                  1          56 (June-Aug)        0.22      -0.16         0.09    0.00          0.11      0.00                                                      0.26
                             27 (Aug-Sept)        0.35        0.50        0.16    0.00        -0.16       0.00         -0.26      -0.06        -0.13    0.00        0.85      -0.45
                             9 (Sept-Sept)        3.81        0.66      -2.04     3.02          0.16      0.00         5.22        0.89        -2.28    3.26        5.61        7.09
                             28 (Sept-Oct)        0.89      -0.55         4.00    0.00        -0.11       0.00         0.00        0.00        4.72     0.00        4.23        4.72
                             70 (Oct-Dec)         0.09        1.39        0.04    0.00          1.78      0.00         0.27        0.06        0.12     0.00        3.30        0.45









                                                                                                97








                                                                                             Table 6 (continued)

                                     Duration of                                     Female                                                     Male                               Total
                         Size          rearing
                        group           (days)           Muscle     Hepat.      Integ.      Exu.       Gonad        Spawn      Muscle      Repat.     Integ.      Exu.         Female   Male

                                  59 (Dec-Feb)             0.13     -0.83         0.04      0.00        -0.89       0.00         0.62        0.11        0.28     0.00         -1.55      1.01
                                  61 (Feb-Apr)             0.13        0.61       0.05      0.00         0.47       0.00       -0.09         0.00     -0.04       0.00         1.26     -0.13
                                  59 (Apr-June)            0.85     -0.72         0.35      0.00         8.37       0.00       -0.40       -0.11      -0.18       0.00         8.85     -0.69
                                     6 (June-June)       -1.64      -0.28       -0.66       0.00        -9.46       9.54         0.09        0.05        0.05     0.00         -2.50      0.19
                          11      56 (June-Aug)            0.31     -0.28         0.12      0.00         0.26       0.00                                                       0.41
                                  27   (Aug-Sept)          0.57        0.95       0.23      0.00        -0.37       0.00       -0.49       -0.11      -0.23       0.00         1.38     -0.83
                                     9 (Sept-Sept)         2.93        0.55     -3.52       3.93         0.16       0.00         4.92        0.95     -3.92       4.27         4.05       6.22
                                  28 (Sept-Oct)            1.24     -0.83         5.16      0.00        -0.21       10.00        0.04        0.00        6.09     0.00         5.36       6.13
                                  70 (Oct-Dec)             0.13        2.06       0.05      0.00         2.98       0.00         0.31        0.05        0.15     0.00         5.22       0.51

                                  59 (Dec-Feb)             0.17     -1.22         0.06      0.00        -1.46       0.00         0.93        0.17        0.39     0.00         -2.45      1.49
                                  61 (Feb-Apr)             0.18        0.95       0.09      0.00         0.83       0.00       -0.13         0.00     -0.05       0.00         2.05     -0.18
                                  59 (Apr-June)            1.15     -1.17         0.42      0.00        13.86       0.00       -0.58       -0.11      -0.24       0.00         14.26    -0.93
                                     6 (June-June)       -2.21      -0.34       -0.83       0.00       -15.74       12.68      _0.13         0.00        0.05     0.00         -6.44      0.18
                         111      56 (June-Aug)            0.40     -0.39         0.14      0.00         0.47       0.00                                                       0.62
                                  27 (Aug-Sept)            0.79        1.34       0.31      0.00        -0.63       0.00         0.66      -0.11      -0.29       0.00         1.81     -1.06
                                     9 (Sept-Sept)         2.04        0.44     -4.84       4.76        -0.26       0.00         3.56        0.94     -5.35       5.18         2.14       4.33
                                  28 (Sept-Oct)            1.46     -1.16         6.18      0.00         0.06       0.00         0.05        0.00        .7.30    0.00         6.54       7.35
                                  70 (Oct-Dec)             0.22        2.78       0.08      0.00         4.28       0.00         0.40        0.06        0.16     0.00         7.36       0.62





                     Metabolic loss The amount of oxygen consumption in each
                     individual housed in a plastic chamber was measured by the                                              5-     log R     log(O.0523 t        0. 0415) + 0.2881 IogW
                     Winkler method for 7-9 shrimp of various sizes. A regres-
                     sion equation among oxygen consumption per unit time,
                     water temperature, and body weight was obtained (Fig. 13).
                     From this equation and monthly mean values of body weight
                                                                                                                    4@
                     and water temperature, monthly oxygen consumptions were                                                                                           A
                     calculated. The standard metabolism in terms of caloric value                                                                                             8
                     was determined by multiplying the oxygen consumption by                                                                 A
                                                                                                                    0     1            A
                                                                                                                                                              _0
                     4.83 cal/niL-02 (IvIev 1934).                                                                  co    0                                         0
                                                                                                                    ;@    -           4
                                                                                                                    1-1                          A
                         The amount of metabolic loss was assumed as twice the                                      P.
                                                                                                                    to
                                                                                                                    (D
                     standard metabolism from the                 literature (McLeese 1964,
                     McFarland and Pickens 1965, Nelson et al. 1977a,b, Logan                                                                                          -50
                     and Epifanio 1978) in which specific dynamic action and                                                                   Body weight             g:wet
                     swimming were considered (Table 7).
                        The amounts of energy released for metabolic activity are                                                                 Figure 13
                     in the range of 0.46-0.76 kcal-day-l-ind-I during June                                     Logarithmic plots of respiratory rate against body weight. 0 9.0*C;
                                                                                                                0 11.5*C; A 15.0'C; A 19.2*C. The base of logarithms in this equa-
                     and October, and are under 0.4 kcal - day-' - ind- I during                                                                  tion is 10.
                     the winter period of inactive feeding, unrelated to differences
                     in body size or sex.

                     Assimilation The equation for the amount of assimilation                                   of assimilation divided by these efficiencies gave the bi-
                     was G + R = A (Table 6).                                                                   monthly values of consumption (Table 7).
                                                                                                                    Seasonal variations of ingestion energy shown in Table 7
                     Consumption In this paper, food consumption is calculated                                  generally have the same tendencies as that of the daily
                     by A/assimilation effeciency. From the monthly values of                                   arnounts of food eaten shown in Table 4.
                     daily ingestion the daily defecation rates obtained with the
                     units of weight in Table 4 and the caloric values of euphau-
                     sids (6.05 kcal-g dry wt-1) and defecations (5.09 kcal-g
                     dry wt-1), the assimilation efficiency was calculated in
                     terms of caloric value (Table 8). Further, the monthly values


                                                                                                           98









                                                                                              Table 7
                                                          Food energy distribution in mantis shrimp, expressed in kitocalories.

                                                       Metabolic   loss           Total growth            Assimilation energy               Ingestion                  Egestion
                                 Duration of                 (R)                        (G)                        (A)                        (C)                       (E)
                                   rearing
                 Group             (days)             Female       Male          Female       Male           Female      Male          Female        Male        Female        Male

                              59   (Dec-Feb)          17.40        17.56         -0.71          O@69         16.69       18.25         20.45         22.37          3.76       4.12
                              61   (Feb-Apr)          17.10        17.30          0.71        -0.12          17,81       17.18         19.70         19.00          1.89       1.82
                              59 (Apr-June)           22.78        22.78          4.07        -0.39          26.85       22.39         29.06         24.23          2.21       1.84
                                 6 (June-June)         2.78        33.10          0.26          0.06           3.04      33.16         34.48         34.51          1.34       1.35
                    1         56 (June-Aug)           29.84                       0.26                       30.10
                              27 (Aug-Sept)           16.22        16.30          0.85        -0.45          17.07       15.85         17.76         16.49          0.69       0.64
                                 9 (Sept-Sept)         5.58          5.64         5.61          7.09         11.19       12.73         11.60         13.19          0.41       0.46
                              28   (Sept-Oct)         17.18        17.40          4.23          4.72         21.41       22.12         22.63         23.38          1.22       1.26
                              70 (Oct-Dec)            34.04        34.30          3.30          0.45         37.34       34.75         41.91         39.11          4.57       4.36

                              59 (Dec-Feb)            19.66        19.86         -1.55          1.01         18.11       20.87         18.86         21.74          0.75       0.87
                              61   (Feb-Apr)          19.30        19.52          1.26        -0.13          20.56       19.39         21.55         20.32          0.99       0.93
                              59 (Apr-June)           25.74        25.72          8.85        -0.69          34.59       25.03         36.76         26.60          2.17       1.57
                                 6 (June-June)         3.14        37.38         -2.50          0.19           0.64      37.57         35.86         38.77          1.11       1.20
                    H         56 (June-Aug)           33.70                       0.41                       34.11
                              27 (Aug-Sept)           18.32        18.42          1.38        -0.83          19.70       17.59         20.39         18.21          0.69       0.62
                                 9 (Sept-Sept)         6.14          6.22         4.05          6.22         10.19       12.44         10.73         13.09          0.54       0.65
                              28   (Sept-Oct)         18.60        18.88          5.36          6.13         23.96       25.01         25.49         26.61          1.63       1.60
                              70 (Oct-Dec)            36.82        37.10          5.22          0.51         42.04       37.61         44.53         39.84          2.49       2.23

                              59 (Dec-Feb)            21.24        21.46         -2.45          1.49         18.79       22.95         20.95         25.59          2.16       2.64
                              61   (Feb-Apr)          20.88        21.12          2.05        -0.18          22.93       20.94         29.66         27.09          6.73       6.15
                              59   (Apr-June)         27.86        27.80         14.26        -0.93          42.12       26.87         45.39         32.19          3.27       5.32
                                 6 (June-June)         3.40        46.42         -6.44          0.18         -3.04       40.60         36.13         43.15          2.13       2.55
                   in         56 (June-Aug)           36.42                       0.62                       37.04
                              27 (Aug-Sept)           19.82        19.90          1.81        -1.06          21.63       18.84         23.41         20.39          1.78       1.55
                                 9 (Sept-Sept)         6.58          6.64         2.14          4.33           8.72      10.97           9.30        11.70          0.58       0.73
                              28   (Sept-Oct)         19.68        19.96          6.54          7.35         26.22       27.31         28.28         29.46          2.06       2.15
                              70 (Oct-Dec)            38.94        39.26          7.36          0.62         46.30       39.88         49.20         42.38          2.90       2.50




                                                 Table 8                                               Egestion The equation for the amount of egestion was
                             Assimilation efficiencies (%) of mantis shrimp                            C - A = E (Table 7). Tables 6 and 7 present the seasonal
                             size groups calculated in terms of caloric value.                         variations of energy budgets per about a two-month period
                                                                                                       in terms of consumption, assimilation, accumulation, and
                                                         Size group                                    egestion of energy. In the sum of these values, the energy
                             Month              I             II              III                      budgets for the year are shown in Table 9.
                                                                                                         In adult shrimp, a total of 190-240 kcal per year are
                              Dec             91.9           95.0           96.2                       ingested and about 90% is assimilated. Almost all the
                              Jan             72.2           96.0           94.4                       assimilated energy is lost by metabolism, and the remaining
                              Feb             92.1           98.2           60.0                       energy (19-26 kcal in females, about 12 kcal in males) is
                              Mar             87.9           94.0           84.6
                              Apr             94.4           94.6           86.7                       accumulated in each body component, of which 7-14 kcal
                              May             90.1           92.5           95.8                       is used for growth of the ovary and 85-90% is released from
                              June            96.1           98.7           95.3                       the body as reproductive substances at spawning. Gross
                              July            96.2           95.6           93.9                       growth efficiencies are indicated 9-11 % in females and 5--6%
                              Aug             96.0           97.1           92.0                       in males.
                              Sept            96.5           95.0           93.8
                              Oct             92.3           92.9           91.5                         Further, if quantitative changes in growth and food con-
                              Nov             83.4           93.4           96.8                       sumption of larva and young are investigated on the basis
                              Dec             94.3           97.0           92.7                       of the above methods, the life history of mantis shrimp will
                                                                                                       be clarified.






                                                                                                  99









                                                                                                        Table 9
                                                                                     Energy budget in the mantis shrimp.

