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

                 FWS/OBS-82/10.85
                 AUGUST 1984

                 HABITAT SUITABILITY INDEX MODELS
                 AND INSTREAM FLOW SUITABILITY
                 CURVES: INLAND STOCKS OF
                 STRIPED BASS

                    x., o

                                                                7

                  . . . . .  .....

               QL        and Wildlife Service
               638
               .M678     Department of the Interior
               H37
               1984

                                               MODEL EVALUATION FORM

                       Habitat models are des  Igned for a wide variety of planning applica-
                  tions where habitat information is an important consideration in the
                  decision process.    However, it is impossible to develop a model that
                  performs equally well     in all   situations.   Assistance from users and
                  researchers is an important part of the model improvement process.          Each
                  model is published individually to facilitate updating and reprinting as
                  new information becomes available.      User feedback on model performance
                  will assist in improving habitat models for future applications.         Please
                  complete this form following application or review of the model.            Feel
                  free to include additional information that may be of use to either a
                  model developer or model user.     We also would appreciate information on
                  model testing, modification, and application,    *as well as copies of modified
                  models or test results. Please return this form to:

                                         Habitat Evaluation Procedures Group.
                                            or
                                         Instream Flow Group
                                         U.S. Fish and Wildlife Service
                                         2627 Redwing Road, Creekside One
                                         Fort Collins, CO 80526-2899

                  Thank you for your assistance.

                                                  Geographic
                  Species                         Location

                  Habitat or Cover Type(s)

                  Type of Application: Impact Analysis         Management Action Analysis
                  Baseline        Other

                  Variables Meas.ured or Evaluated

                  Was the species information useful and accurate?      Yes       No

                  If not, what corrections or improvements are needed?

                  Were the variables and curves clearly defined and useful? Yes      No

                  If not, how were or could they be improved?

                  Were the techniques suggested for collection of field data:
                       Appropriate?      Yes      No
                       Clearly defined? Yes       No
                       Easily applied?   Yes      No

                  If not, what other data collection techniques are needed?

                  Were the model equations logical? Yes       No
                                       Appropriate? Yes,-     No

                  How were or could they be improved?

                  Other suggestions for modification or improvement (attach curves,
                  equations, graphs, or other appropriate information)                                 rb

                  Additional references or information that should be included in the model:

                  Model Evaluater or Reviewer                           Date

                  Agency

                  Address

                  Telephone Number   Comm:                         FTS

                            J"

                                                                              FWS/OBS-82/10.85
                                                                              August 1984

                       HABITAT SUITABILITY INDEX MODELS AND INSTREAM FLOW SUITABILITY
                                    CURVES/ INLAND STOCKS OF STRIPED BASS

                                                       by

                                              Johnie H. Crance
                                    Instream Flow and Aquatic Systems Group
                                       Western Energy and Land Use Team
                                         U.S. Fish and Wildlife Service
                                                2627 Redwing Road
                                          Fort Collins, CO 80526-2899

              Lo

                                       Western Energy and Land Use Team
                                        Division of Biological Services
                                           Research and Development
                                           Fish and Wildlife Service
                                        U.S. Department of the Interior
                                             Washington, DC 20240

                  This report should be cited as:

                  Crance, J. H.   1984.  Habitat suitability index models and instream flow
                    suitability  curves:   Inland stocks of striped bass.      U. S. Fi sh Wi 1 dl .
                    Serv. FWS/OBS-82/10.85. 61 pp.

                                                     PREFACE

                     The Habitat Suitability Index (HSI) models and instream flow Suitability
                Index (SI) curves presented in this publication aid in identifying important
                variables that determine the quality of striped bass habitat.    Facts, concepts,
                and opinions obtained from published and unpublished reports, a Delphi panel
                of 18 striped bass experts/authorities,       and the Striped Bass Committee,
                Southern Division, American Fisheries Society, are synthesized and presented
                in a format that can be used for habitat impact assessment and development of
                management alternatives.

                     Use of the HSI models with the Habitat Evaluation Procedures (HEP) or the
                SI curves with the Instream Flow Incremental       Methodology (IFIM)     requires
                project scoping, including the setting of clear study objectives.           Armour
                et al. (1984) present comparisons of the uses of HEP and IFIM for impact
                assessment and helpful recommendations for selecting the method. most appro-
                priate for achieving study objectives.   If the HEP process is to be used, HSI
                model building techniques presented by the U.S. Fish and Wildlife Service
                (1981) and the general guidelines for modifying HSI models and estimating
                variables presented by Terrell et al. (1982) may be useful for simplifying and
                applying the HSI models to specific striped bass habitat assessment problems.
                Users of the SI curves for IFIM analyses should be familiar with the guide to
                stream habitat analysis (Bovee 1982) and the user's guide to the physical
                habitat simulation system (Milhous et al. 1984).

                     The HSI models and   SI curves are hypotheses of species-habitat relation-
                ships, and users should recognize that the degree of veracity of the models,
                curves, and assumptions  will likely vary according to geographical area, and
                the extent of the data base for the individual variables.         The model s and
                curves have not been tested against field data.     Therefore, the U.S. Fish and
                Wildlife Service encourages users of the models or curves to provide comments,
                suggestions, and field results that may help us increase the utility and
                effectiveness of this habitat-based approach to impact assessment.          Please
                send commments to:

                          Habitat Evaluation Procedures Group or
                          Instream Flow and Aquatic Systems Group
                          Western Energy and Land Use Team
                          U.S. Fish and Wildlife Service
                          2627 Redwing Road
                          Fort Collins, CO 80526-2899

                        Copies of the first printing (1984) of Habitat Suitability Index Models
                   and Instream Flow Suitability Curves: Inland Stocks of Striped Bass have been
                   expended.  Demand for the publication requires this reprinting.       I have taken
                   this opportunity to update and add some references that had not been published
                   at the time of the first printing.     No changes were made in the HSI models or
                   SI curves.

                                                                             Johnie H. Crance
                                                                             June 1986

                                                                                                             rb

                                                            iv

                                                         CONTENTS

                                                                                                       Page

                 PREFACE   .................................................................            iii
                 FIGURES  ........................................                                      vi
                 TABLES   ..................................................................            vii
                 ACKNOWLEDGMENTS    .........................................................          viii

                 INTRODUCTION    ............................................................             1
                 HABITAT USE INFORMATION     .................................................            2
                       General   ............................................................             2
                       Age, Growth, and Food     ..............................................           4
                       Reproduction    .......................................................            6
                       General Habitat Requirements      .......................................          6
                       Riverine Habitat Requirements      .......................................       11
                       Lacustrine Habitat Requirements      ....................................        16
                       Special Considerations     .............................................         18
                 HABITAT SUITABILITY INDEX MODELS       ........................................        18
                       Model Applicability    ................................................          18
                       Interpreting Model Outputs     .........................................         20
                       Model Description    ..................................................          24
                       Suitability Index (SI) Graphs for Model Variables        ..................      28
                 ADDITIONAL HABITAT MODELS      ...............................................         30
                 INSTREAM FLOW INCREMENTAL METHODOLOGY       ...................................        30
                       Suitability Index Curves Used in IFIM       ..............................       31
                       Availability of Striped Bass $I Curves for Use in IFIM         .............     31

                 REFERENCES    ..............................................................           46

                                                             v

                                                          FIGURES

                   Number                                                                            Page

                     1         Tree diagram illustrating relationships of habitat
                               variables and water quality in the riverine HSI model
                               for striped bass   .............................................       25

                     2         Tree diagram illustrating relationships of habitat
                               variables and water quality in the lacustrine HSI model
                               for striped bass   .............................................       26

                     3         SI curves for IFIM analyses of striped bass spawning
                               habitat  ...............................   .......................     33

                     4         SI curves for IFIM analyses of striped bass riverine
                               habitat for larvae   ...........................................       36

                     5         SI curves for IFIM analyses of striped bass riverine
                               habitat for egg incubation    ...................................      39       Cb

                     6         SI curves for IFIM analysis of striped bass riverine
                               habitat for juveniles    ........................................      41

                     7         SI curves for IFIM analyses of striped bass riverine
                               habitat for adults   ...........................................       44

                                                             Vi

                                                        TABLES

                Number                                                                              Paqe

                   1         Water temperatures associated with striped bass spawning        .....   12

                   2         The effects of water temperature on striped bass eggs       ........    13

                   3         Artificial data sets developed to illustrate how suitability
                             indices (SI), component indices (CI), and the habitat
                             suitability index (HSI) are calculated using the riverine
                             habitat variables and model equations      ........................     21

                   4         Artificial data sets developed to illustrate how suitability
                             indices (SI), component indices (CI), and the habitat
                             suitability index (HSI) are calculated using the lacustrine
                             habitat variables and model equations      ........................     22

                   5         Descriptions of, and suggested measurement techniques for,
                             variables used in riverine and lacustrine HSI model for
                             striped bass   .................................................        23

                   6         Availability of SI curves for IFIM analysis of striped
                             bass riverine habitat    ........................................       32

                                                          Vii

                                                       ACKNOWLEDGMENTS

                        Gratitude goes to the following biologists whose participation in the
                   Delphi exercise made development of this paper possible:            Jim Axon '   Kentucky
                   Department of Fish and Wildlife Resources; David Bishop, Tennessee Wildlife
                   Resources Agency; Joe Boone, Maryland Department of Natural Resources; David
                   Combs, Oklahoma Department of Wildlife Conservation; Charles Coutant, Oak
                   Ridge National Laboratory; Ed Crateau, U.S. Fish and Wildlife Service; Steve
                   Filipek, Arkansas Game and Fish Commission; Wayne Gustaveson, Utah Division of
                   Wildlife   Resources;    Reggie Harrell,     South   Carolina    Wildlife   and Marine
                   Resources Department; Ronald Lewis, Duke Power Company; Roger McCabe, Texas
                   Parks   and    Wildlife    Department;    Vernon Minton,     Alabama    Department of
                   Conservation.; Dale Mitchell, California Department of Fish and Game; Robert
                   Rees,  Georgia Department of Natural Resources; Donald Stevens, California
                   Department of Fish and Game;         Mike Van Den Avyle,     U.S.   Fish and Wildlife
                   Service; David Whitehurst, Virginia Commission of Game and Inland Fisheries;
                   and James Zuboy, National Marine Fisheries Service.

                        Thanks also goes to the Striped Bass Committee, Southern Division,
                   American   Fisheries Society.       The committee's interest, encouragement and
                   cooperation facilitated development of the paper.

                        Special thanks and acknowledgment go to Patrick Nelson for his collabora-
                   tion in the development of the Instream Flow Incremental Methodology section
                   of the paper.

                        The cover illustration was prepared by Jennifer Shoemaker.             Cathy Short
                   provided editing.     Word processing was by Dora Ibarra, Carolyn Gulzow, and
                   Madeline Sieverin.

                                                             viii

                                      STRIPED BASS (Morone saxatilis Walbaum)

                INTRODUCTION

                      Habitat suitability information about striped bass and methods for apply-
                ing the information are needed for water resource planning and management
                where the species is of concern.        The purpose of this paper is to develop
                striped bass Habitat Suitability Index (HSI) models for use with the Habitat
                Evaluation Procedures (HEP) and Suitability Index (SI) curves for use with the
                Instream Flow Incremental Methodology (IFIM).        HEP, which was first developed
                in 1976 (U.S. Fish and Wildlife Service 1980), is being applied Nationwide in
                both the public and private sectors (Schamberger and Krohn 1982) and is the
                most widely used evaluation technique by the U.S. Fish and Wildlife Service's
                Division of Ecological Services (Hardy 1981).        IFIM, which became operational
                in 1978 (Bovee and Milhous 1978; Stalnaker 1978), was initially used for
                assessment of the effects of stream flow regimes on fish communities in streams
                in the western portion of the United States.       It is now being used Nationwide
                for evaluating stream habitats and developing management recommendations and
                mitigating alternatives.      There are    several   similarities    and   differences
                between the outputs and recommended uses of HEP and IFIM.(Armour et al. 1984).
                HEP is a generalized technique for use in terrestrial and aquatic habitats.
                IFIM is a specialized method designed for flowing water only.

                      Literature on striped bass is broad, resulting from over a century of
                investigations about a      species that is generally characterized as being
                anadromous and is of great interest and importance to sporting, commerical ,
                and scientific interests alike.      A conservation measure for the fishery was
                enacted as early as 1639 (Pearson 1938).         Fish culturists began attempts to
                propagate the species by the early 1880's (Worth 1884) in hopes of increasing
                its abundance in estuarine and riverine habitats.          Freshwater reservoirs in
                New Jersey were stocked with striped bass as early as about 1935 (Surber
                1958).   Early reports on the life history of the striped bass (Scofield 1931;
                Pearson 1938; Merriman 1941; Raney 1952; Rathjen and Miller 1957), recent
                bibliographies (Pfuderer et al. 1975; Rogers and Westin 1975; Horseman and
                Kernehan 1976), and recent synopses (Westin and Rogers 1978; Hardy                1978;
                Setzler et al. 1980) are excellent sources of information about the species.
                The Striped Bass Committee, Southern Division, American Fisheries Society,
                identifies special study needs for striped bass, synthesizes information about
                introductions of the species into inland waters, and serves as a clearing
                house for information about striped bass in the southeastern United States.

