Marine farming and enhancement proceedings of the fifteenth U.S.-Japan Meeting on Aquaculture, Kyoto, Japan, October 22-23, 1986

[From the U.S. Government Printing Office, www.gpo.gov]

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

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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
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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.

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.

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

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 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

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.

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.

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,

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.

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 (� 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 (� I SE) 24-hour survival of fish held in cages was
historic landing rates were less. 89.4- � 2.7 % in 1983 and 86.2 � 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,

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

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

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

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.

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.

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

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).

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

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

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

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

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.

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.
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Junk Publ., Netherlands. Leach, G.C.
Czeskleba, D.G., S. AveLallemant, and T.F. Thuemler 1920 Artificial propagation of sturgeon, review of sturgeon culture
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Dadswell, M.J. Bears Bluff Lab. 47:1-27.
1979 Biology and population characteristics of the shormose sturgeon, Magnin, E.
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1894 Recent experiments in sturgeon hatching on the Delaware River. Manea, G.
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1985 Epilogue: A perspective on sturgeon culture. In Binkowski, F.P., Marx, W.
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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)@
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Fo1z, D.J., D.G. Czeskleba, and T.F. Thuemler Serv., NOAA, Highlands, NJ, 69 p.
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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.
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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-
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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).

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

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.

60--

50--

With Stacking
40--

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.

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.].

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

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

@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

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

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

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.

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

-E

SPRING
AUTUMN
F
F

eK
Me

w A

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

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

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

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-

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.

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

0
0" '17.:
s'
N

44'N

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).

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.]

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

N-
E SU

'32 2

322

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 &

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.

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....

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

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.].

N<10
A I A A 100"@ N < 300
a A A 1. j1
33 AA-AAA-AA-A&A- A-A- 300-15 N M 3
AAN @ A& A A AAA A AA
IAA&AA AA A- AA AA&A& AAA A A
_ A A A A.* Ag.. A A A
'@.A.A A *A At" -AAA,A,AA.- A A
A-
A A @AAAAAA@AAAAAA- A. A A" A A A A&A A
A A& AA""& "' A""A"A -AA- AAA A A A
AAAA A A A A A
&AAA A4 A&A A A A AM
32- --"A AA&AA AA-A &&&A& AAAAAAA A -AA A-
A AAA AAkAA 4;A- A&AAA&& AAA,
A A AA&I __fft@ AA A A A
A 'AAA A A
&A.A A A. Ar AAAA A
A*
AA A AAA 616 A A. A
A
A A A AA A@I lt@l I A
31 A A
11 o AI-T-A"AI A
0 AA A A
A A. A A

30 - A

0 2 4 6 8 10 12 14
33 A 1983.5.IQ-6.11.
A 6.12.-6.20.
o 0 6.21.630.
'I, oo.. e
-A 7.1.-726.

32 acco

A Aooo A.
A
a 0
o
o
T jo
4 6 8 10

WATER TEMPERATURE OC

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

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.

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.

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

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.

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

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-

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-

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.

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.

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).

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).

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).

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

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.
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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-
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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,
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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
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physiology, vol. 9B, p. 351-403. Acad. Press, NY.

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.
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Liao (eds.), Reproduction and culture of milkfish, p. 126-139. 1988 Advances and future prospects in controlled maturation and
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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.
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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].
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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.

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

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

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)

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

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

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.

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.

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.

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

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.

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,

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

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

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.

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

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.
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Brachionus plicatilis making use of the secondary products of waste
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28:179-183 [in Jpnj.
Aihara, M. Mrano, K., and K. lErayama
1984 Fundamental plan (Official plan on seed production and nursery 1984 The effect of Tetraselmis tetrathele as a food on population
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1948 The intrinsic rate of natural increase of an insect population. 1%7 Mass culture of the rotifer fed baker's yeast. Saibai Gyogyo
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the rotifer Brachianus plicatilis fed with or without a laboratory- Maruyama, L, T. Nakamura, T. Matsubayashi, Y. Ando, and T. Maeda
cultured algae. Aquaculture 27:121-127. 1986 Identification of the alga known as "marine Chlorella" as a
Gilbert, J.j., and P.L. Starkweather member of Eustigmatophyceae. Jpn. J. Phycol. 4:319-325.
1977 Feeding in the rotifer Brachionus calyciflorus-I. Regulatory
mechanisms. Oecologia (Berl.) 28:125-131.

Matsuyama, M., and E. Shirouzu
1978 Importance of photosynthetic sulfar bacteria, Chromatium sp.
as an organic matter producer in Lake Kaiike. Jpn. J. Limnol.
39:103-111.
Okauchi, M., and K. Fukusho
1984 Food value of a minute alga, Tetrasebnis tetrathele, for the rotifer
Bracluonus phcatifis culture-1. Population growth with batch culture.
Bull. Natl. Res. Inst. Aquacult. 5:13-18.
Sakamoto, H., and K. Hirayama
1983 Dietary Effect of 7hiocapsa roseopersicina (Photosynthetic
Bacteria) onthe rotiferBrachionusplicatilis. Bull. Fac. Fish. Naga-
saki Univ. 54:13-20.
Satuito, C.G., and K. Hirayama
1986 Fat soluble vitamin requirements of the rotifer Brachionus
plicatilis. In Maclean, J.L., et al. (eds.) Proceedings, First Asian
Fisheries Forum, p. 619-622. Asian Fish. Soc., Manila, Philippines.
Scott, J.M.
1981 The vitamin B,2 requirement of the marine rotifer Brachionus
plicatilis. J. Mar. Biol. Assoc. U.K. 61:983-994.
Serra, M., and M.R. Miracle
1983 Biometric analysis of Brachionus plicatilis ecotypes from Spanish
lagoon. Hydrobiologia 104:279-291.
1985 Enzyme polymorphism in Brachionus plicatifis populations from
several Spanish lagoons. Int. Ver. Theor. Agnew. Limnol. Verb.
Limnol. 22:2991-2996.
Snell, T.W., and K. Carrillo
1984 Body size variation among strains of the rotifer Brachionus
plicatilis. Aquaculture 37:359-367.
Snell, T.W., and B.C. Winkler
1984 Isozyme analysis of rotifer proteins. Biochem. Syst. Ecol.
12:199-202.
Starkweather, P.L., and J.J. Gilbert
1977 Feeding in the rotifer Brachionus calyciflorus-11. Effect of food
density on feeding rates using Euglena gracilis and Rhodotorula
glutinus. Oecologia (Berl.) 28:125-131.
Suzuki, M.
1983 Taxonomical study on rotifers cultured for fry production.
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.

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

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.

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.

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.

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.

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

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.

Stn. A Stn- A Stn. D

300-

15- -200

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.

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

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.

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.

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.

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

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.

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

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

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

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

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.

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

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 � 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

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

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

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