                                                                                          Group I                   Group H                    Group M

                                                         (Kcal/year)                Female         Male        Female         Male        Female         Male


                                                         Food
                                                            Food ingested           197.59         192.28      214. 17       205.18       242.32         231.95
                                                            Feces excreted           16.09         15.85          10.27         9.67        21.61         23.59
                                                            Food assimilated        181.50         176.43      203.91)        195.51      220.71         208.36
                                                            Metabolic loss          162.92         164.38      181.42         183.10      194.82         196.56
                                                         Growth
                                                            Total                    18.58         12.05          2248         12.41        25.89         11.80
                                                            Muscle                    5.01          5.36          4.6.5         5.00         4.20          3.70
                                                            Hepatopancreas            1.17          0.95          1.23          0.94         1.23          0.95
                                                            Integument                2.11          2.48          1.82          2.20         1.61           1.97
                                                            Exuviae                   3.02          3.26          3.93          4.27         4.76          5.18
                                                            Gonad                     1.10          -             1.31          -            1.41          -
                                                            Gametes ejected           6.17          -             9.5.4         -            12.68         -




                    Citations

                    Harding, J.P.
                         1949 The use of probability paper for the graphical analysis of poly-
                            modal frequency distributions. J. Mar. Biol. Assoc. U.K. 28:
                            141-153.
                    Hiatt, R.W.
                         1948 The biology of the lined shore crab, P"hygrapsus awsipes Ran-
                            dall. Pac. Sci. 2:135-213.
                    Iviev, V.S.
                         1934 Eine mikromethode zur bestimming des kaloriengehalts non
                            nalustoffen. Biochem. Zool. 275:49-55.
                    Kurata, H.
                         1960 Increase in size at moulting in Crustacea. Bull. Hokkaido Reg.
                            Fish. Res. Lab. 22:1-48.
                    Logan, D.T., and C.E. Epifanio
                         1978 A laboratory energy balance for the larvae and juveniles of the
                            American lobster Homants americanus. Mar. Biol. 47:381-389.
                    McFarland, W.N., and P.E. Pickens
                         1965 The effects of season, temperature, and salinity on standard and
                            active oxygen consumption of the grass shrimp, Palaentonetes vulgaris
                            (Say). Can. J. Zool. 43:571-585.
                    McLeese, D.W.
                         1964 Oxygen consumption of the lobster, Honwrus anwricanus Milne-
                            Edwards. Helgol. Wiss. Meeresunters. 10:7-18.
                    Nelson, S.G., A.W. Knight, and H.W. Li
                         1977a The metabolic cost of food utilization and ammonia produc-
                            tion by juvenile Macrobrachium rosenbergii (Crustaces:Palaemoni-
                            dae). Comp. Biochem. Physiol. 57A:67-72.
                    Nelson, S.G., H.W. Li, and A.W. Knight
                         1977b Calories, carbon and nitrogen metabolism of juvenile Macro-
                            brachium rosenbergii (De Haan) (Crustacea, Palaemonidae) with
                            regard to tropic position. Comp.Biochem.Physiol.58A:319-327.
                    Yamazaki, M.
                         1985 Food consumption of the mantis shrimp, Oratosquilla oratoria
                            (De Haan). Bull. Fac. Fish. Hokkaido Univ. 36:177-181.
                    Yamazaki, M., and A. Fuji
                         1980 Reproductive cycle of the mantis shrimp, Squilla oratolia de
                            Haan, in Mutsu Bay. Bull. Fac. Fish. Hokkaido Univ. 31:161-168.






                                                                                                         100






            Growth and Survival                                                    Abalone is a major fishery of rocky coastal Japan, priced
                                                                                   at about 5000 yen/kg. Annual catches from 1975 to 1984
            of Artificial Abalone                                                  were between 3900 and 5650 tons. Total world catch in 1982
                                                                                   was approximately 20,000 tons. Japanese consumption of
            Seed Released in                                                       abalones is estimated at about 9000 tons. Japan leads in
                      0                                                            abalone consumption and is the second leading producer,
            Swjfld Bay, Japan                                                      after Australia (Uki 1985). The catch in Japan consists
                                                                                   primarily of four species: Haliotis discus hannai occurs in
                                                                                   the north, while the other species, H. discus, H. gigantea,
                                                                                   and H. sieboldii, range from the central to the southern
            KIYOKAZU INOUE                                                         regions. Propagation of abalones through fishery manage-
            Seikai National Fisheries Research Institute                           ment and protective breeding has had a long history in Japan.
            49 Kokuburnachi                                                        Recently, sea farming techniques of releasing hatchery seed
            Nagasaki 850, Japan                                                    have been developed. The number released in 1983 amounted
                                                                                   to 17.5 million, composed of 64 % H. discus hannai and 34 %
                                                                                   H. discus. The shell length of seeds at release was approx-
                                                                                   imately 30 mm.
            ABSTRACT                                                                  In many cases, however, it is not clear whether the re-
                                                                                   leasing of seeds results in increased catch. The growth rate
            The growth rate and survival rate of artificially produced young       and survival rate of artificially produced young abalone,
            abalone, Haliods discus, on the fishing ground was determined          H. discus, on the fishing ground was determined in order
            in order to develop a method for evaluating its ecological and         to develop a method for evaluating its ecological and bio-
            biological characteristics. Daily growth (pm/day) decreased dur-       logical characteristics.
            ing the period with the high water temperature. The mean daily
            growth differed between the two stations. Survival rates de-
            creased throughout the experiment, and the largest decrease
            occurred just after release.                                           Materials and methods

                                                                                   Two experimental stations, A and B, were located in Skijiki
                                                                                   Bay, Hirado island, in southern Japan (Fig. 1). The dura-
                                                                                   tion of the experiment was 20 March-25 September 1986.



                                                                                                                                130*E      132@E


                                                                                                                         Hirad 0                34! N
                                                                                                                           Is.

                                                                                                                                   Kyushu
                                                                                               St. B                                             IfN


                                                                                                         St. A








                                                                                            0         1km
                                                                                                                            ff

                                                                                                                            '00
                                                                                                                            I've-


                                                                                                              Figure 1
                                                                                     Location of experimental stations, Shoiki Bay, southern Japan.



                                                                              101







                        20-                                      GROUP Y                          150


                        10-                                   ALL
                                                                                                                                 ST. A
                                                                                                                                   0-0 GROUP Y

                        0                                                                                                          *-* GROUP M
                                                                                              1:- 100-
                                                                                                                                 ST. B
                        20-                                                                   3-                                           GROUP M


                                                              RECAPTURED
                        10-                                                                   cc



                   z
                   LU   0                                                                         50-


                        20-
                   cc                                            GROUP     M
                   U_

                        10-                                   ALL
                                                                                                   0
                                                                                                                                                     0

                        0                                                                               M       A      M       i      i       A      S
                                                                                                      1986
                        20-

                        10-                                   RECAPTURED                                               Figure 3
                                                                                                    Seasonal changes in daffy growth of abalone seed.



                             25                    35                    45
                                     SHELL LENGTH (mm)                                     September. Samples were collected by two or three SCUBA
                                                                                           divers for two hours each time. Color and number of the
                                             Figure 2                                      tags, shell length and body weight were determined. Mea-
                 Distribution of shell length of abalone seed at release and recapture.    sured abalones were taken to their former station and released
                                                                                           carefully, but randomly, in order to obtain an accurate
                                                                                           analysis.
                                                                                             Growth rate was indicated as daily growth (Am/day),
                 Station A was a pile of stones surrounded by sand at a depth              calculated by dividing the increase of shell length by the days
                 of about 7 meters. It had some sargassurn and other small                 between release and recapture. This calculation used only
                 seaweeds. The sargassum decreased after July, in the typical              the data of individuals recaptured in consecutive samplings.
                 seasonal pattern. Some natural juvenile abalones lived in                 Survival rate was calculated from the total number released
                 Station A. The area of the rock pile was about 150 m2 and                 initially and the total number in the population estimated at
                 the height was about 1.5 m. Station A was selected because                each sampling. Total number in the population was estimated
                 the surrounding sand would prevent dispersion of the planted              by Jolly-Seber's multiple recapture method.
                 abalones. Station B was on a rocky coast with much seaweed
                 at a depth of 1-5 meters. The seawood was mostly sea oak,
                 Eisenia bicyclis. Station B was considered a suitable envi-               Results
                 ronment for abalones and was selected to compare its growth
                 rate with Station A.                                                      The numbers of abalone recaptured at Station A were 217
                   The abalones, all H. discus, used in this study were ob-                on 23 April, 156 on 27 May, 44 on 22 August, and 20 on
                 tained from Yamaguchi Prefecture (Group Y) and Miyagi                     25 September. Distribution of shell length of all individuals
                 Prefecture (Group M). Initial mean shell lengths were 31.5                measured at initial release was compared with that of the
                 mm and 29.2 nun, respectively. The numbers released at                    recaptured individuals for groups Y and M (Fig. 2). In Group
                 Station A were 996 of Group Y and 985 of Group M. Num-                    Y, both distributions are similar; however, in Group M, in
                 bers released at Station B were 75 of Group Y and 315 of                  the; distribution of recaptured individuals, the smallest ones
                 Group M. Individuals were distinguished by the color and                  were virtually absent.
                 number of a tag attached to the shell by adhesive.
                   Seeds were released by SCUBA divers on 20 March and
                 sampled four times: 23 April, 27 May, 22 August, and 25

                                                                                     102









                                                                                    Table 1
                                                 Population of artificial abalone, H. discus, estimated by Jolly-Seber process.

                                                                                                         No. recaptured
               Time at release (i)             No. captured          No. released                                                             Estimated population
               Time at recapture (j)                 ni                    Si                 i=l          2           3           4                    Ni


                           1                        1981                   1981               -                                                         -
                           2                         212                    208               212                                                       755
                           3                         153                    152               110         43                                            552
                           4                           42                    42               21           7           14                               210
                           5                           20                    19               10           4            2          4                    -




                       100-                                                                   Discussion
                                                              0-0 GROUP Y
                                                              -GROUP M                        Apparently, artificial seed varies in biological character when
                                                                                              produced by different hatcheries. In this experiment, it was
                                                                                              determined that daily growth and size distribution of recap-
                  LU                                                                          tured individuals differed between groups Y and M. To
                  t@
                  cc    50-                                                                   go ftirther in this field, it will be necessary to study the
                                                                                              relationship between ecological character and production
                  >                                                                           conditions.
                                                                                                The difference in daily growth between the two stations
                                                                                              was experimentally confirmed. Although the growth rate is
                                                                                              known to be altered by living conditions (Uld 1981, Inoue
                         0.
                              M       A       M        i      i       A        S              et al. 1986), the present experiment can be useful as a method
                            1986                                                              for selecting a sea fanning area. For that purpose it is
                                                                                      I       necessary to obtain further data on growth rate and its
                                            F%m 4                                             seasonal variation in young abalone under natural conditions.
                       seasonal changes In survival rate of abalone seed.
                                                                                              Citations


                                                                                              Inoue, K., H. Kito, N. Uki, and S. Kikuchi
                 Daily growth of every group at each station decreased                           1986 Influence of the high temperature on the growth and survival
              throughout the experiment (Fig. 3). Especially during 22                             of three species of abalone. Bull. iekai Reg. Fish. Res. Lab.
                                                                                                   63:73-78.
              August-25 September, the period with the highest water                          Kato, F.
              temperature, there was no sign of increase in shell length                         1978 An HPL (Hewlett-Packard Language) calculator program for
              at Station A. Also, the mean daily growth of Group M at                              capture-recapture stochastic model of G.M. Jolly. Bull. Jpn. Sea
              Station A was always larger than that of Group Y, except                             Reg. Fish. Res. Lab. 29:283-290.
              for the period 22 August-25 September. In comparison,                           Uki, N.
                                                                                                 1981 Food value of marine algae of order larninariales for growth
              Station B had much more daily growth in Group M.                                     of the abalone, HaUofis discus hwuW. Bull. Tohoku Reg. Fish. Res.
                 In the Jolly-Seber model, mhi, number caught in the ith                           Lab. 42:19-29.
              sample last captured in the hth sample, were recorded in                           1985 Recent status of abalone fisheries and studies in the foreign
              Table 1. Total number in the population was calculated from                          shores. Nihon Suisanshigen Hogo Kyokai Geppou 251:5-16.
              that table, estimated by a personal computer program (Kato
              1978).
                 Survival rates of groups Y and M decreased throughout
              the experiment, and the largest decrease occurred just after
              release (Fig. 4).