                      Even though the striped bass has been studied under a variety of labora-
                tory and field conditions, there is a       dearth of published information about

                   the physicochemical , biological, and hydrological parameters that limit the
                   species in either lacustrine or riverine habitats.       Where data are inadequate
                   to develop SI curves for a species, opinions or best estimates of experts on
                   the species can be used to develop the curves.        However, opinions of experts
                   on a question may differ, resulting in problems in deciding which opinion
                   gives the best estimate.      Generally, the consensus of a group of experts
                   provides a more accurate response to a question than the response of a single
                   expert (Fusfeld and Foster 1971).      The Delphi technique, a method for devel-
                   oping a consensus among experts (Linstone and Turoff 1975; Zuboy 1981), was
                   used to obtain opinions from 18 striped bass experts/authorities on the vari-
                   ables that determine habitat suitability for various life stages of striped
                   bass,  the general    relationships between habitat       suitability    and   certain
                   important variables, and the general contents of this paper.        Summaries of the
                   steps used and results obtained from the Delphi technique were presented by
                   Crance (1985).

                        Terminology and criteria describing life stages of striped bass used in
                   this publication are as follows.       The egg stage begins with fertilization,
                   ends at hatching, and includes embryonic development. The larval stage begins
                   with hatching, ends at completion of fin formation, and includes yolk-sac,
                   finfold, and post-finfold larvae.      The juvenile stage begins on completion of
                   fin formation (when the fish takes     on the general appearance of mature fish)
                   and ends at sexual maturity.       The adult stage begins at sexual maturity and
                   lasts until the fish dies.     The spawning adult stage begins when the mature
                   adult initiates spawning runs and ends when spawning is completed.         Fingerlings
                   are young juveniles, about 2.5 to 10 cm (1 to 4 inches) long.

                   HABITAT USE INFORMATION

                   General

                        Striped bass are tolerant of a variety of environmental conditions. They
                   are found in marine, estuarine, riverine, and lacustrine habitats, depending
                   on individual stocks, life stage, environmental variables, transplantations,
                   and access to suitable spawning areas.

                        The Atlantic Coast range of the striped bass extends from the St. Lawrence
                   River in Canada (Magnin and Beaulieu 1967) to the St. Johns River, Florida
                   (McLane 1955), and on the Gulf of Mexico coast from the Suwanee River, Florida,
                   to Lake Pontchartrain, Louisiana (Jordon 1884; Gowanloch 1933; Pearson 1938;
                   Raney and Woolcott 1955; Barkuloo 1961; Brown 1965; Smith-Vaniz 1968; McIlwain
                   1968).  Except for an occasional remnant population, native Gulf Coast striped
                   bass no longer occur in their historical range, other than a small population
                   in the Apalachicola River, Florida (Barkuloo 1961; Crateau et al . 1980, 1981;
                   Wooley and Crateau 1983; Wooley 1982).

                        The Pacific Coast range of the species, originally established with
                   transplants from the East Coast, now extends from Barkley Sound, British
                   Columbia, Canada, to 25 miles south of the California-Mexico border (Radovich
                   1961; Miller and Lea 1972).

                                                              2

                     The results of stocking striped bass in freshwater habitats were sum-
                marized by Surber (1958), Mensinger (1971), Bailey (1975), Gustaveson et al.
                (1980), Harper (1982), Whitehurst (1982), and Axon and Whitehurst (1985).
                Landlocked populations of this species complete their life cycle in freshwater
                habitats associated with Millerton Lake, California (Wydoski            and Whitney
                1979);  Santee Cooper Reservoir,      South Carolina (Scruggs and Fuller 1955;
                Scruggs 1957; Stevens 1958); Keystone Reservoir, Oklahoma (Mensinger 1971;
                Combs 1979); Kerr Reservoir, Virginia (Whitehurst 1982); the Colorado River
                and Lake Powell, Utah (St. Amant 1959; Gustaveson et al. 1980, 1984; Persons
                and Bulkley 1982); and Lake Texoma, Oklahoma/Texas (Harper 1982).

                     Adults of coastal stocks typically are found in bays and waters around
                sandy beaches and shores (Pearson 1932; Bigelow and Schroeder 1953) with some
                water current (Hubback 1927; Raney 1952).        They occur at depths from 0.6 m
                (2.0 ft) (Haddaway 1930) to 46 m (151 ft) (Nichols 1966).           Generally, only
                mature or almost mature adults are found in marine waters, where they usually
                are confined to the neritic zone no more than 6 to 8 km (3.7 to 5 mi) offshore
                (Bigelow and Schroeder 1953).        Adults from some coastal      stocks undertake
                rather extensive coastal migrations (Merriman 1941; Vladykov and Wallace 1952;
                Chapoton and Sykes 1961; Clark 1968), while movements of adults from other
                coastal  stocks are generally confined within estuaries or river systems
                (Scruggs and Fuller 1955; Raney 1957; Scruggs 1957; Clark 1968; Murawski 1969;
                Barkuloo 1970; Dudley et al. 1977) or limited mostly to rivers, deltas, and
                bays with some oceanic migrations (Talbot 1966; Chadwick 1967).

                     Mature adults typically exhibit annual spawning migrations and require
                rather specific riverine reproductive habitat.      Spawning sites may be located
                just above the tide (Bieglow and Schroeder 1953) to as far as 320 km (199 mi)
                upstream above   saltwater (Raney 1954), but are usually located within the
                first 40 km (25 mi) of a stream (Talbot 1966).        Spawning sites are generally
                characterized by rapids, boulders, and strong currents (Norny 1882; Raney 1952;
                Mansueti and Hollis 1963; Talbot 1966).       Eggs require suspension by currents
                for good survival and successful hatching (Stevens 1966; Talbot 1966; Bayless
                1968).

                     Adults   generally   return   to  feeding grounds in open water areas of
                estuaries or reservoirs after spawning.      However, Dudley et al. (1977) found
                that adults moved as far as 301 km (187 mi) upstream from the spawning area
                immediately after spawning and remained in riverine habitat at least 4 months.
                The tendency for the species to be more riverine in southern portions of its
                range is also supported by Raney (1952), Raney and Woolcott (1955), Barkuloo
                (1967), and Wooley and Crateau (1983). Adults landlocked in reservoir systems
                exhibit variable migration and distribution patterns.

                     Temperature has been reported to be a directive factor in habitat selec-
                tion for juveniles and adults in some reservoirs (Coutant 1978, 1980; Schaich
                1979; Waddle 1979; Coutant and Carroll 1980; Cheek 1982; Cheek et al. 1985;
                Moss 1985).    Eggs generally hatch in riverine habitat, initial growth and
                development of larvae take place in the stream, and subsequent growth and
                development of larvae, juveniles, and adults occur in lacustrine habitat.
                Most landlocked stocks do not have access to suitable riverine habitat for
                reproduction and are sustained by stocking larvae or fingerlings.              Bailey

                                                          3

                    (1975) reported that striped bass survived "successfully" after being stocked
                    in reservoirs where the annual range of temperature was 0 to 34' C (33 to
                    93' F), total hardness was 10 to 375 ppm, turbidity was 1.5 to 170 JTU, and
                    the pHwas 5.5to9.1.

                    Age, Growth, and Food

                         Merriman (1941), using the scale analysis method, estimated that a 29.5 kg
                    (65 lb) striped bass was 29 to 31 years old.        There are historic accounts of
                    striped bass weighing 30 to 57 kg (66 to 126 lb) (Smith 1907; Bigelow and
                    Welch 1925; Walford 1937; Merriman 1941).

                         Growth, food habits, and development rates of striped bass vary widely,
                    depending on environmental and other conditions (Setzler et al. 1980).
                    Mansueti (1958) gave a detailed account of the egg, larva, and young arti-
                    fically spawned and hatchery-reared in water 16.7 to 17.21 C (62 to 631 F).
                    Eggs hatched 36 to 48 hours after fertilization.

                         The duration of the larval       stage ranges from about 23 days at 24' C
                    (75.2' F) to 68 days at 151 C (59.01 F) (Rogers et al . 1977).          A range of 18
                    to 21' C (64.4 to 69.8' F) appears to be optimal for growth from hatching
                    through the yolk-sac stage.

                         The yolk-sac stage lasts 3 to 15 days (Mansueti 1958; Albrecht 1964;
                    Doroshev 1970; Eldridge et al. 1977; Rogers et al.          1977).   Mansueti (1958)
                    reported that newly     hatched larvae ranged from 1.9 to 3.7 mm TL; 10 to
                    15-day-old larvae were about 7.5   mm TL when the yolk-sac was fully absorbed.

                         Larvae generally form     mouth parts at about 2 to 4 days of age or at
                    lengths of 4.5 to 5.2   mm TL  (Mansueti 1958; Tatum et al. 1966; Doroshev 1970).
                    They begin feeding at about     5 to 8 days of age and 6 to 8 mm TL (Doroshev
                    1970; Humphries and Cumming 1973). Food availability during the first several
                    days of feeding is a critical factor influencing survival of larvae (Miller
                    1977; Setzler et al. 1980; Cooper and Polgar 1981; Eldridge et al. 1981).

                         Pond-reared striped bass up to 10 mm TL generally prefer nauplii of
                    copepods and cladocera (Sandoz and Johnston 1966; Humphries and Cumming 1972).
                    They shift to larger zooplankton and microinvertebrates (Humphries and Cumming
                    1972), mainly copepods supplemented by cladocera and insects (Harper et al.
                    1969; Harper and Jarman 1972), at 10 to 30 mm TL.         In ponds with an abundance
                    of small forage fish, striped bass (at 30 to 60 mm TQ ate fewer copepods and
                    more cladocerans and insects (Harper et al. 1969).          At 60 to 69 mm TL, they
                    began feeding on forage fish,       and,   at 100 mm TL, @forage fish become an
                    important food item.

                         Juveniles usually are opportunistic feeders (Merriman 1941; Morgan and
                    Gerlach 1950; Johnson and Calhoun 1952; Raney 1952; Heubach et al.                1963;
                    Stevens 1966; Hester and Stevens 1970; Ware 1971; Manooch 1973; Boynton et al.
                    1981).  Utilization of fish in the diet of young-of-the-year striped bass
                    probably depends on the availability of a suitable forage fish at the proper
                    time and location (Markle and Grant 1970).       Young-of-the-year striped bass in

                                                               4

                 the Sacramento and San Joaquin River estuary fed mainly on invertebrates
                 during the first     winter and spring, changing to a diet of small          f i sh the
                 following summer     (Stevens 1966).    Gomez (1970) studied the food habits of
                 young-of-the-year    in Canton Reservoir, Oklahoma, and found that crustaceans
                 and insects were     a very significant part of the diet of striped bass 50 to
                 80 mm TL, gizzard    shad (Dorosoma cepedianu ) larvae were consumed by striped
                 bass as early as 53 mm TL, and gizzard shad made up 15% of the diet of 66 mm TL
                 striped bass.    Morris and Follis (1978) reported that striped bass over 1-year
                 old had reduced growth rates as shad (Dorosoma sp.) declined in Lake E.V.
                 Spence, Texas.

                       Adults also tend to be opportunistic feeders (Merriman 1941; deSylva
                 1973), but landlocked populations usually select clupeids or soft-rayed fish
                 over other available food items.      Striped bass in the Santee-Cooper Reservoir,
                 South Carolina, fed heavily on mayfly nymphs during the spring months, but ate
                 clupeid fishes almost entirely for the remainder of the year (Stevens 1958).
                 Gizzard shad was the dominant food item for striped bass in Keystone Reservoir,
                 Oklahoma (Mensinger 1971; Combs 1978).       Ware (1971) found a preponderance of
                 threadfin shad (Dorosoma petenense) and gizzard shad in the diet of striped
                 bass 15 cm (6 inches) and larger from Florida lakes.          Threadfin shad was the
                 primary food item, both in frequency of occurrence and total volume, of adults
                 from the lower Colorado River (Edwards 1974) and Lake Powell             (Persons and
                 Bulkley 1982). In the Illinois River, Oklahoma, striped bass 5 kg (11 lb) and
                 larger fed heavily on rainbow trout (Salmo gairdneri) for the first week after
                 the trout were stocked but gizzard shad made up 75% of their diet by number
                 thereafter (Deppert and Mense 1979).     Threadfin shad and American eel (Anguilla
                 rostrata) were the major food items in stomachs of juveniles and adults from
                 the Apalachicola River, Florida (Crateau et al. 1980, 1981).         An abundance of
                 small threadfin shad was considered critical for rapid growth of striped bass
                 larger than 110 mm TL in Lake Powell (Gustaveson et al. 1980).