                                                                                        103






              Copepod Swarms                                                                      In Shijiki Bay, pelagic larvae of red sea bream migrate into
                                                                                                  the Bay from offshore waters during April to May and
              Observed by SCUBA                                                                   become demersal. In the Bay, stomachs of demersal juveniles
                                                                                                  are filled with Acartia omoiii and A. steueri (Tanaka 1985).
              Diving in a Small Inlet                                                             These copepods, important food organisms for fish in a
                                                                                                  neritic society, have swarming characteristics.
              of Kyushu, Japan'                                                                      Copepod swarms have been observed in dense crowds at
                                                                                                  specific spots in the neritic waters of the tropical, subtropical,
                                                                                                  temperate regions, and freshwater lakes of the Arctic as well.
                                                                                                  Many species in the genera 0ithona, Acartia, Centropages,
              KATSUNORI KIMOTO                                                                    and Labidocera appear in swarming communities in neritic
              Seikai National Fisheries Research Institute                                        waters (Emery 1968, Hamner and Carleton 1979, Omori and
              Fisheries Agency                                                                    Hamner 1982). Swarms of Heterocope septentrionalis and
              Kokubu-machi 49                                                                     Diaptomus tyrrelli also occur in freshwater lakes (Hebert
              Nagasaki 850, Japan                                                                 et al. 1980, Byron et al. 1983). Ueda et al. (1983) reported
                                                                                                  swarms of the copepod genera Acartia, Oithona, and Labi-
                                                                                                  docera in the coastal waters of Japan.
                                                                                                     Copepod swarms on the sea bottom must play a major role
              ABSTRACT                                                                            in the food strategy of juveniles of dernersal fishes. In Shijiki
                                                                                                  Bay, copepod swarms were observed fragmentarily in 1978
              Swarms of copepods were observed by SCUBA diving in Shijiki                         and 1980 by Ueda et al. (1983). Therefore, in the Bay, the
              Bay, southwest of Hirado Island, western Kyushu, Japan, dur-                        author has intensely investigated copepod swarms to learn
              ing early spring to midsummer 1984-85. Copepods were densely                        the seasonal changes in distribution, locality, and size of
              distributed just above the sea bottom in the daytime and formed                     swarms in the various areas.
              various features of swarm according to the configuration of sea
              bottom and season. Seven swarming copepod species, Acartia
              ontorii, A. steueyi, A. sinfiensis, Oikhona ocu         , 0, davisae, Tor-
              tanus longipes, and T. rubidus, were identified. Each swarm con-                    Copepod swarms
              sisted of many copepodite stages, sometimes of a single species
              but also of a mixture of several species. Species, stage and sex                    Copepod swarms were observed and collected at Shijiki Bay,
              composition, shape of swarm, and swarming location varied                           southwestern Hirado Island, western Kyushu, Japan, from
              seasonally. The swarm maintained a stationary spatial position                      May to August 1984 and 1985 (Fig. 1). Repeated obser-
              when the water current was weak. Swarming of Acarda and
              0ithona may serve as an important food for some juvenile
              demersal fishes during their early demersal stages.
                                                                                                                                                       130*          132'


                                                                                                                                                                            34*



                                                                                                                                                             Kyushu



                                                                                                                                                                            32*
                                                                                                                          s_8          M.g-ki

                                                                                                                           *S-7


                                                                                                                                *S-2

                                                                                                                                       S-3
                                                                                                                                                     -1          -7
                                                                                                                                          0 S-4    \L      _51 IL
                                                                                                                                                IL-2
                                                                                                                               -10                   %-5 L-3
                                                                                                                               -9        lid.-        S 6  'L-4
                                                                                                                                          b-
                                                                                                                             S-7


                                                                                                                                 S
                                                                                                                                  -2
                                                                                                                                      S@
                                                                                                                                          -S



                                                                                                                                9
                                                                                                                                          b-
                                                                                                                    0    Q5     1 k@



                                                                                                                                  Figure 1
                                                                                                  Location of stations in SMiki Bay, southwest of Hirado L, western Kyu-
                'Contribution No. 439 of the Seikai National Fisheries Research Institute.        shu, Japan. Stations with slanted bar indicate where rope line was set.

                                                                                            105









                                                                                                  Table 1
                                                                    Copepod swarms observed by SCUBA diving in SMiki Bay.

                      Species                                     Shape and size of swarm                             Depth (m)            Swarming location

                      Acartia omorii                              Continuous flat swarm, 5-30 cm thick                   10-27             Over flat sandy bottom
                                                                  Irregular balls, 10-30 cm diameter                     10-24             Over flat sandy and gravelly bottom
                      A. omorli + A. steueri                      Continuous flat swarm, 5-30 cm thick                   10-18             Over flat sandy bottom
                                                                  Irregular balls,  10-50 cm diameter                    10-13             Over flat sandy bottom
                                                                  Irregular balls,  10-50 cm diameter                      7               Over and throughout entire Zostera bed
                                                                  Irregular balls,  10 cm-3 m diameter                     2-7             Over rocky shore, around algal bed
                      A. steued                                   Irregular balls,  10 cm-1 m diameter                     2-7             Over and throughout entire Zostera bed
                      A. steueri  + Oithona davisae               Irregular balls,  30-50 cm diameter                      3               Edge of Zostera bed
                      a oculata                                   Irregular balls,  10-30 cm diameter                      2-7             Inside Zostera bed, over rocky shore and
                                                                                                                                             gravelly bottom
                      0. oculata   + A. sinjiensis                Ball, 10 cm diameter                                     4               Edge of Zostera bed
                      Tortanus longipes + T. rubidus              Column, 20 cm diameter, 50 cm height                     2               Edge of Zostera bed





                          a                                                                               b.
                         Current                          Acartia   omorii                                                 Acartia omorii         Oithona oculata
                                                                                                                                                                          :@ :. Gil I
                                                          Acartia   steueri                                                Acartia steueri 0ithona davisae                ..:
                                                                                                                                                                                net
                                                          Oithona   oculata                                                Acartia siniiensis,                            *t* e*u er 2
                                                                                                                                                                       A.s
                                           5-3
                                              Ocm

                                                                                                                                                                  Sandy bottom

                                                                                                                             Zostera marina







                                                                                                                             50cm

                                  Ecklonia stolonifera
                                                                                                  Ei@enija.';Z@
                                                                                                       C
                                                                                                    bicyc Ist
                                                                                                                                            120cm


                                                 A.Omorii
                                                                                                                              A.steueri

                                                        4%
                                              20                                                                Rock          0.0culat,
                                                                                                                                                      A.steueri
                                              cm                                                                                                       O.oculata


                                                 Gravel                              Rocky reef
                                                                                                                             Gravel                      Boulder-shingle
                                                                                                                                                                bottom



                                                                                                 Figure 2
                     Schematic illustrations of copepod swarming relative to bottom topography and materials in Shijiki Bay. a) Sandy bottom, b) Zostera matina bed,
                                                       c) shoal of small rocks with brown algae, d) shoal of large rocks with brown algae.




                     were made by SCUBA diving along a 50-m long graduated                                    A total of seven species of three genera were identified
                     nylon rope set on sandy bottom and eelgrass (Zostera niarina)                          from swarming copepod communities; three species of
                     bed, 4-12 in in depth (L stations, Fig. 1). Observations were                          Acartia, tw    /o of Oithona, and two of Tortanus (Table 1). A
                                                                                                                                                        ona      .1ala T-'
                                                                                                                                                                               Gill
                                                                                                                                                                vi
                                                                                                                                                         na  da a
                                                                                                                                                                                net























                                                 A


                                              2
                                                 0

















                     also made occasionally at gravelly and sandy bottom, 6-35                              swarm sometimes consisted of a single species or genus and
                     in in depth (S stations, Fig. 1). Swarming copepods were                               sometimes not. Species, stage, sex composition and shape
                     collected with a Van Dom water sampler (6 L) or plastic                                of swarm, and swarming location varied seasonally.
                     suction bottle (3 L) like a syringe, and a hand-operated
                     plankton net (50 jAm mesh opening).

                                                                                                     106









                    200-                                                                       400-
                          EM    Asteued CH-CVT                          a                                  Asteueri C11-CVr                         a
                    150         Aornorii CH-CV1                                                            Aomorfi CR-CVT
                                                                                               300-
                                Acortiospp. N-CI                                                           A cartia spp. N - CI
                22
                a   100-
                                                                                               200 -



                                    ..........                                                                                             R
                    50                                                                         100-


                    100                                                                        100
                    so-                                                                               Asteueri
                                                                                            Z:; 80-
                                                                                            >
                    60-                                                                        60-

                    40-                                                                        40-
                    20-                                                                     L) 20  -

                    100                                                                        100
                    80-                                                 C                      80 _    Asteuerl
                                                                                                                                                   C
                    Go-                                                                        60-

                E   40-                                                                        40-
                                A. steueri                                                  E
                LL
                    20-                                                                        20-
                       oi                                                                        0
                         12               1      11     21                                                          1       it      21       1      11
                                May            June                July                                   May             June                July


                                          Figure 3                                                                   Figure 4
            (a) Seasonal changes in number of Acarda steueyi and A. omorii, and         (a) Seasonal changes in number of Acarda steueri and A. omorV, and
            percentages of (b) adults and (c) females in each species of Acania         percentages of (b) adults and (c) females in A. steueri collected by
            collected by horizontal tow with plankton net at flat sandy bottom of       horizontal tow with plankton net at eelgrass (Zostera marina) bed of
                       inner part of SNiki Bay, 12 May-13 July 1984.                               inner part of Shijiki Bay, 12 May-13 July 1984.




                Acartia omorii and A. steueri formed continuous flat                        A. steueri and A. omorii in swarms on flat sandy bottom
            swarms usually 5-30 cm thick, just above the flat sandy                     were collected by horizontal tow of a plankton net. A number
            bottom in shallow waters 10-27 m depth (Stn. L-1, 2, S-1,                   of organisms, including all developmental stages of adults,
            3, 5, 7, 8; Fig. 2a) from spring to early summer. Thickness                 copepodites and nauplii, ranged from 8 to 190 per liter (Fig.
            and density of copepod swarms varied from place to place,                   3a). This value is much higher than that collected by an or-
            and may be affected by the configuration of sea bottom and                  dinary plankton-net vertical haul. The ratio of adults (CVI)
            current strength. In the Bay, copepods sometimes formed                     to copepodites (CH to CVI) for the above two species varied,
            a small ball or disk-shaped swarm. The sizes of swarms                      but the mean was about 60 percent (Fig. 3b). Females of
            ranged from 10 cm to a few meters in diameter, but bound-                   both species comprised about half of the adults (Fig. 3c).
            aries between swarm and background were not always clearly                      At eelgrass (Zostera marina) beds with a range of 2-7 m
            defined.                                                                    in depth (Sm. L-3, 4, 7, 9, 10, S- 1; Fig. 2b), dense swarms
                Copepod swarms were often observed in the lee of objects                of A. omorii and A. steueri were observed during the obser-
            on the bottom such as clumps of living or dead algae, rocks,                vational period from March to July. Copepods swarmed
            and trash. Swarm organisms usually held the same spatial                    within and near the eelgrass bed from the roots up to above
            position and swimming pattern against a moderate current.                   the grass blades. Density of organisms, consisting of adults,
            But when the current was stronger than about 5 cm/s,                        copepodites, and nauplii, collected by the horizontal net tow-
            copepods were carried away from their initial position by                   ing inside the swarm ranged between 14 and 342 per liter
            the current.                                                                (Fig. 4a). In Acartia swarms, adults were abuandant and
                Copepods swarm upward with a spiral movement and the                    females far outnumbered males, particularly in July (Fig.
            swarm dispersed throughout. the water column immediately                    4b, c). Acartia often swarmed in high densities along the
            after sunset. After sunrise the next morning, they swam                     edges of Zostera beds.
            downward and formed a swarm on the sea bottom again.



                                                                                   107







                   In the lee of rocks and brown algae, Ecklonia stolonifera,           are probably able to recognize other individuals by chemical
                 on a shoal (Stn. S-2, 4; Fig. 2c) 15-20 in deep in the central         (Katona 1973), optic, and physical stimuli and fulfill some
                 part of the Bay, A. omorii formed ball-shaped swarms with              organic functions.
                 a diameter of 10-30 cm. On the other hand, in shoals near                Adaptive functions of copepod swarms were suggested by
                 shore, 2-7 in deep in the inner part of the Bay, A. omorii             previous authors (Hamner and Carleton 1979, Omori and
                 and A. steueri formed large dense swarms in the lee of rocks           Hamner 1982, Ueda et al. 1983). Hamner and Carleton
                 and beds of brown algae (E. stolonifera, Eisenia bicyclis,             (1979) suggested four adaptive functions: Protection from
                 and Sargassum spp.) (Stn. S-6, L-5, 6; Fig. 2d). These                 predators, facilitating breeding, maintaining a favorable posi-
                 swarms were diverted right and left by waves. When dis-                tion. to feed on coral mucus, and restricting dispersion by
                 turbed by divers, they quickly resumed their initial position.         currents. They suggested that, although protection from
                   In summer, Oithona oculata formed swarms at a rocky                  predators was the most common and important adaptive ex.-
                 reef and a Zostera bed in the inner part of the Bay (Stn. S-6,         planation for copepod swarming, all these adaptive functions
                 L-4, 9, 10). The Oithona swarm was ball-shaped with a                  were responsible for denser populations on coral reefs.
                 diameter of 10 cm- I m. Density of the 0. oculata swarm                  The importance of these adaptive functions may vary
                 was higher than that of Acartia, ranging from 490 to 6490              among species. Reduction of dispersion by currents appears
                 individuals per liter. A small ball-shaped swarm, consisting           to be of major importance for the swarms in maintaining
                 of 0. oculata and Acartia sinjiensis, and large swarms, con-           populations of copepods. On the other hand, swarming prob-
                 sisting of Oithona davisae and A. steueri, were also formed            ably poses a contradiction: When swarming organisms are
                 at the edges of the Zostera bed.                                       distributed at the same space and time as demersal fishes,
                   A small cylindrical swarm of Tortanus longipes and T                 copepods tend to be eaten by fishes. Predation of A. steueli
                 rubidus was observed at the edge of the Zostera bed. In the            and A. omo?ii by demersal juveniles of red sea bream was
                 swarm, organisms moved in a swirl and maintained a cylin-              observed in the Bay (Tanaka 1985). This suggests that the
                 drical configuration.                                                  juveniles feed effectively on swarming Acartia, and, there-
                                                                                        fore, that copepod swarms are important in the feeding
                                                                                        strategy of some fishes during their early demersal life.
                 Swarming processes and functions                                       Copepod swarms could be induced by certain artificial struc-
                 of copepod swarms                                                      tures constructed on the sea bottom; thus it may be possible
                                                                                        to design a new nurseryground for juvenile fishes in the
                 In Shijiki Bay, swarms consisted of many copepodite stages,            future.
                 sometimes of a single species but also of a mixture of several
                 species. The density of a swarm was much higher than that
                 collected by ordinary vertical hauls of plankton net. Swarm-           Acknowledgments
                 ing during the day, copepodites of Acartia spp. and Oithona
                 spp. aggregated to a density several hundred times denser              The author is grateful to Dr. F. Koga and Dr. Y Morioka
                 than the mean density. However, the density changed both               of this Laboratory for encouragement and valuable sugges-
                 seasonally and daily, probably caused by seasonal popula-              tions in the above research and interpretation of results.
                 tion change and weather or tidal current conditions.                   Zooplankton sampling operations at sea were conducted with
                   Present results suggest that copepod swarming is closely             the assistance of J. Nakashima and crew members of the R/V
                 related to the microbottom topography and some materials               Youkou Maru of the Seikai Regional Fisheries Laboratory.
                 on the bottom. The author also observed a copepod swarm                Thanks are also due to the members of the Shijiki Fisheries
                 on artificial materials, e.g., a gill net for crab fishing set on      Cooperative Association, Hirado, for their interest and facil-
                 sandy bottom. Furthermore, the author could induce cope-               ities for field work.
                 pood swarms by field experiments with plastic boxes of                   This work was conducted under the research projects
                 different sizes (Kimoto unpubl.). Two processes of swarm-              "N/larine Ranching Program" (MRP 87-IV-2-1) and
                 ing by copepods were suggested: First is the increasing                "Coastal Fishing Ground Improvement and Development
                 copepod density near-bottom by day during their diurnal ver-           Program" supported by the Ministry of Agriculture, Forestry
                 tical migration; second is that copepods swimming near the             and Fisheries.
                 bottom are concentrated and form a much denser swarm in
                 the lee of materials such as clumps of living or dead algae,
                 rocks, and trash. The above copepods are probably carried
                 into the lee by moderate currents. The spatial position of a
                 copepod swarm is probably maintained by the wake formed
                 behind the materials on the bottom. This interpretation was
                 made by Kakimoto et al. (1983) who observed copepod (A.
                 clausi = A. omorii) and mysid (Proneomysisfasca) swarms
                 at natural and artificial reefs of the coastal area of Niigata
                 Prefecture, Japan Sea. Copepods gathered at a certain density

                                                                                   108







              Citations

              Byron, E.R., P.T. Wittman, and C.R. Goldman
                  1983 Observations of copepod swarms in Lake Tahoe. Limnol.
                     Oceanogr. 28:378-382.
              Emery, A.R.
                  1968 Preliminary observations on coral reef plankton. Limnol.
                     Oceanogr. 13:293-303.
              Hamner, W.M., and J.H. Carleton
                  1979 Copepod swarms: Attributes and role in coral reef ecosystems.
                     Limnol. Oceanogr. 24:1-14.
              Hebert, P.D.N., A.G. Good, and M.A. Mort
                  1980 Induced swarming in the predatory copepod Heterocope septen-
                     trionalis. Limnol. Oceanogr. 25:747-750.
              Kakimoto, H., H. Ookubo, H. Itano, and K. Arai
                  1983 Gyoshou ni okeru doubutsu purankuton no bunpu yousild ni tuite
                     (Distribution of zooplankton at artificial reefs). Fish. Eng. 19:21-28
                     [in Jpn.].
              Katons, S.K.
                  1973 Evidence for sex pheromones in planktonic copepods. Limnol.
                     Oceanogr. 18:574-583.
              Omori, M., and W.M. Hamer
                  1992 Patchy distribution of zooplanklon: Behavior, population assess-
                     ment and sampling problems. Mar. Biol. 72:193-200.
              Tanaka, M.
                  1985 Factors affecting the inshore migration of pelagic larval and
                     demersal juvenile red sea bream Pagrus nwjor to a nursery ground.
                     Trans. Am. Fish. Soc. 114:471-477.
              Ueda, H., A. Kuwahara, M. Tanaka, and M. Azeta
                  1983 Underwater observations on copepod swarms in temperate and
                     subtropical waters. Mar. Ecol. Prog. Ser. 11:165-171.











































                                                                                             109






           Feeding Ecology of                                                      Red sea bream Pagrus major is one of the most important
                                                                                   demersal fishes for coastal fisheries in Japan because of its
           Young Red Sea Bream                                                     high landings and high market price. Since the 200-mile
                         0                                                         fishing jurisdiction was established, exploitation of the ocean
           in S                     Bay                                            potential around Japan became more imperative to meet the
                                                                                   increasing demand for fish and shellfish of high quality.
                                                                                   Recently, projects of stock enhancement have been promoted
                                                                                   for the red sea bream through releasing operations, because
           HIROYUKISUDO'                                                           mass production of juveniles has been established for this
           Seikai National Fisheries Research Institute                            species in hatcheries. However, these releasing operations
           Fisheries Agency of Japan                                               do not appear to have always resulted in increases to red sea
           49 Kokubu-machi                                                         bream stocks. There are two main keys to success of these
           Nagasaki 850, Japan                                                     projects: One is the qualitative evaluation of artificially
                                                                                   propagated fish, and the other is accurate estimation of
                                                                                   carrying capacity. For the latter, it is most important to
                                                                                   understand fish biology and ecology.
           ABSTRACT                                                                  A series of investigations on the ecology of 0-age red sea
                                                                                   bream has been carried out since 1975 in Shijiki Bay to pro-
           Feeding ecology of red sea bream in ShUild Bay is explained             vide a biological basis for stock enhancement. The "Shijiki
           especially with (1) changes in diet with growth, (2) predator-          Project" deals with the early life history of red sea bream,
           prey interactions between young red sea bream and gammari-              fish communities, oceanographic conditions, primary and
           dean amphipods, and (3) feeding relationships between young             secondary production, experimental release of artificially
           red sea bream and other fish species. Juvenile and young red
           sea bream feed mainly on calanoid copepods and gammaridean              propagated young red sea bream, etc.
           amphipods, respectively, in the sandy bottom area of the inner            In the present paper I explain the living modes of red sea
           part of the bay. They feed on calanoids when the calanoid swarm         bream, especially feeding ecology of the young. I also
           is formed and on gammarids when the gammarid density is                 describe interspecific relationships between young red sea
           highest. Crimson sea brearn and stripedfin goatrish also change         bream and other fish species.
           their main food from calanoids to gammarids as they grow in
           the sandy bottom area of the inner part of the bay. However,
           the peak month of feeding on calanoids and gammarids by these           Living modes of red sea bream
           two fishes does not comcide with that of occurrence of each prey        in Sh@iki Bay
           item in the field. Furthermore, young red sea breant always feed
           mainly on gammarids, independent of coexistence with hairy-
           chin goby; hairychin goby shift their main food from gamma-             Environmental features
           rids to mysids in the presence of red sea bream. These facts            Shijiki Bay, about 10 km2 in area, is located at the southern
           demonstrate that young red sea bream have an advantage over             end of Hirado Island in Nagasaki Prefecture, northwestern
           other fish species in feeding relationships.                            Kyushu (Fig. 1). The bottom consists mostly of well-sorted
             Gammarids are the most important prey for young red sea
           bream; however, this fish cannot feed on all gammarid species           fine sand. Zostera marina grows in the inner part of the bay
           in the field. Young red sea bream can add gammarids to their            where the sandy bottom area is shallower than 7 in; Sar-
           diet when gammarids become epibenthic. This fact points out             gassum spp. grow in the reef area.
           the importance of discriminating the "true" prey species by               The flow pattern in Shijiki Bay indicates that the bay can
           species identification of prey organisms.                               be further subdivided. Two imaginary lines, one traced
                                                                                   between Megasaki and Nagatenohana and another between
                                                                                   Shiomibana and lidabana, divide the bay into three parts:
                                                                                   (1) the mouth is characterized by offshore waters; (2) the
                                                                                   interior is characterized by proper embayed waters; and (3)
                                                                                   the central area is characterized by a mixture of these two
                                                                                   water masses (Tamai 1980). These divisions are also sug-
                                                                                   gested by other environmental factors (Hamada 1980, Kiso
                                                                                   1980a, Sudo et al. 1983). Moreover, these divisions agree
                                                                                   with the distribution of zooplankton fauna (Ueda 1980),
                                                                                   macrobenthos fauna (Azuma and Jinno 1980) and fish fauna
                                                                                   (Nakabo 1980).

             'Current address until 9/90: School of Fisheries, WH-10, University of
           Washington, Seattle, WA 98195.












                                                                   13 E
                                                     Shijiki
                         50:
                                                      Ba
                                                                                                               WINrERING
                                                                USHU
                                                                                            MAR. MAY
                                                      Hirado'
                               30                       Is.
                                                       330N

                                             Megasaki

                                                                                                     PELAGIC LARVA
                                       20                                                            3--10WA (TL)
                                            .... ..   Shiomi-
                       Nagateno                       bana                                            APR. MAY
                       hana

                                                                                                                  WTNiiRING YOUNG

                                                                                                                      90 - 180MM (FL)
                                                                                                                          AUG.  MAIL
                          sandy bottom         'Id                                                           SM7LING JUVENILE
                                               ba                                                        I     10-20MR1 (FL)
                          eeigrass zone                                                                         MAY - JUNE       DEMERSAL JUVENILE
                      E
                          reef r boulder-       1km                                                                                 & YONUG
                        l shing(tl. zone                                                                                          25 - BOWA (FL)
                                                                                                                                   MAY - AUG
                                            Figure 1                                         ME* Immigration
                       Map of ShjUfld Bay, Japan (depth contours in meters).                 =>Emigration


                                                                                                                 Figure 2
                   Shijild Bay is essentially open because of the strong influ-        Growth and migration pattern of 0-age red sea bream in Shijfld Bay
                 ence of the Tsuchima Current and the absence of rivers flow-                              (Sudo and Azeta 1986).
                 ing into it. However, in the interior, detritus from seagrass
                 accumulates on the bottom and is decomposed by bacteria
                 under aerobic conditions (Sudo et al. 1983). The abundant             Feeding habits
                 detritus supports high productivity of benthic crustaceans,           ofyoung red sea bream
                 including gammaridean amphipods, and forms a healthy and
                 fertile nursery ground for fishes in the inner part of the bay.       Dietary changes with growth
                 Growth and migration                                                  0-age red sea bream in Shijiki Bay change their main food
                 The migration pattern of red sea bream in Shijild Bay is              with growth in the following order as shown in Figure 3 (Kiso
                 closely related to the environmental structure of the bay             1980b): calanoid copepods, gammaridgan amphipods, my-
                 (Fig. 2). Pelagic larvae hatch during March-May in offshore           sids. Dernersal juveniles occurring in the sandy bottom area
                 spawning grounds. They are transported by tidal currents              of the interior in late May feed mainly on calanoid copepods
                 and trapped by a circular current at the mouth of the bay.            swarming near the bottom (Tanaka 1985). From June through
                 When a little larger than 10 Imm in total length, larvae meta-        August, when juveniles and young are most dense there, they
                 morphose into pelagic juveniles. These juveniles begin to             feed heavily on gammaridean amphipods. These changes in
                 migrate into the bay beyond the boundary between the outer            diet appear to be related closely not only to prey size but
                 and inner water mass. After immigration into the bay,                 also to prey density. Red sea bream feed on calanoid cope-
                 juveniles become demersal at 12-15 mm total length in late            pods when the calanoid swarm is formed and on gammari-
                 May (Tanaka 1980, 1985).                                              dean amphipods when the gammarid density is highest (Fig.
                   Demersal juveniles feed on calanoid copepods swarming               4). Furthermore, young red sea bream are densely distributed
                 near the bottom, and gradually concentrate in the sandy bot-          at sites where gammarideart amplupods are abundant (Azeta
                 tom area of the interior. There, they feed heavily on gam-            et al. 1980, Sudo et al. 1983). These facts emphasize that
                 maridean amphipods and grow at the rate of 0.7 mm per day.            gammAridean amphipods are the most important prey for
                 In June they reach the young stage, and in August they grow           young red sea bream.
                 to 70-90 mm fork length and begin to extend their habitat             Predator-prey relationships
                 toward the central area. While extending their habitat, mysids
                 and other food items are added to their diet. The majority            Sudo et al. (1987) explained diel changes in predator-prey
                 emigrate outside of the bay for wintering in September,               relationships between red sea brearn and gammaridean am-
                 although some remain in the bay until the next August (Azeta          phipods. In Shijild Bay, over 100 species of gammarids have
                 et al. 1980, Sudo et al. 1983).                                       been collected, and about 60 species of these occurred in the

                                                                                 112










                100
                                                 Copepoda


                                      %          G a m m a r i d e a                  10
                8
                  0                                                                 E

                                                  Mysidacea


                                                                                    W
                60
             LU
             U
             Z
                                                                                       5
             W                                                                      2
             cr_
                40                                                                  U_
                                                                                    0

             0
                                                                                    Z

                20
                                                                                       0
                                                                                           M A M J J A S 0 N D J F
                                                                                                               MONTH
                  0
                   0     2    4     6     8    10 12 14 16                                                Figure 4
                                FOLK LENGTH (cm                                 Monthly changes in density of gammarldean amphipods (mean ï¿½ I SID)
                                                                                in the sandy bottom area of the interior of Shijiki Bay April 1983-
                                     Figure 3                                    February 1984. Shaded zone indicates observed copepod swarm.
           Changes in diet of 0-age red sea bream with growth (Kiso 1980b).