                  1    Adults may feed during spawning migrations (Morgan, and Gerlach 1950;
                 Trent and Hassler 1966; Persons and Bulkley 1982), but likely fast during
                 spawning (Woodhull 1947; Morgan and Gerlach 1950; Hollis 1952; Stevens 1966;
                 Trent and Hassler   1966; Manooch 1973).

                       Compared to   natural coastal stocks, striped bass introduced into rivers
                 and lakes likely    grow faster, attaining an average length of about 25.4 to
                 27.9 cm (10 to 11 inches) the first year and 43.2 to 45.7 cm (17 to 18 inches)
                 the second year     (Scruggs 1957;    Stevens   1-958; Mensinger 1971; Ware 1971;
                 Erickson et al.     1972).   Juveniles, initially introduced into the Colorado
                 River from California waters, grew an average of about 15.2 cm (6 inches)
                 during the first year; river-spawned individuals grew to a mean of about
                 20.3 cm (8 inches) their first year (Edwards 1974).         The mean fork length of
                 age I and II striped bass from the Apalachicola River, Florida, was calculated
                 to be 15.6 and 30.7 cm (6.1 and 12.1 inches), respectively (Crateau et al.
                 1981; Wooley and Crateau 1983).      The length of striped bass from the Atlantic
                 Coast at age I was rougMy 12 cm (4.7 inches) and about 22 cm (8.7 inches) at
                 age II (Merriman 1941).      After age IV to VI, females grow faster than males
                 (Robinson 1960; Mansueti 1961; Bason 1971).

                                                            5

                   Reproduction

                        Males may be sexually mature in 1 year; females in 3 years (Morgan and
                   Gerlach 1950; Lewis 1962; Ware 1971).          More commonly, however, males are
                   sexually mature as 2-year-olds (Raney 1954;           Mansueti   1956;    Tagatz   1961;
                   Mansueti and Hollis 1963; Ware 1971; Kohlenstein 1981) and females as 4- to
                   6-year olds (Scofield 1931; Vladykov and Wallace 1938; Merriman 1941; Jackson
                   and Tiller 1952; Lewis 1962).       The annual production of eggs increases with
                   age and size of the female, ranging from about 65,000 as a 4-year-old to
                   4,500,000 as a 13-year-old (Jackson and Tiller 1952).

                        Streams suitable as striped bass reproductive         habitat generally have a
                   large volume of swift, turbulent water flowing over a substrate of rock and/or
                   fine gravel (Pearson 1938; Raney 1952; Fish and McCoy       1959; Fish 1960; Mansueti
                   and Hollis 1963; Kornegay and Humphries 1976; Combs         1979).   The distance of
                   the spawning site upstream from the river mouth varies by location and from
                   year to year within the same river system.       Spawning occurs 171.1 km (106 mi)
                   upstream from the mouth of the Apalachicola River, Florida, (Crateau et al.
                   1980); 80 to 100 km (50 to 60 mi) above Santee-Cooper Reservoir, South Carolina
                   (Scruggs 1957);    48 to 64 km (30 to 40 mi ) above the headwaters of Kerr
                   Reservoir, Virginia (Neal 1976); and 70 to 150 km (43 to 93 mi) above Keystone
                   Reservoir, Oklahoma (Combs 1979).       Persons and Bulkley (1982) reported that
                   striped bass spawned in or near the mixing zone of Lake Powell, Utah, and the
                   Colorado River.    Gustaveson (1984) provided evidence of in-reservoir spawning
                   by striped bass in Lake Powell.

                        Spawning is apparently cued to a rise in temperature in late winter or
                   early spring (Hardy 1978) and also may be cued to the photoperiod (Crance
                   1985).  Spawning begins as early as mid-February or early March in             Florida
                   (Barkuloo 1961, 1970) and may last until early July (Raney 1954)               in some
                   locations, depending on latitude and other factors.         Dudley and Black (1978)
                   reported three spawning peaks during a season.

                        The low and high temperatures at which spawning occurred in the           Roanoke
                   River, North Carolina, during a 5-year period were 12.8* C (551 F) and         21.71 C
                   (71' F), respectively (Shannon and Smith 1968). The optimal spawning tempera-
                   tures were about 16.7 to 19.4' C (62 to 671 F).            These ranges approximate
                   temperature data associated with striped bass spawning reported by Calhoun
                   et al. (1950), Farley (1966), and Talbot (1966).

                        Eggs are deposited near the water surface (Merriman 1941; Raney 1952).
                   The incubation period is about 34 hours at 21' C (70' F) (Shannon and Smith
                   1968), 51.8 hours and 62 hours at 18' C (64.40 F) and 15.01 C (59.01 F),
                   respectively (Rogers et al. 1977), and about 70 to 74 hours at 14.4 to 15.6' C
                   (58 to 601 F) (Surber 1958).

                   General Habitat Requirements

                        Self renewing inland stocks of striped bass generally require two major
                   types of habitat:     (1) riverine habitat for reproduction; and (2) lacustrine
                   or estuarine habitat for foraging, growth, and development by the larvae,
                   juveniles, and adults.

                                                              6

                       Information about the relationships between striped bass habitat suit-
                 ability and a few variables is substantial, but information for many variables
                 is sparse. Available data indicate that dissolved oxygen concentration, water
                 temperature, and velocity are - the principal Yariables that limit riverine
                 habitat suitability for striped bass; dissolved oxygen concentration and water
                 temperature   are   the  principal   variables    that  limit   lacustrine    habitat
                 suitability.

                       Food. Food availability may not directly limit the suitability of repro-
                 ductive habitat because adults do not feed immediately before and during
                 spawning (Woodhull 1947; Morgan and Gerlach 1950; Hollis 1952; Stevens 1966;
                 Trent and Hassler 1966; Manooch 1973).       However, their feeding habits during
                 spawning runs are unclear.     Larvae do not feed until they are 5 to 8 days of
                 age (Doroshev 1970; Humphries and Cumming 1973) and may not begin to feed
                 until they reach lacustrine or estuarine habitat.

                       Availability of prey (zooplankton) during the first few days of feeding
                 is likely a critical factor influencing the survival of striped bass larvae
                 (Miller 1977; Cooper and Polgar 1981; Eldridge et al. 1981).           Miller (1977)
                 reported that a minimum of 1,864 zooplankters per liter is required by larvae
                 during   initial   feeding;   however,   striped bass   larvae begin feeding and
                 apparently survive in some waters in California, where average concentrations
                 of zooplankton are much lower (Crance 1985).      A zooplankton density of 4,000/1
                 or more was reported to be optimal for young juveniles.

                       Landlocked adults feed primarily on gizzard shad and/or threadfin shad
                 (Stevens 1958; Mensinger 1971; Ware 1971; Edwards 1974; Bailey 1975; Weaver.
                 1975; Combs 1978; Deppert and Mense 1979; Gustaveson et al. 1980; Persons and
                 Bulkley 1982). The quantity of forage fish required likely depends on several
                 interacting variables, including the size of the striped bass population to be
                 sustained and the presence of other species that eat shad or that are eaten by
                 striped bass.    An established population of striped bass has been maintained
                 in Arkansas waters where the clupeid standing crop average was as low as
                 22.4 kg/ha (20 lbs/acre), but a standing crop of about 84.1 kg/ha (75 lbs/acre)
                 or higher is probably optimal (Crance 1985).

                       Water flow. Diversions of instream flow may block spawning migrations or
                 alter water depth, width, velocity, and/or other variables to levels critical
                 for spawning and survival of eggs and larvae. Stable, high volume stream flow
                 and water velocity during the spawning season probably enhance suitability of
                 reproductive habitat by helping to stabilize the water temperature, facilitate
                 the migration of spawning adults, suspend eggs until hatching, and buoy larvae
                 until suspension can be maintained by swimming.        Streams suitable for repro-
                 ductive habitat generally are characterized as having large volumes of moving
                 water (Pearson 1938; Raney 1954; Fish and McCoy 1959; Mansueti and Hollis
                 1963; Turner and Chadwick 1972) and uniform flows (Fish and McCoy 1959). High
                 volume stream flow may result in the emigration of striped bass from the
                 receiving reservoir if the reservoir has a short retention time.

                       Simultaneously rising discharges and water temperatures may have resulted
                 in striped bass migrating upstream to spawning sites in the John H. Kerr
     IS          Reservoir system, while very erratic stream flows, with or without rising
                                                            7

                  temperatures, appearod to repel the fish (Neal 1976).         Fish and McCoy (1959)
                  concluded that a section of the Roanoke River became progressively more
                  attractive to striped bass spawners as sustained minimum flows increased above
                  157 m'/s (5,550 cfs) and that most of the spawners were driven out of the
                  spawning area when minimum river flow decreased to 110 ml/s (3,900 cfs).
                  Successful spawning in the Apalachicola River, Florida, was associated w'ith
                  years when water flows of 255 to 8,213 m'/s (9,000 to 290,000 cfs) occurred
                  (Crance 1985).

                       Suspended sediments and turbidity.       Reports indicate that striped bass
                  have a relatively high tolerance to silt-laden and turbid waters (Mansueti
                  1961, 1962; Talbot 1966) and that high concentrations of suspended sediments
                  likely do not affect the eggs or larvae (Schubel and Wang 1973).

                       Sediment levels up to 500 mg/l did not affect the hatching success of
                  eggs (Schubel and Wang 1973; Schubel and Auld 1974). However, sediment levels
                  of 1,000 mg/l significantly reduced hatching success (Schubel and Auld 1974;
                  Auld and Schubel 1978).     Levels over 100 mg/l delayed hatching several hours
                  (Schubel and Wang 1973). Morgan et al. (1973, 1983) concluded that hatch of
                  striped eggs was not significantly affected by suspended sediment concentra-
                  tions ranging from 20 to 2,300 mg/l, but embryo development was slowed signif-
                  icantly at concentrations above 1,300 mg/l.
                       The LC 50 concentration of suspended sediments for striped bass larvae was
                  4,850 mg/l at 24 h and 2,800 mg/l at 48 h (Sherk et al. 1975). The mortality
                  rate of yolk-sac larvae increased significantly when exposed to suspended
                  sediment levels of 500 and 1,000 mg/l for 48 to 96 h (Auld and Schubel 1978).

                       Turbidity may indirectly benefit striped bass because it reduces light
                  penetration (Crance 1985).     Intense light may be harmful to striped bass.         In
                  addition, gizzard shad and threadfin shad concentrate at times in warm, turbid
                  water and become more vulnerable as prey.

                       Salinity and total dissolved solids.       Farley (1966)    concluded that      no
                  significant spawning occurred during 1 3 and 1964 in areas of the Sacramento-
                  San Joaquin River systems in California where concentrations of total dissolved
                  solids (TDS) were above       180 mg/l.    In addition,    TDS concentrations over
                  180 mg/l prevented striped bass from migrating above Stockton, California, in
                  the San Joaquin River. Murawski (1969) noted that striped bass spawned in the
                  Delaware River where the TDS concentration was 180 mg/l or less.           Radtke and
                  Turner (1967) concluded that 350 mg/l TDS was the critical concentration for
                  blocking upstream spawning migrations.        However, prespawning adults did not
                  avoid 954 mg/l TDS in Keystone Reservoir, Oklahoma (Summerfelt and Moiser
                  1976), and adults migrated through waters in the Arkansas River tributary of
                  Keystone Reservoir where the TDS level was 303 to 1,920 mg/l to reach spawning
                  sites (Combs 1979).

                       Albrecht (1964) concluded that low salinity (920 to 948 mg/l chlorides)
                  enhanced egg and      larval   survival   and that moderate      salinity (4,595 to
                  4,740 mg/l chlorides) was not detrimental.      The idea that    striped bass larvae
                  do better in low salinity water than in fresh water is supported by Rathien

                                                             8

                 and Miller (1957), Tatum et al . (1966), Bayless (1972), Davies (1973), Shell
                 (1974), and Lal et al . (1977).        Rees (1977) found no overall difference in
                 hatching success. or fry survival among groups of eggs hatched at salinities
                 of 0, 1,000, and 3,000 mg/l at 18.9' C (66.1' F).          Morgan et al. (1981) noted
                 that the effect of salinity on the development of striped bass is complex and
                 that, although salinity does not directly influence perc.ent hatch of eggs,
                 there is a significant interactive effect of salinity and temperature on
                 percent hatch, as well as on percent survival of larvae.          Larvae held in water
                 with salinity levels of 3,000 to 5,000 mg/l and then stocked in earthen ponds
                 in Alabama, with the salinity level of the water between 3,000 to 8,000 mg/l,
                 survived well (Crance 1985).

                       Tagatz (1961) reported that juveniles survived abrupt transfers between
                 salt and fresh water at temperature differences from 12.8 to 21.11 C (55 to
                 70' F), but were not tolerant to transfers from fresh water to salt water at
                 7.2' C (45' F). Adults were tolerant of abrupt changes between salt and fresh
                 water at differences in temperature from 7.2 to 26.7' C (45 to 80' F).

                       pH. The tolerance range of larvae and young juvenile striped bass appears
                 to be about pH 6 to 10 (Bonn et al . 1976; Regan et al . 1968; Shannon 1968;
                 Bailey 1975) ; the optimum range i s about pH 7.5 to 8. 5 (Bogdanov et al . 1967;
                 Davies 1973; Bonn et al . 1976).       Rapid changes in pH can be lethal to young
                 juveniles (Tatum et al.       1966).    Regan   et al.    (1968)  reported    that    mass
                 mortality of larvae occurred within 4 hours after being subjected to a change
                 i n PH f rom 7. 5 to 9. 9.    Doroshev (1970) reported 100% mortality of larvae
                 subjected to a change of 0.8 to 1.0 pH units.             Combs (1979) concluded that
                 there was no relation between pH and striped bass          production in the Arkansas
                 River, Oklahoma, where the mean daily pH ranged            f rom 7. 3 to 8. 5.   The U.S
                 Environmental Protection Agency (1976) recommended a pH range of 6.5 to 9.0
                 for freshwater aquatic life but cautions that the          toxicity of some compounds,
                 such as cyanide, increases as the pH is lowered            and that. the toxicity of
                 ammonia may increase 10 times when the pH increases from 7.0 to 8.0.

                       Contaminant load. Quality criteria for freshwater aquatic life developed
                 by the U.S. Environmental Protection Agency (1976), a review of EPA's criteria
                 (Thurston et al . 1979), and quality criteria for water adopted by States are
                 useful references for determining contaminant levels acceptable for striped
                 bass habitats.     Stevens et al. (1985) attributed toxic substances as one of
                 the most likely causes of decline of striped bass in the Sacramento-San Joaquin
                 Estuary, California.

                       Physical barriers.     Dams or other physical barriers that prevent fish
                 passage may eliminate access to spawning habitat.            Fishways have not proven
                 satisfactory for striped bass (Talbot 1966).

                       Stream width.    Extremely narrow streams can prevent adult striped bass
                 from moving to spawning sites.        However, width was not considered to be an
                 important variable that determines riverine habitat suitability (Crance 1985).

                       Stream length.    If spawning occurs in riverine habitat, a minimum distance
                 from the spawning site to lacustrine habitat is requ            .ired (see section on

                                                              9

                   minimum habitat size).    This distance will vary, depending on climate, locale,
                   density of eggs, and other factors.

                        Depth.   The relationship of water depth to suitability of striped bass
                   habitat is unclear (Crance 1985).        A minimum depth of 0.46 m (1.5 ft) is
                   assumed to be needed for adults to swim upstream to spawning areas.              Areas
                   with depths of 1.8 to 2.1 ni (6.0 to 7.0 ft) may be needed to provide temporary
                   refuge from boat traffic and excessive current and sunlight.           Spawning has
                   been reported to occur in waters less than 1.8 m (6 ft) deep and at depths up
                   to 15.2 m (50 ft). A depth range of about 1.8 to 9.1 m (6 to 30 ft) is assumed
                   to be optimal for spawning.      Extreme depths are not conducive to turbulence,
                   which is usually associated with spawning areas.        Loss of deep-water habitat
                   may have been one of the reasons for the decline of striped bass in Chesapeake
                   Bay (Price et al. 1985).

                        If dissolved oxygen and water temperature levels are within suitable
                   ranges, depths selected by striped bass in lacustrine habitats are determined
                   to a large degree by food availability.      Stratified lakes with a mean minimum
                   depth less than about 6.1 m (20.0 ft) and unstratified lakes with a mean
                   minimum depth less than about 1.8 m (6 ft) are likely to be unsuitable lacus-
                   trine habitat for juveniles and adults during summer.        Juveniles are commonly
                   caught in seinable waters 0.6 to 1.8 m (2 to 6 ft) deep (Crance 1985).

                        Substrate.   The relationship of substrate to     suitability of striped bass
                   habitat is unclear (Crance 1985).     Substrate is probably not a limiting factor
                   except where eggs or larvae      settle to the bottom.       Substrate composed of
                   particles large and/or dense enough that excessive amounts do not become
                   suspended often is generally     considered most suitable for spawning and egg
                   incubation. However, spawning    occurs over mud/silt in some coastal streams in
                   Georgia and in Chesapeake Bay    and over peat and sand substrate in California
                   waters (Crance 1985).

                        Data presented by Van Den Avyle and Higginbotham (1979) indicated that
                   juveniles in a Tennessee lacustrine habitat preferred sand substrate during
                   October and November but showed no preference for substrate type during other
                   months.   Shoreline seining for juveniles in        Oklahoma reservoirs was most
                   productive over sandy substrate (Mensinger 1971; Harper 1982).

                        Cover.   The relationships between cover and suitability of striped bass
                   habitat is unclear (Crance 1985).     Adults and larvae likely use instream cover
                   for resting and protection.      Streambank cover (trees or vegetation) provide
                   shade, which may help to reduce excessive light penetration and buffer the
                   water temperature.

                        Larvae and juveniles in lacustrine habitat are commonly found over sandy
                   substrate in shallow water.    They may use cover, such as submersed vegetation,
                   for foraging and protection from predators.          Harper (1982) reported that
                   juveniles were found least frequently in vegetated coves.      Adults are sometimes
                   abundant  in   lacustrine   habitat   near submersed    islands or shoals,       large
                   boulders, brush, overhanging ledges, and/or old river channels.

                                                             10

                  Riverine Habitat Requirements

                        Principal variables that determine the suitability of riverine habitat
                  for striped bass are water temperature (V,), dissolved oxygen concentration
                  (V,), and current velocity (V,).

                        Water temperature (V,j.     Water temperature regulates the activities of
                  adults and the survival and development of eggs and larvae.

                        Spawning.   Adults usually initiate spawning runs when temperatures reach
                  15 to 19' C (59 to 62' F) (Raney 1952).        Both the initiation and duration of
                  spawning are temperature-dependent (Calhoun et al. 1950; Rathjen and Miller
                  1957), and sudden drops in water temperature may interrupt spawning (Calhoun
                  et al. 1950; Chadwick 1958; Mansueti amd Hollis 1963; Farley 1966; Combs
                  1979).

                        Kernehan et al. (1981) collected striped bass eggs in the vicinity of the
                  Chesapeake and Delaware Canal where water temperatures ranged from 8.4 to
                  29.0' C (47.2 to 84.2' F), but they noted that most of the larvae produced in
                  the area resulted from intensive spawning in water with temperatures of 13.5
                  to 18.0' C (56.3 to 64.4' F).    Other temperature extremes reported for spawning
                  were a low of 101 C (501 F) (Institute of Environmental Medicine 1973) and a
                  high of 26.50 C (79.7' F) (Combs 1979). More commonly, spawning occurs within
                  the range of about 12 to 23.90 C (54 to 750 F) (see Table 1).

                        Shannon and Smith (1968) did not observe spawning in the Roanoke River,
                  North Carolina, when water temperatures were below         12.8' C (55' F) or above
                  21.7' C (71' F).     McCoy (1959) reported a minimum spawning temperature of
                  about 151 C (591 F) and a maximum of about 221 C             (721 F).    Combs (1979)
                  reported that spawning began in the Arkansas River,         Oklahoma, when the water
                  temperature reached 15.5 to 18.51 C (59.9 to 65.131         F), slightly higher than
                  initial spawning temperatures observed by Rathjen          and Miller (1957), McCoy
                  (1959), Hollis (1963, 1967), Kornegay and Humphries         (1976), Marshall (1976),
                  and   Neal  (1976).    Stooksbury (1977)     noted that    striped bass     spawned in
                  J. Percy Priest Reservoir, Tennessee, at 15 to 171 C (59.0 to 62.60 F).              The
                  optimum temperature range for spawning appears to be about 17 to 20' C (63 to
                  681 F), based on reports by McCoy (1959) and Shannon and Smith (1968).
                  However, the optimum spawning temperature range for striped bass in the
                  Apalachicola River, Florida, appears to be slightly higher (Crateau et al.
                  1981).   The minimum and maximum temperatures for spawning are about 121 C
                  (541 F) and 241 C (751 F), respectively (Table 1).

                        @.U . The effects of temperature on hatching and incubation time are
                  listed in Table 2.     The lower and upper temperature limits for survival of
                  eggs and resultant larvae are about 12.0' C (53.6' F) and 22.00 C (72.01 F),
                  respectively. Eggs incubated at 21.0' C (70' F) hatched, and the fry survived
                  for 3 days (Shannon and Smith 1968). However, when the incubation temperature
                  nears 23.0' C (73* F) egg survival declines rapidly (Morgan and Rasin 1973),
                  and resultant fry will not likely survive (Shannon and Smith 1968).

                       Table 1. Water temperatures associated with striped bass spawning.

                       Temperature
                      0C            OF                    State                 Reference

                 Spawning occurred

                   10.0            50.0                   NY          Institute of Environmental
                                                                      Medicine (1973)
                   12.0  to 22.0   53.6 to 71.6           CA          Albrecht (1964)

                   12.2  to 21.0   54.0 to 70.0           VA          Tresselt (1952)

                   12.2  to 22.2   54.0 to  71.0          NJ          Murawski (1969)

                   12.8  to 21.7   55.0 to  71.0          NC          Shannon and Smith (1968)

                   14.4  to 20.6   58.0 to  59.0          NC          Kornegay and Humphries (1976)

                   14.4  to 22.2   58.0 to  72.0          NC          McCoy (1959)

                   14.4  to 23.3   58.0 to  74.0          VA          Neal (1976)

                   15.0  to 17.0   59.4 to  62.6          TN          Stooksbury (1977)

                   15.0  to 20.0   59.0 to  68.0          NJ          Rathjen and Miller (1957)

                   15.0  to 22.0   59.0 to  72.0          NC          Humphries (1966)

                   15.5  to 26.5   59.9 to  79.7          OK          Combs (1979)

                   16.1  to 23.9   61.0 to  75.0          FL          Crateau et al. (1980, 1981)

                   17.2  to 20.0   63.0 to  68.0          CA          Turner (1976)

                   17.0  to 23.0   62.6 to  73.4          GA          Dudley and Black (1978)

                 Spawning peak

                   17.0 to 20.0    62.6 to  68.0          NC          McCoy (1959)

                   18.6 to 19.1    65.5 to  66.4          FL          Crateau et al. (1981)

                 Optimum spawning range

                   16.7 to 19.4 62.0 to     67.0          NC          Shannon and Smith (1968)

                                                            12

                         Table 2. The effects of water temperature on striped bass eggs.

                      Temperature
                        OC (OF)                      Effect on eggs             Reference

                 10 (50)                           Did not hatch             Morgan,e.t al. (1981)

                 10.5 (51)                         Did not hatch             Morgan and Rasin (1973)

                 11.0 (52)                         Did not hatch             Morgan and Rasin (1973)

                 12 (53.6)                         Seldom survived           Rogers et al. (1977)

                 < 12.2 (54)                       Died rapidly              Barkuloo (1970)

                 12.8 (55)                         Survived                  Albrecht (1964)

                 14.4  to 15.5 (58 to 60)          Hatched 70-74 hours       Surber (1958)

                 15.6  (60)                        Hatched 58 hours          Shannon and Smith (1968)

                 16.7  to 17.2 (62 to 63)          Hatched 48 hours          Mansueti (1958)

                 17.9  (64.3)                      Hatched 48 hours          Pearson (1938)

                 21.0  (70)                        Hatched 34 hours          Shannon and Smith (1968)

                 > 22.2 (72)                       Died rapidly              Barkuloo (1970)

                 Approached 23.0 (73)              Mortality increased       Morgan and Rasin (1973)

                 22.2 (72)                         None survived in          Turner and Farley (1971)
                                                   salinities above
                                                   1000 ppm

                                                             13

                         According to Doroshev (1970) and Morgan et al . (1981), the optimum tem-
                   perature range for best survival of striped bass eggs is about 17 to 201 C
                   (62.6 to 68.0' F).      However, Rogers et al. (1977) reported that egg survival
                   was highest at 15 to 181 C (59 to 64.4' F). Bayless (1972) suggested that egg
                   survival through hatching was best at 16.7 to 18.21 C (62 to 651 F).                 Rogers
                   (1978) proposed a temperature of 18' C (64.41 F) as the physiological growth
                   optimum for embryonic development and 18 to 21' C (64.4 to 70.0' F)                      for
                   yolk-sac absorption.