                                                                                types. Infaunal tube-dwelling types (e.g., Bybfisjaponicus)
           sandy bottom area of the interior. However, about 50% of             were positively or negatively selected with diel time. Deep
           gammarid species in this area occurred in stomachs of young          burrowing types (e.g., Harpiniopsis vadiculus, Urothoe sp.
           red sea bream. Moreover, seven species each surpassed 10%            B, and Urothoe sp. C) were negatively selected or hardly
           of the gammarids consumed: Bybfisjaponicus, Synchelidium             consumed (Fig. 5). These results indicate that the availability
           miraculum lenorostralum, Paradexamine ntarlie, Aoroides              of gammarid species increases with the decrease of gammarid
           columbiae, Melita denticulata, Gitanopsis longus, and Tiron          living-depth in the sediment. This finding is consistent with
           sp. The proportion of the sum of these seven species to total        my underwater observations that young red sea bream, a
           gammarids in the stomachs ranged from 61.8% to 94.7%                 visual feeder, normally swim off the bottom and peck at prey
           with diel time. Of these seven, Byblisjaponicus was the most         organisms only when recognizing 'them.
           important prey species, because it was the most frequently             However, there were diel changes in the pattern of pre-
           consumed and largest in body length. Synchelidium mira-              dation on gammarid species by young red sea bream. The
           culum lenorostralum, Parad@ximine marlie, and Melita den-            intensity of predation on Bybfisjaponicus was low about noon
           ficulata were also important prey species, because of their          but increased remarkably at dusk and dawn, whereas that
           high frequency of occurrence and their large body size.              on Synchel0um nuraculwn lenorostralum and Paradexarmne
             Comparing relative abundance of gammarid species in the            ntarlie increased about noon. This diel dietary shift is caused
           stomachs with that in the field, individual gammarid species         by diel vertical movements of gammarids, because vertical
           were not consumed relative to their abundances in the field.         movements change their microhabitat and consequently in-
           This difference between gammarid composition in the                  fluence their availability. Byblis japonicus, the most domi-
           stomachs and in the field is believed to be due to the differ-       nant species of gammarids in the field, lives in the tube in
           ence in availability of gammarid species. Stoner (1979)              daytime; however, this species comes to the bottom surface
           pointed out that amphipod selection by the pinfish Lagodon           in large numbers from dusk to dawn. On the other hand, Syn-
           rhomboides was related most closely to the microhabitat of           chelidium miraculum lenorostralum digs in the superficial
           amphipod species, and important prey species were all                bottom sand exposing its dorsal part in the daytime, but
           epifaunal types. In Shijiki Bay, the patterns of gammarid            swims up to the water column near the bottom in large
           selection by young red sea brearn also correlated with the           numbers at night; Paradeximine marlie lives on the bottom
           microhabitat of gammarid species. Epifaunal (e.g., Paradeex-         surface in the daytime but swims up the water column to near
           amine marlie) and shallow burrowing types (e.g., Syn-                surface in large numbers at night. Young red sea bream can-
           chelidium miraculum lenorostralum) both were positively              not feed fully on Byblisjaponicus in the daytime, when this
           selected as prey, although the degree of selectivity for epi-        gammarid is in the tube; however, they can feed heavily on
           faunal types was higher than that for shallow burrowing              Bybfisjaponicus at dusk and dawn when it is on the bottom

                                                                           113





Figure 5

Diel charges in microhabitat composition of gammarids in stomacks
of young red sea bream (left) and in the field (right): EF, epifauna;
SB, shallow burrower; DB, deep burrower; IT, infaunal tube dweller
		(Sudo et al. 1987).


surface or in the water column near bottom in large numbers
(young red sea bream cease to feed after dark). On the other
hand, they can feed on Synchelidium miraculum lenorostra-
lum and Paradexamine marlie in the daytime, when both
gammarids live on the bottom surface (Fig.6). Thus, the 
diel dietary shift of young red sea bream does not contradict
the thesis that epibenthic gammarids are most available.
However, once gammarids come to the bottom surface, their
abundance, body size, and moving speed (swimming or
crawling) appear to become major factors influencing prey
selectivity. In fact, Byblis japonicus, which was more abun-
dant, larger in body length, and slower in movement (judg-
ing from its body shape and type of appendages)(Bousfield
1973), was subjected to heaview predation by young red sea
bream than the other two gammarid species when it came 
to the bottom surface.

												Figure 6
Interspecific relationships							Diel predation patterns on three gammarid species heavily consumed
											by young red sea bream (upper), and diel vertical movement patterns
Sudo and Azeta (1986) described the interspecific relation-		of each gammarid species (lower). Black bars represent hours of
ships of young red sea bream to other fish species by			darkness. numerals indicate number of each gammarid species collected
comparing their niches. Here, in particular, I examine the 		by on horizontal tow of larval net in water column (Sudo et al. 1987).
feeding relationships among fishes. The niche has three main
demensions: time, habitat, and food (e.g., Pianka 1974,
Christiansen and Fenchel 1977). Thus, the minor habitat 		sandy bottom; (2) rocky bottom; and (3) eelgrass zone. Crim-
among fishes is compared first and the fish species coexis-		son sea bream (Evynnis japonica), stripedfin goatfish (upe-
tent with red sea bream are picked out. Then their seasonal		Neus bensasi), and hairchin goby (Sagamia geneionema) as
occurrence patterns and food habits are compared			will as red sea bream belong to the sandy bottom group.
	According to habitat analysis og demersal fishes with the 	Thus, seasonal occurrence patterns of these three species in
index of interspecific overlapping (Cd) of Morisita (1959),		the sandy bottoms area of the interior are compared with that
fishes in the interior were divided into three groups: (1)		of red sea bream. Crimson sea bream and stripedfin goatfish

114








                                                                                                                          Coexist                     Separate
                                                                                                                                   Gammaridea
                                                                                                         +1                                                          0
                 X


                 Z
                 a- 0.5                                                                                   0
                                                                                                                         51              50          5      50      500
                                                                                                     X
                 LU                                                                                  L1J
                 >.                                                                                  0
                 0


                                                                                                                       0                                              0
                       0
                                 May                 June                July                                                        Mysidacea
                                                     MONTH

                                                                                                     LJJ
                                                                                                     _J
                                              Figure 7                                               Ld
               Changes in diet overlap index between red sea bream and hairychin                          0
               goby in the sandy bottom area of the interior of Shijiki Bay (Sudo and                                      10            100            100       1000
                                             Azeta 1986).



                                                                                                                                                            0        0
               differ from red sea bream in the peak month of occurrence                                                     PREY SUPPLY INDEX
               (crimson sea bream, mid-May; red sea bream, mid-June to
               mid-July; stripedfin goatfish, mid-August). On the other                                                           Figure 8
               hand, hairychin goby overlap with red sea bream in both                            IvIev's electivity indices of gammarids (top) and mysids (bottom)
               minor habitat and seasonal occurrence pattern. Moreover,                           consumed by red sea bream (closed circle) and hairychin goby (open
               these two species rank high in number among dernersal fishes                       circle) plotted agamst prey supply indices. Prey supply index = Biomass
               every year. Thus, the food habits of hairychin goby are com-                       of each two prey/total number of two fish species. On the left: electiv-
                                                                                                  Ity indices at sites where the two fish species coexist; on the right- elec-
               pared with those of red sea bream.                                                 tivity indices at sites where the two fish species do not coexist (Sudo
                 Hairychin goby occurring in the sandy bottom area of the                                  and Azeta 1986, modified from Azuma et al. 1993).
               interior in late May feed mainly on calanoid copepods swarm-
               ing near bottom. They then feed mainly on mysids from June
               through July; in August the majority migrate to the eelgrass
               zone in the interior (Matsumiya et al. 1980). The diet over-                       in gammarid supply, independent of the coexistence with red
               lap index (a) of Schoener (1970) between red sea bream and                         sea bream.
               hairychin goby is highest in late May when both are few in                            These results suggest that young red sea bream always feed
               number, because both species feed on the same calanoid                             mainly on gammarids, independent of the coexistence with
               copepods. In June, when both increase in number, however,                          hairychin goby; hairychin goby shift their main food from
               diet overlapping becomes insignificant, and the diet overlap                       garnmarids to mysids in the presence of red sea bream. How-
               index is lowest at their peaks of abundance in mid-June (Fig.                      ever, the degree of this food segregation varies with gam-
               7). This is because red sea bream feed mainly on gammarids                         marid supply: more pronounced when gammarid supply is
               whereas hairychin goby feed mainly on mysids.                                      limited, but less pronounced or nonexistent when gammarid
                 Figure 8 shows electivity indices (Ivlev 1961) of gamma-                         supply is abundant. The term "interactive segregation" was
               rids and mysids consumed by red sea bream and hairychin                            defined by Brian (1956) to mean that ecological differences
               goby plotted against prey supply indices (prey supply index                        between species are magnified by interaction. In practice,
               = biomass of each prey/total number of two fish species).                          however, it is often difficult to prove that segregation is a
               As is evident from Figure 8, red sea bream prefer gamma-                           direct result of interaction or ecological divergence, as stated
               rids whereas hairychin goby prefer mysids, at sites where                          by Nilsson (1967). However, the process of food segrega-
               the two fish species coexist. On the other hand, at sites where                    tion between young red sea bream and hairychin goby in
               the two fish species do not coexist, hairychin goby also prefer                    Shijiki Bay shows that interactive segregation occurs between
               to feed on gammarids.                                                              the two species as a result of the dietary shift only by
                 The relation between the electivity index and the prey                           hairychin goby.
               supply index in Figure 8 demonstrates that red sea bream
               select gammarids more strongly with the increase of gamma-
               rid supply; however, there is no correlation between mysid
               selection by hairychin goby and mysid supply although
               mysids are the main food for hairychin goby. Moreover,
               hairychin goby begin to select garnmarids with the increase