                         Larval.   Rogers et al . (1977) reported that the mean time between hatching
                   and yolk absorption was 5.1 days at 21' C (69.8' F) and 8.3 days at 151 C
                   (59' F). The duration of larval development (finfold plus post-finfold state)
                   was about 24 days at 211 C (69.81 F) and 68 days at 15' C (59' F). Larvae may
                   live within a temperature range of 12.8 to 23.9' C (55 to 75' F), but high
                   mortality can be expected at 23.9' C (751 F)              and above (Albrecht 1964).
                   Temperatures below 101 C (50' F) and above 23' C (73.41 F) are apparently
                   lethal to larvae (Doroshev 1970).          Shannon and Smith (1968) reported 100%
                   mortality of newly hatched         larvae held at 23.3' C (741 F) for 70 hours;
                   whereas, 100% of the larvae held at 21.1' C (70' F) for 76 hours survived. An
                   optimal temperature range of 18 to 211 C (64.4 to 69.81 F) was reported for
                   yolk-sac larvae (Rogers et al. 1977; Rogers 1978).            Temperature ranges of 16
                   to 221 C (60.8 to 71.6' F) and 16 to 19' C (60.8 to 66.21 F) were reported to
                   be favorable for striped bass larvae by Bogdanov et al. (1967) and Doroshov
                   (1970), respectively.       Results of a striped bass         Delphi technique (Crance
                   1985) indicated that larvae survival was good at              temperatures as high as
                   24. 41 C (76' F) i n Al abama ponds, 25' C (77' F) i n        Chaptank River, Maryland,
                   and 25.6' C (78' F) in South Carolina ponds; the ideal range for larvae in the
                   Apalachicola River, Florida, was 18.3 to 22.20 C (65 to 720 F).                Dey (1981)
                   hypothesized that a sudden drop in water temperature from 15 to 121 C (59.0 to
                   53.60 F) in the Hudson River Estuary probably resulted in almost complete
                   mortality of striped bass larvae. Boreman (1983) supported this hypothesis.

                         Dissolved oxygen concentration CV,j.        The U. S.    Environmental Protection
                   Agency (1976) recommended a dissolved oxygen concentration of 5.0 mg/l as the
                   minimum level for maintaining good fish populations.                Price et al. (1985)
                   presented evidence for the working hypothesis that the decline of striped bass
                   in Chesapeake Bay has resulted,          in part, from limiting concentrations of
                   dissolved oxygen.

                         Adult.   Areas of the Delaware River have been eliminated as striped bass
                   spawning grounds due to low dissolved oxygen concentrations (Chittenden 1971a).
                   Adults avoided water of 44% or less saturation in laboratory tests (Meldrim
                   et al. 1974).    It is assumed that dissolved oxygen concentrations suitable for
                   egg   survival,   embryo development, hatching, and larval            survival also are
                   suitable for spawning adults.

                         Egg.  Reductions in dissolved oxygen from 5 to 4 mg/l adversely affected
                   the percent hatch of eggs and had a detrimental effect on larval survival
                   (Turner and Farley 1971).        Harrell and Bayless (1981) reported that normal
                   development of striped bass embryos required a dissolved oxygen concentration
                   2: 3.0 mg/l. Dissolved oxygen levels of 2.0 to 3.0 mg/l may have been respon-
                   sible for the absence of striped bass eggs in areas of the Delaware River
                   (Murawski 1969).
                                                                14

                         Larval.    Dissolved oxygen concentrations of 2.0 mg/l and less are
                   considered detrimental      to  striped bass larvae (Dorfman and Westman 1970;
                   O'Mally and Boone 1972).     Levels of 2.0 to 3.5 mg/l have been responsible for
                   the absence of eggs and larvae in the Delaware River (Murawski 1969; Chittenden
                   1971a).   Chittenden (1971b) concluded that larvae need a minimum level of
                   3.0 mg/l to survive.       A level of 4.0 mg/l may be too low for successful
                   reproduction (Talbot 1966).        Even moderate reductions in dissolved oxygen
                   concentrations (from 5.0 to 4.0 mg/1) may decrease the survival of eggs and
                   larvae (Turner and Farley 1971).

                         Current velocity (V,J.

                         Adult. Water current probably is an attractant for striped bass that are
                   preparing to spawn (Dickson 1958).

                         Egg.  Striped bass eggs are semibuoyant.        Without sufficient current, the
                   eggs slowly settle to deeper water or the bottom and may suffocate due to a
                   deficiency in dissolved oxygen (May and Fuller 1965).            Continuous suspension
                   and movement of eggs appear to be essential to survival and successful hatching
                   in streams    (Surber 1958; Fish and McCoy 1959; May and Fuller 1965; Barkuloo
                   1970).   Albrecht (1964) and Bayless (1968) demonstrated, in the laboratory,
                   that eggs not held in suspension could be hatched but success was limited.
                   Eggs kept on the bottom during incubation had a poor chance of survival. Eggs
                   probably hatched successfully in the absence of turbulent current in Lake
                   Powell, Utah, where the dissolved oxygen concentration was 13.2 mg/l at the
                   substrate surface where the eggs settled (Gustaveson et al. 1984).

                         A minimum current velocity of about 30.5 cm/s (1 ft/s) is required to
                   suspend striped bass eggs in freshwater (Albrecht 1964).          However, the absolute
                   minimum velocity required can be site and time specific, depending on the
                   density of the water and the eggs.          Water density varies with temperature,
                   salinity, and total dissolved solids.           Egg density varies with age and/or
                   condition of the female and other factors (Schrader 1979).               A velocity of
                   15 cm/s (0.5 ft/s) may keep eggs suspended once they become water hardened
                   (Crance 1985).

                         Surface water velocity in areas where striped bass eggs have been
                   collected ranged from 12.2 to 88.4 cm/s (0.4 to 2.9 ft/s) in Virginia streams
                   (Tresselt 1952),    18.3 to 88.4 cm/s (0.6 to 2.9 ft/s) in California waters
                   (Albrecht 1964), and 50.0 to 83.5 cm/s (1.6 to 2.7 ft/s) in the Arkansas
                   River, Oklahoma,   where striped bass spawned 3 consecutive years (Combs 1979).
                   Current velocity in the Roanoke River below Weldon, North Carolina, was about
                   49 cm/s, (1.6 ft/s) near a major spawning area for striped bass (Dickson 1958).
                   Spawning occurred in areas of the Santee River, South Carolina, where water
                   velocity was less than 29.9 cm/s (0.98 ft/s) (Crance 1985).               Velocities of
                   about 240 cm/s (7.9 ft/s) may create shears approachi'ng the damaging range for
                   eggs (Marcy 1971, 1973; Morgan et al. 1976).          It was reported that eggs have
                   been observed in'water with velocities up to 270 cm/s (8.9 ft/s) and that a
                   velocity of about 400 cm/s (13.1 ft/s) is likely the maximum for survival
                   Grance 1985).

                                                                15

                        Larval    Larvae have little chance for survival if water currents are
                  insufficient to keep them from settling to the bottom (Barkuloo 1970).             Newly
                  hatched larvae tend to settle to the bottom of an aquarium filled with un-
                  agitated water despite swimming efforts to remain near the surface (Pearson
                  1938; Mansueti 1958).     Larvae likely require currents or turbulence for up to
                  15 hours post-hatch (Meinz and Heubach 1978).            Tests conducted by Morgan
                  et al. (1976) indicated that eggs and larvae have about equal specific gravity.
                  It is assumed that a minimum current velocity of 30.5 cm/s (1 ft/s), which is
                  the velocity required to float eggs (Albrecht 1964), is necessary to buoy
                  larvae until suspension can be maintained by swimming.

                        Current velocities higher than the minimum required to buoy eggs or
                  larvae could be detrimental by moving eggs downstream into the slack water of
                  a reservoir prior to hatching or by carrying larvae into slack water before
                  they can maintain suspension by swimming.         High velocity also may result in
                  shear levels that damage eggs and/or larvae. Exposure of striped bass eggs to
                  a shear level of 350 dynes/cm' killed 36% of the eggs in 1 minute, 69% in
                  2 minutes, and 88% in 4 minutes; exposure of larvae to 350 dynes/cm' killed
                  9.3% in 1 minute, 30.0% in 2 minutes, and 68.1% in 4 minutes (Morgan et al.
                  1976).   Marcy (1971, 1973) and Morgan et al. (1976) presented information
                  which indicated that a water velocity of about 240 cm/s (7.9 ft/s) created
                  shears approaching the damaging range for striped bass eggs and larvae.

                  Lacustrine Habitat Requirements

                        Water temperature and dissolved oxygen concentration are the principal
                  variables that determine suitability of lacustrine habitat for striped bass.

                        Water temperature        V, and V,).     Temperature preferences of striped
                  bass likely vary by locale, apparently change with age and an increase in size
                  (Schaich 1979; Coutant 1980, 1983, 1985), and influence lacustrine habitat
                  selection by juveniles and adults (Waddle 1979; Coutant and Carroll                1980;
                  Cheek 1982).

                        Adult (temperature,          The lower avoidance temperature by adults in
                  Cherokee Reservoir, Tennessee, was about 18.5' C (65.01 F) (Schaich 1979).
                  This was near the lower avoidance boundary for adults in coastal waters
                  (Radovich 1963) but higher than temperatures of 13.9 to 17.20 C (57.0 to
                  63.01 F) in areas in the San Francisco Bay where many adults spend the summer
                  (Crance 1985).

                        Adults in Cherokee Reservoir avoided water above 251 C (77' F) (Waddle
                  1979; Schaich 1979); adults apparently avoided water temperatures of 24 to
                  251 C (75.2 to 77.0* F) in Watts Bar Reservoir,             Tennessee (Cheek 1982).
                  Merriman (1941) reported that adults avoided coastal waters above 25 to 271 C
                  (77 to 80.61 F).    Dudley et al. (1977) observed that adults in the Savannah
                  River, Georgia, avoided temperatures over 26' C (78.81 F).          Concentrations of
                  adults were found in areas of Lake Whitney, Texas, in temperatures ranging
                  from 27.5 to 29.0' C (81.5 to 84.21 F) when cooler water was available in the
                  lake (Crance 1985).

                                                             16

                       Summer habitat selected by adults in Tennessee Reservoirs indicates an
                  average occupied temperature near 20' C (680 F) when warmer, oxygenated waters
                  were available (Schalch 2979; Waddle 1979; Cheek 1982).         Adults were found to
                  occupy   cool-water   refuges    (21.0' C;   69.81 F)   in the Apalachicola River,
                  Florida, during summer while surface water temperatures rose to 31' C (87.8' F)
                  (Crateau   et al.   1981;   Wooley   and   Crateau   1983).    It  appears     that  the
                  temperature niche for adult striped bass in lacustrine habitat may vary by
                  several   degrees (Crance, 1985).      This may be due to a number of factors,
                  including experimental variability, differences among fish stocks, geographic
                  location, age of fish, and the ranges of water temperature and                 dissolved
                  oxygen concentration available to the fish.

                       Juvenile (temperature, VJ.        Juvenile    striped   bass   select     and  grow
                  optimally at higher temperatures than are optimal for eggs, larvae,            or adults
                  (Cox and Coutant 1981, 1985).       Juveniles can tolerate temperatures        from 3 to
                  341 C (37.4 to 93.21 F) (Davies 1970).          About 34.4 to 35' C (94        to 95' F)
                  appears to be the upper lethal temperature range (Loeber 1951; Dorfman and
                  Westman 1970).    Growth apparently ceases at about 33.5"C (92.3' F) (Cox and
                  Coutant 1981).    Otwell and Merriner (1975) reported the         greatest growth of
                  juveniles at 24' C (75.2' F), which is within the range of 23.0 to               26.01 C
                  (73.4 to 78.4' F) indicated as optimal for growth by Cox          and Coutant    (1981).
                  Kellog and Gift (1983) reported that 26.9 to 30.3' C (80.5        to 86.61 F)    was the
                  optimum growth temperature range for striped bass that were 8.7 mm and           28.9 mm
                  long at the stgart and end of the test period, respectively.           However, it was
                  reported that juveniles held in brackish water ponds in Alabama at               12 mg/l
                  salinity and 331 C (91.41 F) actively fed and grew well (Crance 1985).