                                                                                            115







                   Citations                                                                            Sudo, H., R. Ikernoto, and M. Azeta
                                                                                                             1983 Studies on habitat quality evaluation of red sea brearn youngs
                   Azeta, M., R. Ikemoto, and M. Azama                                                         in Shijild Bay. Bull. Seikai Reg. Fish. Res. Lab. 59:71-84 [in Jpn.,
                       1980 Distribution and growth of demersal 0-age red sea brearn, Pagna                    Engl. abstr.].
                          major, in Shijild Bay. Bull. Se" Reg. Fish. Res. Lab. 54:259-278              Sudo, H., M. Azmna, and M. Azeta
                          [in Jpn., Engl. abstr.].                                                           1987 Diel changes in predator-prey relationships between red sea
                   Azuma, M., and S. Jinno                                                                     brearn and gammaridean amphipods in ShijibBay. Nippon Suisan
                       1980 The bottom fauna communities in Shijild Bay, Hirado Island-1.                      Gakkaishi 53:1567-1575.
                          An attempt at analysing habitat based on animal-sediment relations.           Tamai, K.
                          Bull. Seikai Reg. Fish. Res. Lab. 54:195-208 [in Jpn., Engl. abstr.].              1980 The flow pattern in Shijild Bay-I. A pattern obtained in winter,
                   Azmna, M., M. Azeta, and K. Mitsumaru                                                       1975. Bull. Seikai Reg. Fish. Res. Lab. 54:157-169 [in Jpn., Engl.
                       1983 Feeding interrelationships between young red sea brearn and                        abstr.].
                          cohabiting fishes in Shijild Bay. Bull. Seikai Reg. Fish. Res. Lab.           TanWia, M.
                          59:101-118 [in Jpn., Engl. abstr.].                                                1'980 The ecological studies on the larvae and juveniles of red sea
                   Bousfleld, E.L.                                                                             brearn in Shijild Bay-I. The horizontal distribution of the pelagic
                       1973 Shallow-water gammaridean Amphipoda of New England.                                larvae and juveniles in and outside the bay. Bull. Seikai Reg. Fish.
                          Cornell Univ. Press, Ithaca and London, 312 p.                                       Res. Lab. 54:231-258 [in Jpn., Engl. abstr].
                   Brian, M.V.                                                                               11"5 Factors affecting the inshore migration of pelagic larvae and
                       1956 Segregation of species of the ant genus Atm7dba. J. Anim. Ecol.                    demersal juvenile red sea brearn Pagrus nwjor to a nursery ground.
                          25:319-337.                                                                          Trans. Am. Fish. Soc. 114:471-477.
                   Christiansen, F.B., and T.M. Fenchel                                                 Ueda, T.
                       1977 Theories of populations in biological communities. Springer-                     1980 Zooplankton investigations in Shijild Bay-L Compositions of
                          Verlag, NY, 144 p.                                                                   zooplankton and distributions of copepods from April to August, 1975.
                   Hamads, S.                                                                                  Bull. Seikai Reg. Fish. Res. Lab. 54:171-194 [in Jpn., Engl. abstr.].
                       1980 Hydrographic characteristics of Shijiki Bay. Bull. Seikai Reg.
                          Fish. Res. Lab. 54:141-155 [in Jpn., Engl. abstr].
                   IvIev, V.S.
                       1%1 Experimental ecology of the feeding of fishes. Yale Univ.
                          Press, New Haven, 302 p.
                   Kiso, K.
                       1980a The bottom topography and grain size distribution of bottom
                          sediment in Shijild Bay, Hirado Island. Bull. Seikai Reg. Fish. Res.
                          Lab. 54:135-140 [in Jpn., Engl. abstr.].
                       1980b On the feeding habit of 0-group red sea brearn (Pagrus major)
                          in Shijiki Bay, Hirado Island-1. Sequential changes of diet with
                          growth and its annual variation. Bull. Seikai Reg. Fish. Res. Lab.
                          54:291-306 [in Jpn., Engl. abstr.].
                   Matsumiya, Y., T. Murakami, T. Suzuki, and M. Oka
                       1980 Some ecological observation on gobies, Sagamia geneionema
                          and Rhingobiuspftaumi, in ShiJild Bay. Bull. Seikai Reg. Fish. Res.
                          Lab. 54:321-332 [in Jpn., Engl. abstr.].
                   Morlsita, M.
                       1959 Measuring of interspecific association and similarity between
                          communities. Mem. Fac. Sci. Kyushu Univ., Ser. E. (Biol.)
                          3:65-80.
                   Nakabo, T.
                       1980 Demersal fish community in Shijild Bay-I. Distribution of some
                          species and division of the community. Bull. Seikai Reg. Fish. Res.
                          Lab. 54:209-229 [in Jpn., Engl. abstr.].
                   Nilsson, N-A.
                       1%7 Interactive segregation between fish species. InGerking,S.D.
                          (ed.), The biological basis of freshwater fish production, p. 295-313.
                          Blackwell Sci. Publ., Oxford and Edinburg.
                   Pianka, E.R.
                       1974 Niche overlap and diffuse competition. Proc. Nail. Acad. Sci.
                          USA 71:2142-2145.
                   Schoener, T.W.
                       1970 Nonsynchronous spacial overlap of lizards in patchy habitats.
                          Ecology 51:408-418.
                   Stoner, A.W.
                       1979 Species-specific predation on amphipod Crustacea by the pin-
                          fish Lagodon rhomboides: Mediation by macrophyte standing crop.
                          Mar. Biol. 55:201-207.
                   Sudo, H., and M. Azeta
                       1986 Species inteffelationships on food and habitat utilization in fishes
                          of Shijiki Bay. Int. North Pac. Fish. Comm. Bull. 47:129-141.



                                                                                                 116






            hnportance of                                                            In the last decade, artificial propagation of marine animals
            Q           0                                                            has been vigorously pursued with a tremendous increase in
                uaRtative Evaluation                                                 total production and number of species raised in the hatchery
                                                                                     (Fukuhara 1983, Kuronuma and Fukusho 1984, Nose 1985).
            of Hatchery-bred Fish                                                    This phenomena resulted from the diversity of consumer
                                                                                     demand which promoted the releasing program to enhance
            for Aquaculture                                                          coastal fishery and aquaculture activity.
                                                                                       In Japan, fishermen raised fry from the egg stage for their
                                                                                     cage cultures, whereas fish seeds for restocking are produced
                                                                                     by the national and prefectural governments. The produc-
            OSAMU FUKUHARA                                                           tion of fish for releasing now totals 50 million per year. The
            Nansei Regional Fisheries Research Laboratory                            major species for planting are red sea bream Pagrus major,
            Ohno, Saeki-gun,                                                         Japanese flounder Paralichthys olivaceus, and porgy Acan-
            Hiroshima 739-04, Japan                                                  thopagrus schlegeli (Fig. 1). Despite the great effort in
                                                                                     planting artificially reared animals, little information exists
                                                                                     on its effectiveness in fisheries after release into the sea. The
                                                                                     need for fundamental knowledge of quantity, size, and quality
            ABSTRACT                                                                 is a major obstacle in considering the effect of releasing
                                                                                     activities. More studies on quality evaluation and releasing
            Mass production techniques for commercially important species            techniques are urgently needed. The purpose of this paper
            have advanced for a decade in Japan. Numerous hatchery-                  is to review the qualitative differences between wild and
            reared fish are used for not only cage culture but also for              hatchery-reared fish and to emphasize the necessity of quali-
            releasing programs. However, little information exists on deter-         tative evaluation of hatchery-bred fish in aquaculture.
            mining the quality and survival potential of hatchery-reared fish.
            A comparison between reared and wild fish is a prerequisite
            for the effective use of farmed fingerlings in aquaculture ac-           Differences between wild
            tivities. This paper attempts to review, understand, and con-
            trast the biological features of hatchery-reared fish with those         and reared rish
            of wild fish and to search for the causes of those differences.
            Various steps in evaluating the quality of reared fish in the            Numerous studies on differences in quality between wild and
            hatchery are discussed from a practical viewpoint.                       reared fish have appeared for salmon and trout (e.g., Phillips
                                                                                     et al. 1957, Vincent 1960, Wood et al. 1960, Green 1964,
                                                                                     Bams 1967, Kobayashi and Ohkuma 1983). Special atten-
                                                                                     tion was given to determining measures of quality and to
                                                                                     exercising the fry to improve their survival potential in the
                                                                                     case of anadromous fish. Concerning marine fish, in spite
                                                                                     of their great economic importance, few basic data on bio-
                                                                                     logical characteristics of hatchery-raised fish are available.
                                                                                     Table 1 shows the differences in biochemical and morpho-
                                                                                     logical aspects of sparid fish. Artificially reared fish have
                                                                                     been shown in most cases to display a pronounced inferior-
                                                                                     ity to wild fish both in behavior and survival potential. High
                                                                                     lipid content is a biochemical feature of reared fish in general,
                                                                                     as well as red sea bream. It is uncertain whether the inferior-
                                                                                     ity of reared fish has any effect on survival potential follow-
                                                                                     ing transfer to the sea.
                                                                                       The general explanation for the poor quality of reared fish
                                                                                     is that environmental conditions of reared fish differ largely
                                                                                     from those in the wild. In the hatchery, a high percentage
                                                                                     of fish can survive due to lack of predation, starvation, and
                                                                                     lethal environmental changes, in other words, "selection
                                                                                     pressure" (Blaxter 1975). Newly hatched larvae which
                                                                                     would die in the wild are capable of feeding on prey and
                                                                                     surviving under enhanced rearing conditions. The variation
                                                                                     in size can be observed even at the egg stage and also in newly
                                                                                     hatched larvae in any species. Morphological differences,

                                                                                117










                                                                   for Releasing


                                                                  Others                                                                 pagrus
                                                                     11%                                                Others               major
                                                                                                                        25%                    45%
                                                        Crustacea
                                                            21%             70..         -is 'e@
                                                                        species           45%             parplichthys           million
                                                                                                                 ofivaceus
                                                                  Mollusca                                              17%
                                                                      23%                                                        13%                                                           01



                                                                                                                            Acanthopagrus
                                                                 for Cage culture                                                  schlegeli

                                             Crustacea
                                                   3%              Others
                                                                       10%



                                                                             29                 S
                                                          Mollusca       species
                                                             41%






                                                                                              Fkwe I
                                        Species composition of artificial propagation for releasing and cage culture, and total number of fry pro-
                                        duced in releasing program. (Source: Annual report of artificial releasing of reared marine seeds, Fishery
                                                                                 agency, Jpn. Farm Fish. Assoc.)




                                                                                              Table 1
                                                               Biological differences between wild and reared fry in sparid rish

                     Species                          Items*                                  Wild                      Reared                   Source

                     Pagrus major                     Water                                   78-79%                    82-72%                   Anraku and Azeta (1973)
                                                      Lipid                                   2-10 mg                   3-400 mg
                                                      Carbon                                  35-43%                    42-49%
                                                      Hydrogen                                5.2-6.2%                  5.9-6.7%
                                                      Nitrogen                                10.0-12.1%                9.5-11.6%
                                                      CIN                                     3.4-3.8                   3.7-5.0
                                                      Response to threat                      Sensitive                 Weak                     Tateishi (1974)
                                                      Abdominal fat content                                             Higher
                                                      Size of fish with complete              11.5 nun SL               9.0 mm SL                Fukuhara and Kuniyuki (1978)
                                                         stripes
                                                      Total lipids                            1.00- 1.05                1.95-2.04                0hshima et al. (1983)
                                                      Body height, eye diameter,                                        Smaller                  Matsumiya et al. (1984)
                                                        upper jaw length
                                                                                                               (lich    ys
                                                                                                                        c-us
                                                                                                                 01i    th!7%
                                                                                                                     va

                                                                                                                        I


























































                                                      Muscle freshness                                                  Decreased more           Iwamoto and Yamanaka (1986)
                                                                                                                        rapidly
                     Oplegnathus fasciatus            Malformation of stripes                 19.8%                     23.2-81.3%               Fukusho (1979)

                     *Percent wet weight for water content; percent dry weight for others.


                                                                                                 118







            particularly size at early life stage, lead to size hierarchy and
            differences in fish activities (Yamagishi 1964).                              100-                                   PNR
              Morphological changes in eggs and larvae depend largely
            on the nutritional conditions of spawning fish of red sea
            bream. (Watanabe et al. 1984). To observe the survival curve,
            Keitoku et al. (1985) conducted a starvation experiment of                     80-
            larval red sea brearn maintained simultaneously in a large-
                                                                                                                                             . ........
            scale tank used for artificial propagation. The starvation ex-
            periment indicated the existence of poor-quality larvae which               >  60-
            died prior to the point of no return (PNR) (Fig. 2), and a                  >
            close relationship was found between survival in the starva-
            tion test and percent survival of fish at harvest in the hatchery
                                                                                        r- 40-
            production unit. These findings suggested the source of dif-
            ference in fish quality is related to the health of broodstock
            or developmental stages of newly hatched larvae. In addi-                   a.
            tion, larvae are free from starvation and predation pressure                   20-
            in the rearing tank, which allows non-exercised fish to avoid
            various lethal conditions and experience a high survival rate.
            Biological characteristics of non-exercised fish become fixed                   0        1                     . . . . . . . . . . . . . .. . . . . .
            as the rearing period lengthens, leading to a loss of wildness                      1   2     3    4     5    6     7    8     9   10
            and to an inability of the hatchery-reared fish to adjust to                                 Days after hatching
            new surroundings after transfer (Azuma 1974, Blaxter 1975).
                                                                                                               Figure 2
                                                                                       Survival curves for larval red sea brearn in unfed condition.
            Determining fish quality                                                PNR = point of no return. Redrawn from Keitoku et al. 1985 and
                                                                                                            Fukuhara 1974.)
            Stamina tunnels or swimming performance have been used
            to evaluate the quality of planted salmon and trout (e.g.,
            Vincent 1960, Green 1964, Barns 1967). As for marine fish,
            various examinations have been used to determine fish                   Conclusions
            quality: rheotaxis, resistance to exposure, starvation, low
            oxygen concentrations, and narcotization (Kitajima et al.               It can be reasoned that qualitative differences exist between
            1980, Ohgarni and Suzuki 1983, Keitoku et al. 1985,                     reared and wild fish if biotic and abiotic conditions are com-
            Maruyama 1985). An exposure test was employed to com-                   pared. The causes of differences in both aninials are mainly
            pare the activity of reared juveniles in a nutritional experi-          attributable to differences in feeding and habitat situations.
            ment. Mortality and recovery time of examined juveniles                 Hatchery-reared fish are immediately subjected to reduced
            usually correlate with nutritional conditions (Kitajima et al.          food levels and the threat of predation following transplan-
            1978, 1980). Maruyama (1985) compared mortality and                     tation. To alleviate various stresses to newly introduced fish,
            recovery time, following a 2-minute exposure, between con-              some manipulation (such as exposure to moving water,
            ventionally reared fish and semi-wild fish reared in an earthen         predators, and starvation) is required during the course of
            pond. One minute after exposure, 80% of the semi-wild fish              rearing or before planting. Fish exposed to predators were
            recovered with no mortality. On the other hand, less than               less vulnerable to predation, resulting in decreased fry mor-
            25 % of the hatchery-reared fish recovered after I minute with          tality (Ginetz and Larkin 1976). Henderson (1980) empha-
            50 % mortality. These observations suggest that an exposure             sized the necessity of certain durations for transplanted fish:
            test is available which may predict the activity of reared fish         periods of recovery of normal movement, familiarization
            under different conditions, and that the differences are caused         with the new habitat, and adjustment of feeding habit. As
            by different habitat and/or food items previously ingested.             already mentioned for Ayu fish, exercise in a water current
              In Ayu fish Plecoglossus altivelis, a freshwater species,             is a profitable strategy prior to planting. Swimming exer-
            swimming performance is usually employed to assess the                  cise increased endurance in trained coho salmon compared
            migrant behavior of hatchery-reared fish (Fig. 3). Fish raised          with control groups, and the effect of exercise was main-
            under lotic conditions showed a higher percentage of migrant            tained for 2 months (Besner and Smith 1983).
            behavior than those under lentic conditions. Adjustment to                These studies indicate that some manipulations are effec-
            water current of 30-60 cm/sec prior to planting is effective            tive in exercising and ajusting reared fry prior to release in
            for this species in increasing upstream movement (Hiroshima             a new habitat. As for marine fish production, to improve
            Prefect. Freshwater Fish Cent. 1983).                                   the quality of reared fish and to increase the survival poten-
                                                                                    tial after planting, the inferiority of laboratory-reared fish
                                                                                    must be prevented during rearing (Fig. 4). The concept of

                                                                               119
























                                                                                         Figure 3
                                                           Diagram of apparatus to determine mignint behavior in Ayu fish.




                                                                              Overcoming of inferl6qi14


                                                                                                                       Quality
                                                                                                  Exercise             evaluation


                                             F
                                        Parent         99       Newly hatched           Rearing                 Intermediate              Releasing]
                                            A                   larva                                           breeding

                                                                               Starvation


                                                                               Elimination           LCI r@i _ty_@@@@


                                                                                         Figure 4
                                        Concept for evaluating and improving Mh quality in artificud propagation and releasing procedures.



                 exercise and adjustment is not currently employed in rear-                       Citations
                 ing procedures from egg stage to young. Starvation tests of                      Anraku, M., and M. Azeta
                 newly hatched larvae before reaching PNR indicate the pos-                            :1973 Difference of body components between artificially reared and
                 sibility of selecting viable larvae for production purposes                             natural sea brearn: larva and young. Bull. Seikai Reg. Fish. Res.
                 (Fukuhara 1974, Keitoku et al. 1985). Experimentally, hatch-                            Lab. 43:117-131.
                 ery fish reared in a water current are usually resistant to                      Azuma, M.
                 handling procedures during transfer.                                                  t974 Planting experiments of hatchery and wild Ayu-fish into streams
                    In Japan, intermediate rearing of marine fish is generally                           and some biological problems of the farming fishery. Jpn. J.
                                                                                                         Michurin Biol. 10: 116-122.
                 conducted in net cages before their release. This intermediate                   Barns, R.A.
                 rearing is aimed in most cases at improving the effectiveness                         1%7 Differences in performance of naturally and artificially propa-
                 of the rearing facility and increasing fish length prior to re-                         gated sockeye salmon migrant fry, as measured with swimming and
                 lease. Exercise and exposure to starvation and predation are                            predation tests. J. Fish. Res. Board Can. 24:1117-1153.
                 needed to improve fish quality in the intermediate rearing                       Besner, M., and L.S. Smith
                                                                                                       1983 Modification of swimming mode and stamina in two stocks of
                 strategy. Quality determinations of reared fish become more                             coho salmon (Oncorhynchus kisutch) by differing levels of long-term
                 important to the evaluation of artificial recruitment effects                           continuous exercise. Can. J. Fish. Aquat. Sci. 40:933-939.
                 as releasing activities are carried out vigorously for various                   Blaxter, J.H.S.
                 marine fishes in the future. In turn, releasing techniques must                       1975 Reared and wild fish-how do they compare? In Euro. Symp.
                 be established to produce planting seeds which meed the                                 Mar. Biol., 10th Ostend, Belgium, ed. G. Persone and E. Jaspers.
                                                                                                         Vol. 1, Mariculture, p. 11-26. Inst. Mar. Sci. Res., Bredene,
                 biological characteristics needed for aquaculture ventures.                             Belgium.

                                                                                             120








               Fukuhara, 0.                                                                           Nose, T.
                    1974 The influence of initial delay of feeding on survival, growth and                 1985 Recent advances in aquaculture in Japan. Geojournal 10:
                      development of the red sea brearn larvae, Chrysophrys major Tem-                       261-276.
                      minck et Shlegel. Bull. Nansei Reg. Fish. Res. Lab. 7:19-29.                    Ohgami, H., and T. Suzuki
                    1983 Recent trends in mariculture and seed production of fish in                       1983 Examination of activity determination for larval red sea
                      southern Japan. In Sindermann, C.J. (ed.), Reproduction, matura-                       brearn. Tech. Rep. Shizuoka Prefect. Farm. Fish. Cent. Fiscal Year
                      tion, and seed production of cultured species; Proceedings, Twelfth                    57:50-56. Ogawa, Shiori 3690, Yaizu, 425 Shizuoka [in Jpn.].
                      U.S. -Japan Meeting on Aquaculture, Baton Rouge, Louisiana, Octo-               Ohshirna, T., S. Wada, and C. Koizumi
                      ber 25-29, 1983, p. 1-2. NOAA Tech, Rep. NMFS 47, Natl.                              1983 Comparison of lipids between cultured and wild sea bream.
                      Oceanic Atmos. Admin., Natl. Mar. Fish. Serv., Seattle, WA                             Bull. Jpn. Soc. Sci. Fish. 49:1405-1410.
                      98115-W70.                                                                      Phillips, A.M. Jr., D.R. Brockway, F.E. Lovelace, and H.A. Podoliak
               FtAuhara, 0., and K. Kuniyuki                                                               1957 A chemical composition of hatchery and wild brook trout.
                    1978 Morphological development in the wild larvae of Madai, Chry-                        Prog. Fish-Cult. 19:19-25.
                      sophrys major, as compared to that in the laboratory-reared larvae.             Tateishi, M.
                      Bull. Nansei Reg. Fish. Res. Lab. 11:19-25.                                          1974 On the ecology and results of tagging experiments of red sea
               Fukusho, K.                                                                                   brearn in the waters along western Kyushu. Jim J. Michurin Biol.
                    1979 Studies on fry production of Japanese striped knifeJaw Opleg-                       10:129-139.
                      nathusfasciatus, with special reference to feeding ecology and mass             Vincent, R.E.
                      culture of food organism. Spec. Rep. Nagasaki Prefect. Inst. Fish.                   1960 Some influence of domestication upon three stocks of brook trout
                      6; 173 p.                                                                              (Salvelinusfontinalis Mitchill). Trans. Am. Fish. Soc. 89:35-52.
               Ginetz, R.M., and P.A. Larkin                                                          Watanabe, T., T. Arakawa, C. KitaJima, and S. Fujita
                    1976 Factors affecting rainbow trout (Salmo gairdnen) predation on                     1984 Effect of nutritional quality of broodstock diets on reproduc-
                      migrant fry of Sockeye salmon (Oncorhynchus nerka). J. Fish. Res.                      tion of red sea bream. Bull. Jpn. Soc. Sci. Fish. 50:495-501.
                      Board Can. 33:19-24.                                                            Wood, E.M., W.T. Yasutake, J.E. Halver, and S.N. Woodall
               Green, D.M.                                                                                 1960 Chemical and histological studies of wild and hatchery salmon
                    1964 A comparison of stamina of brook trout from wild and domestic                       in fresh water. Trans. Am. Fish. Soc. 89:301-307.
                      parents. Trans. Am. Fish. Soc. 93:96-100.                                       Yamagishi, H.
               Henderson, H.F.                                                                             1964 Growth variations of fish. Biol. Sci. 16:98-104 [in Jpn.].
                    1980 Behavioral adjustment of fishes to release into a new habitat.
                      In Bardach, J.E., et al. (eds.), Fish behavior and its use in the cap-
                      ture and culture of fishes, p. 331-344. ICLARM (Int. Cent. Liv-
                      ing Aquat. Resourc. Manage.) Conf. Proc. 5, Manila, Philippines.
               Hiroshima Prefectureal Freshwater Fish Center
                    1983 Jumping test for investigating migrant behavior and the past life
                      of frys, p. 34. Kawate-cho 23-1, Shoubara, 727-12 Hiroshima [in
                      JpnJ-
               Iwamoto, M., and H Yamanaka
                    1986 Remarkable differences in rigor mortis between wild and cul-
                      tured specimens of red sea brearn Pagrus nwjor. Bull. Jpn. Soc.
                      Sci. Fish. 52:275-279.
               Keitoku H., H. Yasue, M. Tanaka, K. Hanaoka, Y. Nakasugi, and
                 N. Urasaki
                    1985 Artificial propagation of Sparid fish. Amin. Rep. Hiroshima
                      Farm. Fish. Assoc. 4:1-14 [in Jim].
               Kitajima, C., S. Fujita, F. Ohwa, Y. Yone, and T. Watanabe
                    1978 Improvement of dietary value for red sea brearn larvae of rotifers
                      Brachionus plicatilis cultured with Baker's yeast Saccharontyces
                      cerevisiae. Bull. Jpn. Soc. Sci. Fish. 45:469-471.
               Kitajima T., T. Arakawa, F. Oowa, S. Fujita, 0 Imada, T. Watanabe,
                 and Y. Yone
                    1980 Dietary value for red sea brearn. larvae of rotifer Brachionus
                      plicatilis cultured with a new type of yeast. Bull. Jpn. Soc. Sci. Fish.
                      46:43-46.
               Kobayashi, T., and K. Ohkuma
                    1983 On the device for stamina measurement of salmon fry, 'Sci.
                      Rep. Hokkaido Salmon Hatchery 37:41-44 [in Jpn.].
               Kuronuma, K., and K. Fukusho
                    1984 Rearing of marine fish larvae in Japan. IDRC-TS47e, Int. Dev.
                      Res. Cent., Ottawa, Ontario, Canada. 109 p.
               Maruyama, K.
                    1985 Experiment on quality determination of red sea brearn fry.
                      Annu. Rep. Jpn. Farm. Fish. Assoc. Fiscal Year 59:129-133.
                      Kaigan-dori 2-2-3, Chuou-ku, Koube 650 Hyougo [in Jpn.].
               Matsumiya, Y., H. Kanamaru, M. Oka, and M. Tateishi
                    1984 Morphometric comparison between artificially-released red sea
                      brearn and 0-age wild fish. Bull. Jpn. Soc. Sci. Fish. 50:1173-1178.




                                                                                                121






            Recent Progress                                                        In the last decade, with changes in social and economic con-
                                                                                   ditions, including the imposition of 200-mile territorial waters
            in Artificial Pronagation                                              by many countries, the roles of sea-fanning and aquaculture
                              0                     K' __rp                        have become more important in the coastal fisheries of Japan.
            of Marine Species for                                                  In this connection, considerable efforts have been directed
                                                                                   by governments and individuals to develop techniques of ar-
            Japanese Sea-farming                                                   tificial propagation, which are the basis of fish farming and
                                                                                   aquaculture. As a result, considerable progress has been
            and Aquaculture                                                        made in this field.
                                                                                     As illustrated in Figure 1, in the 7 years during 1977-84,
                                                                                   larval rearing of various species has steadily increased in
                                                                                   number (unpublished Prefectural and Fishery Agency re-
            AKIRA SUDA                                                             ports). In 1984 production of juveniles was attained in 32
            Japan Sea Farming Association                                          species of fishes, 15 species of crustaceans, 21 species of
            Kanda-Ogawamachi, 2-12, Chiyoda-Ku                                     shellfishes, and 9 miscellaneous species. Production has also
            Tokyo, Japan                                                           increased in total numbers as well (see Figure 2): 3.8 times
                                                                                   for red sea bream Pagrus major, more than 40 times for
                                                                                   Japanese Rounder Paralichthys olivaceus, about 5 times for
                                                                                   blue crab Portunus trituberculatus, and 3.8 times for aba-
                                                                                   lones (Haliotis spp.). The production of Kururna prawns
                                                                                   Penaeusjaponicus and Yesso scallop Patinopecten yessoensis
                                                                                   had already attained high levels by the mid-1970s and in-
                                                                                   creased another 20% by 1984.
                                                                                     Production of juveniles in 1984, the latest year for which
                                                                                   data are available, is shown in Table I by type of utilization
                                                                                   and hatchery facility (Fishery Agency and Japan Sea Farm-
                                                                                   ing Assoc. 1986). Research on larval rearing is carried out
                                                                                   by the following facilities which play different roles in
                                                                                   production:
                                                                                     1 National (A) and local (B) governmental facilites mainly
                                                                                   address the basic, practical aspects of technical development.
                                                                                     2 Local governmental (B) hatcheries disseminate results
                                                                                   of technical developments to fishermen.







                                                                                       30 -






                                                                                       2G -






                                                                                       lo -







                                                                                          71                   80                    83
                                                                                                                  YEAR


                                                                                                             Figure 1
                                                                                   Yearly change in number of species in seed production, 19774;4.