                       Larval (temperature,            Temperature    requirements    of    striped   bass
                  larvae in 1-acustrine habitat are assumed to be equal to temperature require-
                  ments of larvae in riverine habitat.      However, once larvae reach the lacustrine
                  habitat, they are generally a few days older and are likely to survive and do
                  well at slightly higher temperatures than they do at a younger age in riverine
                  habitat.

                       Dissolved oxygen concentration               Dissolv6d    oxygen     concentration
                  requirements for all      life stages of striped bass are assumed to be equal
                  whether they occur in   lacustrine or riverine habitat.

                       Adult (dissolved    oxygen,__V21. Refuges most frequently occupied by adults
                  in Cherokee Reservoir, Tennessee, had 5 mg/l or more dissolved oxygen (Schaich
                  1979; Waddle 1979).

                       Juvenile (dissolved oxygen,      21.   Krouse (1968) observed no mortality of
                  juveniles (2.8 to 13.0 cm TL; 1 to 4.4 inches) after 72 hours exposure to
                  5.0 mg/l dissolved oxygen.       Mortality increased at 3.0 mg/l,         and no fish
                  survived at 1.0 mg/l.      Chittenden (1971b) concluded that about 3.0 mg/l at
                  16.01 C (60.81 F) probably represents the minimum oxygen concentration for
                  normal existence of juveniles and that 3.0 mg/l may be insufficient to maintain
                  optimum populations of the species.     Dorfman and Westman (1970) and Klyashtorin

                                                              17

                  and Yarzhombek (1975) concluded that 4.0 to 4.5 mg/l can be considered the
                  critical, concentration of dissolved oxygen for young striped bass at 22* C
                  (71.6- F).

                       Larval (dissolved oxygen, V,.). Egg and larval requirements for dissolved
                  oxygen are assumed to be the same for both lacustrine and riverine habitats.

                  Special Considerations

                       Riverine habitat having a high HSI may not produce striped bass larvae,
                  and a high HSI for lacustrine habitat does not necessarily indicate a high
                  standing crop of striped bass.     Numerous factors, including hatching success
                  and survival of fry, spillway escapement, amount and availability of suitable
                  forage, size and number of predators that feed on striped bass,              stocking
                  practices, and fishing pressure, can influence year-class size and abundance.
                  Forage species eaten by juvenile and adult striped bass also are utilized by
                  other prey species. The abundance of forage species is influenced by physico-
                  chemical variables, making their availability to striped bass uncertain.

                       High temperatures in the epilimnion and low dissolved oxygen concentra-
                  tions in deep, cooler areas of a reservoir may bring about an environmental
                  "squeeze" during warmer months, causing adult striped bass to seek refuge in
                  relatively small , spring-fed coves or in tailwater areas (Coutant 1978; Schaich
                  1979; Waddle 1979; Cheek 1982; Cheek et al . 1985; Matthews 198-5; Moss 1985).
                  The "squeeze" may temporarily greatly reduce the volume and area of suitable
                  habitat available to adults.       While "squeezed" in the refuge, adults are
                  highly vulnerable to parasites and diseases and to harvest by anglers.            In-
                  adequate food may result from increased competition for available forage, and
                  fish may quit feeding and die due to the undesirable environmental conditions.
                  Thermal stress and/or low levels of dissolved oxygen have been reported to
                  result in mortality of adults in freshwater reservoirs (Axon and Whitehurst
                  1985) but summer mortality is by no means universal (Mathews 1985; Mathews
                  et al. 1985).   Wooley and Crateau (1983) found that striped bass weighing 4.5
                  to 6.7 kg (9.9 to 14.8 lb), captured in coolwater refuges during the summer,
                  showed a significant weight loss since the previous spring.         However, adults
                  weighing less than 4.5 kg (9.9 lb) had gained weight throughout the summer.
                  Adult and subadult striped bass collected from summer (June) refuges had lower
                  condition factors than those collected during April-May (Moss 1985).

                  HABITAT SUITABILITY INDEX MODELS

                  Model Applicability

                       These models are not applicable to habitat overburdened with toxic
                  chemicals or heated effluents or to rap-idly fluctuating conditions, such as
                  sudden changes in water temperature or river discharge during the spawning
                  season.   If contaminants are suspected to affect habitat suitability, guide-
                  lines on quality criteria for water are available from State water quality
                  control agencies, the U.S. Environmental Protection Agency (1976), and Thurston
                  et al. (1979).

                                                            18

                      Geographic area.    The models generally are applicable to riverine or
                 lacustrine habitat of striped bass throughout the 48 conterminous States.
                 However,  the models may require modification for use          in  some localized
                 habitats.

                      Season. The riverine model is applicable during the spawning season; the
                 lacustrine model   is applicable during the period when habitat quality is
                 expected to be critical      for the   life stage under consideration.       Summer
                 requirements of striped bass may not be adequately addressed for shallow,
                 eutrophic, warmwater reservoirs or for coldwater lakes where winter ice or
                 freeze-over occurs for several weeks.     If a model is applied for a specific
                 life stage, the HSI obtained will apply only to the season or period when the
                 life stage of interest occurs.

                      Cover types.   The lacustrine model is applicable to permanent freshwater
                 reservoirs. The riverine model is most applicable to sections of streams that
                 are utilized or likely to be utilized as striped bass reproductive habitat.
                 This model   could be applicable to a few mainstem reservoirs where water
                 velocity and other requirements for spawning and hatching are within suitable
                 ranges or to riverine habitat that striped bass occupy for reasons other than
                 spawning, such as some estuarine streams.

                      Minimum habitat size. The minimum area of lacustrine habitat required to
                 sustain a population of striped bass has not been established.     The species is
                 a pelagic feeder and probably prefers relatively large,-deep, open water areas
                 that are capable of supporting a clupeid forage base.           The Striped Bass
                 Committee, American Fisheries Society, considers the minimum habitat size to
                 be 1,215 ha (3,000 acres) (Crance 1985). Successful striped bass fisheries
                 have been established in reservoirs ranging in size from 40.5 to 73,305 ha
                 (100 to 181,000 acres) (Bailey 1975).       The area and volume of lacustrine
                 habitat utilized by adults during the warmest period of the year may be reduced
                 greatly due to high temperatures in the epilimnion and low dissolved oxygen
                 levels in deeper and cooler areas, coupled with a cool temperature preference
                 by adults.   Depth might be a limiting factor in lacustrine habitat if adult
                 fish cannot retreat to a suitable depth to escape excessive light.

                      The minimum length of stream required for riverine      reproductive habitat
                 can be roughly estimated by calculating the product of       current velocity and
                 hatching time.   The minimum length of stream required      is about 52.6 km or
                 32.7 miles (48 h x 30.5 cm/s or 1 ft/s)       if eggs must float for 48 hours
                 (approximate time for hatching at optimum water temperature) before hatching,
                 a minimum current velocity of 30.5 cm/s (I ft/s) is required for egg flotation,
                 and eggs move downstream at current velocity.     However, this estimate may not
                 represent the actual minimum stream length required because:       (1) eggs do not
                 move at current velocity; (2) water temperature may vary enough between stream
                 sections to alter hatching time; (3) suspension of the newly hatched embryo
                 may be required for about 15 hours        post-hatch,   increasing   the   distance
                 required; and (4) the role of currents within reservoirs, especially headwater
                 -areas, is unknown.

                                                          19

                       Veri f i cati on 1 evel .Neither model has been field tested.      Hypothetical
                  data sets were generated (Tables 3 and 4) and used to test the assumptions,
                  that HSI's obtained by using the models are reasonable and acceptable.

                       Eighteen striped bass experts/authori ties, who participated in a Delphi
                  exercise to develop     striped bass habitat suitability information (Crance
                  1985), reviewed a draft of this paper.        The reviewers provided substantial
                  ideas and suggestions that were incorporated, where appropriate, into the
                  model building effort.

                       Field use of models.    The level of detail for a particular model applica-
                  tion depends on time, money, and accuracy constraints. Detailed field sampling
                  of all of the variables that affect striped bass habitat will provide the most
                  reliable and replicable HSI's.      Use of previously collected data for any of
                  the variables may result in satisfactory application of the models.          Tempera-
                  ture, dissolved oxygen, and stream velocity data required for the models are
                  likely to have been published or be available from natural resource agencies.
                  Suggested techniques for measuring model variables and references to consult
                  for more details are listed in Table 5.       Subjective estimates of any or all
                  variables can be made in order to reduce the amount of time required to apply
                  the model s.   When subjective estimates are used, they should be made or
                  confirmed by experienced striped bass experts.        Use of subjective estimates
                  decreases reliability and replicability and should be accompanied by appro-
                  priate documentation on the method of HSI determination and quality of the
                  data used in the models.

                  Interpreting Model Outputs

                       Initially, the objective is that the HSI's for striped bass habitat
                  obtained using the models are correlated with an expert's ranking.           Ideally,
                  HSI outputs would have a direct linear relationship to carrying capacity.
                  This relationship is assumed but has not been tested.

                       The proper interpretation of the model output is one of comparison.
                  Habitats with high HSI's would, on the average, be expected to have higher
                  standing crops of striped bass or the potential to support more striped bass
                  than those with a lower HSI. The correlation between population size and HSI
                  has not been tested.   Factors not included in the HSI models may have a signif-
                  icant effect on population size.

                       The models cannot be expected to discriminate among different habitats
                  with high resolution at this stage of development because they depend on
                  untested assumptions and known oversimplifications.       Interactions among model
                  variables and species both play a role in determining habitat suitability for
                  striped bass; however, these influences are not considered in the model.           It
                  is suggested that the HSI outputs be interpreted as indicators or predictors
                  of high (0.8   to 1.0), medium (0.5 to 0.7), low (0.2 to 0.4), or        unsuitable
                  (0.0 to 0.1)   striped bass habitat.    Neither model will provide an    HSI of 1.0
                  if any model   component is not within the optimum value for the         life stage
                  being considered.

                                                            20

                       Table 3. Artificial data sets developed to illustrate how suitability
                       indices (SI), component indices (C), and the habitat suitability index
                       (HSI) are calculated using the riverine habitat variables and model
                       equations.

                                                Data set 1     Data set 2      Data set 3     Data set 4

                       Variable                 Data      Si   Data      SI    Data      SI   Data      SI

                   Temperature (V,)
                        0C                      14.5    0.8    17.0    1.0     21.0    0.7    18.5     1.0

                   Dissolved oxygen (V,)
                        mg/l                      6.0   1.0      4.2   0.6      4.0    0.5      7.0    1.0

                   Current velocity (V,)
                        cm/S                    55.0    1.0    40.0    0.5     213.0 0.2      15.0       0

                   CWQ                                  0.8            0.5             0.2               0

                   HSI                                  0.8            0.5             0.2               0

                   CwQ    lowest SI    HSI

                                                              21

                      Table 4. Artificial data sets developed to illustrate how suitability
                      indices (SI), component indices (C), and the habitat suitability index
                      (HSI) are calculated using the lacustrine habitat variables and model
                      equations.

                                              Data set I     Data set 2      Data set 3     Data set 4

                      Variable                Data      SI   Data      SI    Data     SI    Data      SI

                 Temperature (V,)
                    'C (larval)               14.9    0.9    17.0    1.0     21.0   0.7     2i.5    0.5

                 Dissolved oxygen (VA
                    mg/l (larval)               7.0   1.0     6.0    1.0       5.0  1.0       4.0   0.5

                 Temperature (V,)
                    'C (juvenile)             21.5    0.9    20.0    0.8     30.0   0.5             0.4

                 Dissolved oxygen (V,)
                    mg/l (juvenile)             6.0   1.0     7.0    1.0       4.9  0.8       3.4   0.2

                 Temperature (V,)
                    IC (adult)                18.0    1.0    17.0    0.8     28.0   0.4     29.0    0.2

                 Dissolved oxygen (V2)
                    mg/l (adult)                5.5   1.0     4.4    0.7       4.0  0.5       2.5      0

                 Component SI

                    C larval                          0.9            1.0            0.7             0.5
                    C juvenile                        0.9            0.8            0.5             0.2
                    C adult                           0.9            0.8            0.4                0

                    C = lowest  SI for component
                    No overall  lacustrine HSI calculated
                    Component HSI = component C

                                                             22

                                                                                                                            4@

                                           Table 5. Descriptions of and suggested measurement techniques for variables
                                            used in riverine and lacustrine HSI models for striped bass.

                     Hab i tat     Variab I e        Variable description                 Suggested technique                    Reference source

                     Riverine          V         Average mean daily temper-           Existing data, literature, or         American Public Health
                         or                      ature at midafternoon:               field sampling of representa-         Association (1981); Theurer
                     lacustrine                  riverine habitat during              tive reaches of stream using          et al. (1984).
                                                 spawning; selected lacustrine        thermometers.
                                                 habitat during larvae develop-
                                                 ment ( I a rvae).
                     Riverine          V@        Minimum dissolved oxygen             Existing data,   I iterature, or      American Public Health
                         or                      concentration near sunrise:          field sampling  of representa-        Association (1981).
                     lacustrine                  riverine habitat during              tive reaches of stream using
                                                 spawning; selected lacustrine        the Winkler or   idometric
                                                 habitat throughout year              method and its modifications
                                                 (adults, juveniles, or larvae).      or electrometric methods.
                     Riverine          V3        Average mean daily current           Existing data, literature,            Boyer (1964); Carter and
                                                 velocity in water column:            or field measurements of              Davidian (1965); Smoot
             FIO                                 riverine habitat during              representative reaches of             and Novak (1968); Bovee
                                                 spawning.                            stream, using current meter.          and Milhous (1978).
                     Lacustrine        V4        Average mean daily water             Existing data, literature,or          American Public Health
                                                 temperature at midafternoon          field sampling of representa-         Association (1981).
                                                 in selected lacustrine habitat       tive areas of reservoir us-
                                                 during growing season (juve-         ing thermometers.
                                                 niles).
                     Lacustrine        V5        Average mean daily water             Existing data, literature, or         American Public Health
                                                 temperature at midafternoon          field sampling of representa-         Association (1981).
                                                 in selected lacustrine habi-         tive areas of reservoir using
                                                 tat during warmest months            Winkler or idometric method
                                                 (2.3 to 4.5 kg, or 5 to              and its modifications or
                                                 10 lb adults).                       electrometric methods.

                Model Description

                      The assumed  relationships among model variables, components, and the HSI
                for the riverine   model and the lacustrine model are illustrated in Figure 1
                and Figure 2, respectively.     The models are structurally simple and can be
                modified as needed for special       situations and as additional       information,
                including    results of  field  tests to develop specific utilization curves,
                becomes available.    The riverine model produces an HSI between 0 and 1 for
                overall riverine (reproductive) habitat quality. The lacustrine model produces
                an HSI between 0 and I for each of three life stages (adult, juvenile, and
                larvae)   in  reservoirs.   A positive relationship between HSI and carrying
                capacity is assumed.    However, the models are habitat models, not population
                models, and their ability to predict production or population levels of striped
                bass is unknown .

                      The suitability index (SI) graphs (see pages 29 and 30) included reflect
                the author's subjective integration of the literature, expert opinion, personal
                experience, and reviewer comments. They represent assumed functional relation-
                ships between a variable and habitat suitability for a particular life stage
                and should be regarded as tentative and open to modification.         Documentation
                of the assumptions and rationale for including variables in the models and for
                developing the SI curves for the variables follow.

                      Riverine model.   Suitability of riverine habitat for spawning adults,
                eggs and larvae is directly related to water temperature (VI), dissolved
                oxygen concentration (V,), and stream velocity (V,).
                                                                                                             CD
                      Temperature (V,).   Spawning generally occurs at temperatures near 181 C
                (65' F). Optimal survival and development of eggs and larvae occur within the
                range of 15 to 201 C (59 to 681 F).        Spawning, egg survival and hatching
                success, and survival and growth of larvae are reduced at temperatures outside
                this range.   Therefore, these three life stages were combined for the water
                temperature component of the model, and a single temperature SI graph provided
                to determine the temperature SI (SI1) for riverine habitat.,

                      Dissolved oxygen 02). No significant difference appears to exist in the
                dissolved oxygen requirement for adult, egg, and larval life stages or between
                riverine and lacustrine habitats.    Levels of 5 mg/l and above are optimal for
                these three life stages.    Spawning activities and survival of eggs and larvae
                are reduced when dissolved oxygen levels are below 5 mg/l.       The minimal level
                for normal development of eggs and embryos is about 3 mg/l.           Mortality of
                juveniles occurs at 3 mg/l, and no juveniles survive at I mg/l. It is assumed
                that air-saturated waters are optimal and that supersaturated waters are
                unsuitable. Adult, egg, and larval life stages were combined for the dissolved
                oxygen concentration component of the model, and a single SI graph provided to
                determine the dissolved oxygen SI (SIO for both riverine and lacustrine
                habitat.

                                                          24

                   Habitat variables              Suitability index           Life requisite             Life stage

                 Water temperature (VI)                  Sil -

                 Dissolved oxygen
                   concentration (V2)                    S12 -                 Water quality           Spawning adult,          HSI
                                                                                                       egg, and larval

             N)
             U1

                 Current velocity (V3)                   S13

                                      Figure 1. Tree diagram illustrating relationships of habitat variables and
                                     water quality in the riverine HSI model for striped bass.

                      Habitat variables               Suitability index           Life requisite               Life stage

                    Water temperature (VI),
                      larval habitat                         S14-

                                                                                   Water quality                 Larval                HSI
                    Dissolved oxygen  (V2),
                      larval habitat                         S15

                    Water temperature (V4),
                      juvenile summer
                      habitat                                S16

                                                                                   Water quality                Juvenile               HSI

                    Dissolved oxygen (VA,
                      juvenile summer
                      habitat                                S17

                    Water temperature (V5),
                      adult summer
                      habitat                                SI8

                                                                                   Water quality                  Adult                HSI
                    Dissolved oxygen (V2),
                      adult summer
                      habitat                                Sig-

                                         Figure 2. Tree diagram illustrating relationships of habitat variables and
                                        water quality in the lacustrine HSI model for striped bass.

                       Velocity 03).     Newly hatched eggs require a minimum current velocity of
                 about 30.5 cm/s (1 ft/s) for flotation.        Water velocity less than 30.5 cm/s
                 0 ft/s) may buoy water-hardened eggs but eggs in all stages may occur in a
                 stretch of stream simultaneously.      Few, if any, eggs that settle to the bottom
                 will survive, presumably due to a deficiency in dissolved oxygen.         In addition,
                 few larvae survive if they are not buoyed during approximately the first 15 h
                 posthatch.    Assumptions relative to velocity are:        (1) the minimum velocity
                 required to suspe.nd eggs is about 30 cm/s (1 ft/s), and the same velocity is
                 necessary for successful       spawning and hatching;     (2) velocities of 50 to
                 122 cm/s (1.6 to 4.0 ft/s) are optimal; (3) suitability decreases as velocity
                 increases above 122 cm/s; and (4) velocities above about 400 cm/s (13.1 ft/s)
                 are unsuitable.    Streams must be of sufficient length to allow eggs to hatch
                 and larvae to attain self-buoyancy under the existing temperature, velocity,
                 and other conditions before reaching slack water in the reservoir.            Velocity
                 requirements for spawning, eggs, and larvae appear to be about equal, and
                 these three life stages were combined for the velocity component of the model
                 and a single velocity SI graph is provided to determine the current velocity
                 SI (SI,) for riverine habitat.

                       The variable in the riverine HSI model with the lowest SI is assumed to
                 be the limiting factor.      Therefore, overall riverine habitat suitability is
                 determined as follows:

                       HSI (riverine) = Lowest of the following variables: SI, SI,, or SI,

                       Lacustrine model.     Suitability    of   lacustrine    habitat    for    larvae,
                 juveniles, and adults is directly related to water quality, and water qua-lity
                 is primarily determined by water temperature and dissolved oxygen concentra@
                 tion.

                       Water quality determines habitat suitability independently for each life
                 stage component of the lacustrine model because temperature preferences of
                 striped bass change with age.

                       Larval. Survival and growth of striped bass larvae are generally optimal
                 within the temperature range of 15 to 20' C (59 to 68' F) and are reduced at
                 temperatures   below and above this range.          The temperature SI     (SIO     for
                 juveniles does not take into account that older larvae or larvae of all ages
                 in some habitats survive and do well in slightly higher temperatures.           There-
                 fore, the temperature SI curve for larvae may need to be modified to be useful
                 for the population of interest.

                       It is assumed that temperatures and dissolved oxygen levels suitable for
                 larvae in riverine habitat are suitable for larvae in lacustrine habitat and
                 that the SI graphs used to determine the temperature and dissolved oxygen SI's
                 for larvae in riverine habitat can be used to determine the SI'S (S14 and SIs)
                 for larvae in lacustrine habitat.       (See sections on temperature and dissolved

                                                            27

                  oxygen under Riverine Model.) Dissolved oxygen requirements are assumed to be
                  the same for all life stages. Therefore, the dissolved oxygen SI graph devel-
                  oped is for all life stages.

                       Juvenile.  Juvenile striped bass generally tolerate temperatures from 3
                  to 341 C (37.4 to 93.2' F) and select and grow optimally within the range
                  of 22.0 to 28.00 C (71.6 to 82.41 F).     Growth decreases outside this optimal
                  range and ceases at about 33.51 C (92.3' F).          Death occurs near 34.4' C
                  (940 F).

                       The dissolved oxygen SI (SI,) graph for juveniles is based on the assump-
                  tion that all life stages have equal dissolved oxygen requirements.

                       Adult.  Adult striped bass in reservoirs generally exhibit a temperature
                  preference of about 201 C (681 F) during summer months, but the optimum tem-
                  perature may vary from 18 to 241 C (64.4 to 75.20 F).         The lower avoidance
                  temperature boundary is near 161 C (60.80 F); the upper avoidance boundary is
                  about 251 C (77' F).     It is assumed that adults survive in reservoirs at
                  temperatures outside of these avoidance boundaries but that summer habitat
                  suitability decreases.    The temperature SI graph (SI.) developed for adult
                  striped bass in lacustrine habitats is assumed to represent preferences of
                  medium weight adults (5 to 10 lb).     It does not take into account temperature
                  preferences reported for adults in Lake Whitney, Texas, or the San Francisco
                  Bay area.  Also, the optimum range and the upper temperature range for SI = 0
                  may be too high for some reservoirs.    The temperature SI curve for adults may
                  need to be modified to be applicable to the specific size of striped bass and
                  the population of interest.

                       The dissolved oxygen   curve for adults (SI.) was based on the assumption
                  that all life stages of striped bass have the same dissolved oxygen require-
                  ments.

                  Suitability Index (SI) Graphs for Model Variables

                       This section contains suitability index curves and equations to quantita-
                  tively describe the relationships discussed in the previous sections.            The
                  curves provide a graphic representation of the relationships between various
                  measurements of habitat variables and habitat suitability.           The riverine
                  curves and equations can be used to produce an overall HSI for striped bass
                  reproductive habitat.    The lacustrine curves and equations can be used to
                  produce an HSI for each of the three life stages that occur in lacustrine
                  habitat.

                                                           28

                Habitat       Variable                                        Suitability graph

                Riverine (R),    V        Average mean daily
                Lacustrine (L)            water temperature
                                          at midafternoon:
                                                                     X   0.8-
                                          riverine habitat
                                          during spawning;
                                          lacustrine habitat             0.6-
                                          during larval
                                          development
                                                                         0.4-
                                          (larvae).

                                                                         0.2 -
                                                                     V)

                                                                         0.0-
                                                                            10    16    22    28     34

                                                                                        0C

                  R,L            V7.      Minimum dissolved              1.0-
                                          oxygen concentra-
                                          tion near surface:         X
                                                                     CD  0.8-
                                          riverine habitat
                                          during spawning;
                                          lacustrine habitat         >,  0.6-
                                                                     4-)
                                          throughout year
                                          (adults, juveniles,
                                                                         0.4-
                                          or larvae).

                                                                     V)  0.2

                                                                         0.0
                                                                             0   2    4    6    8   10

                                                                                         0C
                   R             V3       Average mean daily
                                          current velocity in            1.0-
                                          water column:
                                          riverine habitat           X   0.8-
                                          during spawning.

                                                                         0.6-
                                                                     4-)

                                                                         0.4-

                                                                         0.2-

                                                                         0.0
                                                                             0     62    124    186

                                                                                       cm/S

                                                         29

                     L              V4       Average mean daily              1.0-
                                             water temperature
                                             at midafternoon:
                                                                             0.8-
                                             lacustrine habitat
                                             during growing
                                             season (juvenile).              0.6-

                                                                             0.4-

                                                                        4)
                                                                             00 0' L
                                                                                10    16     22     28    34

                                                                                            0C

                     L              V5       Average mean daily              1.0-
                                             water temperature
                                             at midafternoon:            X
                                                                             o.8-
                                             lacustrine habitat
                                             during warmest
                                             months (adults,                 0-6-
                                             medium weight).
                                                                             0-4-

                                                                             0.2

                                                                             0.0
                                                                               10     16    22      28   34

                                                                                            0C

                  ADDITIONAL HABITAT MODELS

                       A habitat suitability index model developed by Bain and Bain (1982) is
                  available for coastal stocks of striped bass.       The riverine portion of their
                  model may be applicable to riverine habitat for inland stocks.