                                                                             123







                                                                                                          3 Fishermens' association (C) and private (D) hatcheries
                                                                                                        produce seed for industrial operations.
                                                                                                        A great number of scallop seeds are produced exclusively
                                                                                                                   -C hatcheries on a commercial basis for restocking
                                                                                                        by group
                                                            s-Up                                        operations and aquaculture. Fingerlings of red sea brearn and
                                                                                                        Japanese flounder and Kuruma prawn seed are produced in
                                                                                                        many hatcheries of all classifications and are used in prac-
                           'o
                                                                                                        tical and experimental restocking operations as well as in
                                                                                                        industrial aquaculture. In aquaculture of these species, ar-
                                                        ... ...                                         tificially produced seeds are now contributing a larger share
                           2o-                                                                          of seed stock. Blue crabs are reared mainly by government
                           lo                                                                           (groups A and B) hatcheries, thus seed is not directed to
                                                                            ........ ....               aquaculture but to restocking operations of either a more
                                                                                                        practical or experimental nature. In the case of the Tiger puf-
                                                       so   EAR                                         fer Fugu rubripes, fingerlings are produced almost solely
                                                                                                        for aquaculture. Various technical problems are still unsolved
                                                    Figure 2                                            for other species, and government (A and B) hatcheries are
                           Yearly change in number of seeds produced, 19774;4.



                                                                                               Table 1
                                                                             Number (10) of seeds produced in 1984.

                                                                          Type of utilization                               Type of facilities

                                         Species                    Sea-farming        Aquaculture           A             B               C              D

                                         Herring                            570                              416            154
                                         Striped jack                         39               197             39               1                            196
                                         Yellowtail                       1,210                             1,210
                                         Jack mackerel                      257                              257
                                         Striped knifeJaw                   880                542                         1,338               54             30
                                         Japanese seabass                   521                  30                         551
                                         Three-line grunt                   811                              219            592
                                         Red-spotted grouper                  49                               49
                                         Black sea bream                  6,307               1,225                        6,562              177           793
                                         Red sea bream                  22,572               16,742         4,245        23,908            2,446          8,711
                                         Black rockfish                     717                150           717            145                 5
                                         Scorpionfish                       240                                             240
                                         Japanese flounder                8,483               5,264         2,567          6,845               87         4,188
                                         Common flounder                  2,972                                            2,972
                                         Tiger puffer                       757               1,622                        2,073                            306
                                         Kuruma prawn                   484,684            117,165         9(1,000      352,146           11,745        147,958
                                         Kuma prawn                       3,345                                            1,345           2,000
                                         Yoshi prawn                    35,927                                           33,093                           2,834
                                         Hanasaki kingcrab                  426                              426
                                         Mad crab                         1,053                             1,053
                                         Blue crab                      38,350                             121,350       23,944               316           740
                                         Abalones                       29,960                1,002                      26,572            1,813          2,397
                                         Homed turban                       367                   5                         372
                                         Japanese babylon                   749                                             745                 4
                                         Ark shell                        5,370               8,480                      13,340               500             10
                                         Pearl oyster                                       23,568                       12,740            5,028          5,800
                                         Noble scallop                                       2,104                         1,714                            390
                                         Baking scallop                     426                893                          426              893
                                         Yesso scallop                1,777,710          1,490,093                                     3,267,803
                                         Clam shell                       1,241                                            1,241
                                         Sea urchins                      4,279                  70                        4,025             324

                                         Group A: National facilites (National Research Institute of Aquaculture and Japan Sea Farming Association)
                                         Group B: Local governmental hatcheries
                                         Group C: Fishermen's association hatcheries
                                         Group D: Private hatcheries


                                                                                                  124









                                              Table 2
                 Efficiencies of rearing techniques represented by survival raft and                                                              RED SEABFIEAM
                   number of seeds per cubic meter at the end of production.

                                          Size of        Survival       Number of
                                            seed           rate             seed                     so
                 Species                   (nun)                          per rn@

                 Yellowtail                   20          10              500
                 Red sea brearn               20          35-40         5,000
                 Three-line grunt             17          60            2,500                                           0
                                                                                                                     00    0     0   0,  *      * \'@
                 Black rockfish               30          60            1,690                                       %    ,   a
                                                                                                     10             %-   0 -9,     40.
                 Japanese flounder            20          60            5,000                                        VV    ;*
                 Herring                      50          60            3,000                                       0 00
                 Kururna prawn                13          70           18,000                    4               10                                       So..
                 Blue crab             Crab stage 1       25-40         6,000-10,000
                 Hanasaki kingcrab     Crab stage 1       60            7,500

                                                                                                                                             JAPANESE FLOUNDER




              involved in basic studies. For such groups, the development                            50
              of rearing techniques for species not previously cultured is
              a major responsibility.


              Recent views of                                                                                                       0
              rearing techniques                                                                                                  00

                                                                                                                                   %
              Efficiency                                                                                      j
                                                                                                              10                           so                   so..
              Nine selected species from the Japan Sea Farming Associa-                                                         TOTAL LENGTH
              tion are presented in Table 2 to show the efficiency of rear-
              ing techniques, represented by (1) survival rates throughout                                                   Figure 3
              the process of larval rearing and (2) number of larvae reared                   Fluctuation of survival rate (%) at the end of seed production among
              per cubic meter at the end of the process (Japan Sea Farm-                                          hatcheries and years, 1982414.
              ing Assoc. 1984). Survival rates are more than 30%, ex-
              ceeding 50% in many species. More efficient rearing of some
              species has been reported from some of the hatcheries in
              group B. Intensive mass production of juveniles with high                       raising particular species, including malnutrition of rotifers
              survival rates is becoming practical for red sea bream,                         and cannibalism of yellowtail. For these problems, answers
              Japanese flounder, Kuruma prawn, and blue crab in many                          have yet to be found.
              Japanese hatcheries, although some problems stiff remain.                          Another basic problem is that many more fingerlings are
                                                                                              needed to develop restocking operations, because the number
              Areas needing improvement                                                       produced by natural recruitment is greater than that of finger-
                                                                                              lings released. Also, we have no conclusive evidence of the
              One basic problem is that the survival rate of larvae fluc-                     ability of fingerlings to survive in the wild. This ability is
              tuates widely in every rearing operation even within the same                   essential for the success of restocking operations. The matter
              facility. Moreover, as is shown in Figure 3, survival rates                     will be observed further in the discussion on restocking of
              vary among years and hatcheries (Japan Sea Farming Assoc.                       red sea bream.
              1983, 1984, 1985; unpubl. Prefectural and Fishery Agency
              reports). Such fluctuations are due to many uncontrolled.
              causes such as quality of brood fish, conditions in the rearing                 An example of a
              tank, food quality, occurrence of disease, and cannibalism.                     restocking operation
                 Remarkable difficulties occur with some species for which
              mass production of fingerlings is becoming practical. For                       Currently, restocking operations on some commercial spe-
              example, body deformity with abnormal pigmentation fre-                         cies, e.g., Kuruma prawn, blue crab, scallops, red sea bream,
              quently occurs in flounder and flatfishes. Also, severe losses                  and flounder, are being undertaken in various areas in Japan.
              of larvae occur during the rearing of Kuruma prawn caused                       Among them, the operation on Yesso scallop resulted in a
              by baculovirus disease. Usually special problems occur in                       remarkable catch increase from 15 thousand tons in the

                                                                                         125












                                                             0















                                                                                                                                                0is,



                                                                                                                                                 0   0


                                                                                                                                              0 51


                                                      830
                                                                                                                                   0.39-
                                                                                                                                                      0

                                                                                                                                                --0-I.6.9
                                                                    No
                                                      2@6j
                                                                                                                                   .0.
                                                          ...........  0
                                                     50o       .574                                                                          .9
                                                                                                                                                          A--I
                                           -3


                                              @.175
                                   0
                                         661                                                                              .23

                                 1 03                                                                        0
                                                                                                                   2
                                                                                                                             A .... 2
                                                                                                                   I
                                   12 @2
                                 05






                                              Figure 4                                                                     Figure 5
                Number (103) of fingerlings of red sea bream released, by prefecture,         Ratio of number of fingerlings released to that of catch in number, by
                                                  1984.                                                                 prefecture, 1984.




                mid-1940s to more than 120 thousand tons in 1984 (Bureau                               C = R - FIZ              R'IC = R'I(R - FIZ)
                of Statistics 1985). As to other species, generally speaking,
                the effects of stocking have not yet proven statistically sigmfi-                            If R'IC <   1, then R'IR < FIZ < 1
                cant. Still, some local stocks, when combined with favorable
                natural conditions and the efforts of people involved, have                   where R     =   number of natural recruitment,
                been effectively restocked.                                                            R' =   number of fingerlings released,
                   Following is an outline of the red sea brearn restocking                            C  =   number of catch in a given year, including all
                operations,    as an example for discussion.                                                  age groups,
                   I Before release, fingerlings are kept for a short time in                          F  =   instantaneous rate of fishing mortality, and
                a pen at the location where they will be released to acclimatize                       Z  =   instantaneous rate of total mortality.
                them to the wild environment. Figure 4 illustrates the number
                of fingerlings released by each prefecture (Fishery Agency                    In many cases, the ratio is less than 1 which suggests more
                and Japan Sea Farming Assoc. 1986). To decide the scale                       fingerlings are necessary before the beneficial effects of the
                of release, it is important to know whether the amount of                     stocking operation are obvious (Fig. 5) (Bureau of Statistics
                release is large enough compared with that of natural recruit-                1985, Fishery Agency and Japan Sea Farming Assoc. 1986).
                ment. To arrange the key to this question, the ratio of the                     2 In Areas I and 2 in Figure 5, the ratio is fairly high,
                number of fingerlings released to the number caught locally                   especially in Area I where the catch actually increased recent-
                is given in Figure 5. When the ratio is less than 1, the amount               ly by about 20 % (ru 10 tons in weight) (Kanagawa Prefect.
                of release is expected to be less than natural recruitment.                   Fish. Exp. Stn. 1986). Here, the catch by sporfthing is

                                                                                        126








                estimated at 30-35 tons. If the latter estimate is taken into
                consideration, the increase in catch should be much more.
                In Area 2, surveys of fish markets indicated that about 10%
                of the catch came from fingerlings released (Hiroshima
                Prefect. Fish Exp. Sm. 1985).
                   3 The quality of fingerlings must be examined. It is
                expected that the difference in inherent abilities of finger-
                lings to survive the wild environment affects the efficiency
                of the operation. Recently, attempts have been made to grow
                larvae of red sea bream in an extensive rearing system in
                a large outdoor pond without an artificial diet. Some endur-
                ance tests on larvae grown in this way suggest that finger-
                lings reared in extensive culture survive in the wild better
                than those reared in intensive culture. This also suggests
                we can enhance the survival ability through the manner of
                rearing (Japan Sea Farming Assoc. 1985).
                   4 Cost of fingerlings is also an important factor for a prac-
                tical operation. In 1984, the cost for group-B hatcheries
                ranged between 3 and 50 yen, with a mean value of 13.5
                yen, per fish. Preliminary calculations of total expenditures
                to restock a fingerling, though still uncertain, suggest that
                it costs two to three times and more than the expenditures
                of rearng alone. The cost of fingerling production, together
                with other restocking costs, must be reduced if the opera-
                tion is to be more cost-effective. Thus, more improvements
                in rearing techniques are needed for the healthy development
                of a restocking program.


                Citations


                Bureau of Statistics
                    1985 Annual report of statistics on the production of fisheries and
                      aquaculture, 1984. Ministry of Agriculture, Forestry and Fishery.
                Fishery Agency and Japan Sea Farming Association
                    1986 Saibai-Gyogyo Shubyo-Seisan, Nyushu. Horyu Jisseki, 1984,
                      p. 373. [In Jpn., limited issue; temporary English tide: Materials
                      on the production and release of fingerlings for sea fanning, 1984.]
                Hiroshima Prefectural Fisheries Experiment Station et al.
                    1985 Kaiyusei-gyorui Kyodo-horyu-Jikken-chosa Jigyo. Setonaikai-
                      seibu-kaiiki Sogo-hokokusho, p. 123 [in Jpn.].
                Japan Sea Farming Association
                    1983 Nippon-Saibai-Gyogyo-Kyokai Jigyo-nenpo, 1982, p. 369. [In
                      Jpn.; temporary English tide: Annual technical report of Japan Sea
                      Farming Association, 1982.]
                    1984 Nippon-Saibai-Gyogyo-Kyokai Jigyo-nenpo, 1983, p. 296. [In
                      Jpn.; temporary English tide: Annual technical report of Japan Sea
                      Farming Association, 1983.]
                    1985 Nippon-Saibai-Gyogyo-Kyokai Jigyo-nenpo, 1984, p. 374. [In
                      Jpn.; temporary English title: Annual technical report of Japan Sea
                      Farming Association, 1984.]
                Kanagawa Prefectural Fisheries Experiment Station et al.
                    1985 Kaiyusei-gyorui Kyodo-horyu-Jikken-chosa Jigyo Sogo-
                      hokokusho, Taiheiyo-naka-ku, Madai-han, p. 51 [in Jpn.].










                                                                                            127








                                                              NOAA TECBNICAL REPORT NMIFS


                                                                         Guidelines for Contributors


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