                  INSTREAM FLOW INCREMENTAL METHODOLOGY

                       Instream Flow Incremental Methodology (IFIM) is a process of stepwise
                  analyses used to assess instream flow problems (Bovee 1982).          The Physical
                  Habitat Simulation System (PHABSIM) model (Milhous et al. 1984), a component
                  of IFIM, is used to compute the amount of available instream habitat for life
                  stages of a species as a function of streamflow.

                                                            30
                                                                                   /A
                                                                                V1

                       The output generated by the PHABSIM component of IFIM can be used for
                 several IFIM habitat display and interpretation techniques, including:

                      .1.   Habitat Time Series.      Determination of impact of a project on a
                            species'   life stage habitat by imposing project         operation curves
                            over baseline flow time        series conditions     and   integrating    the
                            difference between the corresponding times series;

                       2.   Effective Habitat Time Series.       Calculation of the    habitat require-
                            ments of each life stage of a single species at           a given time by
                            using habitat ratios (relative spatial requirements of various life
                            stages); and

                       3.   Optimization.    Determination of flows (daily, weekly, and monthly)
                            that minimize habitat reductions for a complex of species and life
                            stages of interest.

                 Suitability Index Curves Used in IFIM

                       PHABSIM utilizes Suitability Index (SI) curves that describe the instream
                 suitability of the habitat variables most closely related to stream hydraulics
                 and channel structure (e.g., velocity, depth, substrate, cover, and tempera-
                 ture) for each major life stage of a given fish species (e.g., spawning, egg
                 incubation, larval, juvenile, and adult).         The Western Energy and Land Use
                 Team has designated four categories of curves and standardized the terminology
                 pertaining to the curves (Armour et al. 1984).        Category one curves are based
                 on literature sources and professional opinion.           Category two (utilization)
                 curves, based on frequency analyses of field data, are fit to frequency
                 histograms. Category three (preference) curves are utilization curves with the
                 environmental bias removed.       Category four (conditional       preferenc.e)   curves
                 describe habitat requirements as a function of interaction among variables.
                 The designation of a curve as belonging to a particular category does not
                 imply that there are differences in the quality or accuracy of curves among
                 the four categories.

                 Availability of Striped Bass SI Curves for Use in IFIM

                       The availability of SI curves for use in an IFIM analysis of striped bass
                 riverine habitat is summarized in Table 6.       The curves are category one curves
                 and should be considered for interim use until new information, such as data
                 obtained from field studies directed toward habitat suitability studies, is
                 available. The curves are based on a combination of.expert opinion, published
                 and unpublished reports, and the author's judgement.             The relationship of
                 velocity, depth, substrate, cover, and temperature to habitat suitability for
                 spawning, egg incubation, larvae, juveniles, and adults was given special
                 consideration throughout the curve development process (Figs. 3-7).                 Each
                 variable should be considered for each life stage, and variable SI curves not
                 included in this report may need to be developed if the variable/life stage is
                 important or an analysis of the effects of the variables on the habitat for a
                 life stage is a study objective.      SI curves for dissolved oxygen concentration
                 were not included because it was assumed that this variable is not a problem

                                                             31

                                        Table 6. Availability of SI curves for use with IFIM analysis of striped
                                        bass riverine habitat.

                     Activity/
                    life stage               Velocity               Depth             Substrate             Cover             Temperature

                  Spawning                 Use SI curve,         Use SI curve,        Curve not           Curve not          Use SI curve,
                                           Fig. 3.               Fig. 3.              necessary.          necessary.         Fig. 3.

                  Egg incubation           Use SI curve,         Use SI curve,        Use SI curve,       Curve not          Use SI curve,
                                           Fig. 4.               Fig. 4.              Fig. 4.             necessary.         Fig. 4.

                  Larval                   Use SI  curve,        Use SI curve,        Use SI curve,       Curve not          Use SI curve,
                                           Fig. 5,               Fig. 5.              Fig. 5.             available.         Fig. 5.
                  Juvenile                 Curve not             Use SI curve,        Curve not           Curve not          Use SI curve,
                                           available.            Fig. 6.              available.          available.         Fig. 6.

                  Adult                    Curve not             Use SI curve,        Curve not           Curve not          Use SI curve,
                                           available.            Fig. 7.              available.          available.         Fig. 7.

                                                                          1.0-
                          Coordinates                                 X
                                                                          0.8-
                         x              y
                     (ft/s)            (SO                                0.6

                        0.0            0.0
                        0.9            0.0                                0.4-
                        1.64           1.0
                        4.0            1.0                           V)   0.2-
                        7.0            0.2
                       13.2            0.0                                O.O__
                      100.0            0.0                                    0   1   2  3    4 5     6 7

                                                                                     Velocity (ft/s)

                         x              y                                 1.0-
                       (ft)
                                                                      x
                                                                      Q)  0.8-
                        0.0            0.0
                        1.4            0.0
                        6.0            1.0                                0.6-
                       30.0            1.0
                      100.0            0.0
                                                                          0.4-

                                                                          0.2 -
                                                                          0.0 0-        1     1'8   @4  30

                                                                                       Depth (ft)

                                                                              It is assumed that sub-
                                                                              strate is unimportant to
                                                                              or not used by striped
                                                                              bass for spawning and,
                                                                              therefore, a substrate
                                                                              SI curve for spawning
                                                                              is not necessary.

                         Figure 3. SI curves for IFIM analyses of striped bass riverine
                         spawning habitat.

                                                           33
                                                                                                         L

                                                                            It is assumed that cover
                                                                            in unimportant to or not
                                                                            used by striped bass for
                                                                            spawning and, therefore,
                                                                            a cover SI curve for
                                                                            spawning is not necessary.

                                                                         1.0-
                         Coordinates

                                                                     x
                        x              y                                 0.8-
                      (OF)            (SO
                        0.0           0.0                                0.6-
                      55.4            0.0
                                                                         0.4-
                      59.0            1.0
                                                                     M
                      68.0            1.0                           +)
                      73.4            0.0
                      100.0           0.0                           V)   M

                                                                         0  0
                                                                            35     50    65     80     95

                                                                                                 0
                                                                                   Temperature    F)

                                              Figure 3. (concluded).

                                                          34

                 when the temperature is within a suitable range.      If dissolved oxygen is an
                 important factor for riverine habitat suitability, the dissolved oxygen SI
                 curve component (V2) of the riverine HSI model can be used in an IFIM analysis
                 for the habitat of each life stage of striped bass.

                      Some of the SI curves in Figures 3 through 7 are the same as the S1
                 curves included for an HSI analysis.       The rationale for these curves was
                 included in the HSI section of this paper.    Some of the SI curves in Figures 3
                 through 7 were based primarily on the opinion of "participants in the Striped
                 Bass Delphi exercise (Crance 1985).

                      Spawning.  The SI curves for striped bass spawning (Fig. 3) are for IFIM
                 analyses of rilverine spawning habitat during the spawning season, which is
                 some time- between February and July, depending on the locale.    Spawning occurs
                 near the surface, and eggs incubate while suspended by water currents. There-
                 fore, spawning and egg incubation habitats are considered separately.

                      Velocity.   Adults have been observed to cease spawning and leave the
                 spawning site when water flow suddenly decreases.      Therefore, it is assumed
                 that water velocity is critical for spawning.      The precise suitability range
                 is unclear, but it is assumed to be similar or equal    to the velocity suitabil-
                 ity range for eggs and larvae.     The velocity curve developed as a component
                 (V,) of the HSI riverine model is the basis for the velocity SI curve for
                 spawning.

                      Depth. Assumptions used to develop the SI depth curve for spawning were:
                     the minimum suitable depth for unimpeded movement by adult striped bass is
                 0.45 m (1.5 ft); (2) depths of 1.83 to 9.1 m (6 to 30 ft) are optimum for
                 spawning; and (3) turbulence is associated with areas considered good striped
                 bass spawning habitat but extreme depths are not conducive to turbulent water.
                 Therefore, spawning habitat suitability likely decreases as depth increases
                 above some point, presumably about 9.1 m (30 ft), and continues to decrease
                 with increased depth, reaching medium suitability at about 15.2 m (50 ft) and
                 becoming unsuitable for spawning at 30.5 m (100 ft).

                      Substrate.  Striped bass spawn over a variety of substrates. Therefore,
                 substrate is not considered an important variable in determining spawning
                 habitat suitability.

                      Cover. It is assumed that striped bass do not utilize cover for spawning
                 and that a cover S1 curve for spawning is not necessary.

                      Temperature. The initiation and duration of spawning by striped bass are
                 temperature-dependent. The temperature curve developed as a component (V,) of
                 the riverine HSI model was the basis for the S1 temperature curve for spawning.

                      Egg incubation.   The SI curves for striped bass egg incubation (Fig. 4)
                 are for IFIM analyses  of riverine habitat where eggs incubate.    Normally, eggs
                 move with the current  and hatch in the water column in about 34 to 74 hours,
                 depending on the temperature.      The length of stream over which incubation
                 occurs varies, depending on water temperature, velocity, and other factors.

                                                          35

                          Coordinates
                                                                               0.8-

                         x                y
                      (ft/s)            (SO                                    0-6-

                        0.0             0.0                                    0.4-
                        0.9             0.0
                        1.64            1.0
                        4.0             1.0                                    0.2-
                        7.0             0.2
                        13.1            0.0                                    0.0--
                       100.0            0.0                                         0  1   2   3
                                                                                          Velocity (ft/s)

                                                                               1.0-

                         x                y
                        (ft)            (SO                                    0.8-

                        0.0             0.0                                    0.6-
                        1.4             0.0                               2@
                        6.0             1.0
                        30.0            1.0                                    0.4-
                       100.0            0.0
                                                                               0.2

                                                                               0.0
                                                                                    0    6   12    18    24    30

                                                                                              Depth (ft)

                                                                               1.0-
                   x                                          y           X
                (code)          Particle size                (SO               0.8-

                   1       Plant detritus/organic            0.1
                              material                                         0.6-
                   2       Mud/soft clay                     0.4
                   3       Silt (< 0.062 mm)                 0.6               0.4-
                   4       Sand (0.062 to 2 mm)              1.0
                                                                         4-J
                   5       Gravel (2 to 64 mm)               1.0               0.2-
                   6       Cobble/rubble                     1.0         V)
                              (64 to 250 mm)
                   7       Boulder (250 to 4,000 mm)         1.0               0 - 04--@- 1   1 -1   1  1   1
                   8       Bedrock (solid rock)              1.0                     1 2 3 4 5 6 7 8

                                                                                            Substrate

                         Figure 4. SI curves for IFIM analyses of striped bass riverine
                         habitat for egg incubation.

                                                            36

                                                                             It is assumed that cover
                                                                             is unimportant to striped
                                                                             bass egg incubation and,
                                                                             therefore, a cover SI
                                                                             curve for egg incubation
                                                                             is not necessary-.

                         Coordinates                                   1.0-
                                                                   x
                        x                                              0.8-
                                       y
                      (OF)            (SO
                                                                       0.6-
                        0.0            0.0
                      55.4             0.0
                                                                       0.4-
                      59.0             1.0
                      68.0             1.0
                      73.4             0.0                             0.2-
                      100.0            0.0

                                                                       0.0
                                                                            35   @O     65     80     95

                                                                                                0
                                                                                 Temperature     F)

                                              Figure 4. (concluded).

                                                          37

                        Depth.   The precise water depth crucial for egg        incubation is unclear.
                   However,   a depth SI curve was developed based on the assumptions that:
                   (1) depths less than 0.45 m (1.5 ft) are unsuitable for      egg incubation habitat;
                   and (2) depths of 1_83 m (6 ft) and over provide optimum     suitability,

                        Substrate. Eggs normally incubate while suspended in the water column by
                   currents.   Therefore, substrate type does not become a      limiting factor to egg
                   incubation except where eggs settle to the bottom.         If the eggs sink to the
                   substrate, the chances of survivial are greatly reduced, presumably due to
                   siltation and a deficiency in dissolved oxygen.         The substrate SI curve for
                   egg incubation was based on the assumption that siltation rates are higher,
                   dissolved oxygen concentration lower, and survival rates of eggs lower if the
                   dominate substrate type consists of particles smaller than sand.            Sand and
                   larger particles are assumed to be oRtimum substrate composition.

                        Cover.    It is assumed that cover is unimportant for striped bass egg
                   incubation and that a cover SI curve for egg incubation is not necessary.

                        Temperature.    Incubation of striped bass eggs is tempera tu re-dependen t.
                   The temperature SI curve for egg incubation is based on the temperature SI
                   curve developed as a component (V,) of the riverine HSI model.

                        Larvae.   The SI curves for striped bass larvae (Fig. 5) are for IFIM
                   analyses of riverine habitat where larvae are commonly found.

                        Velocity.    The velocity curve developed as a component (V,) of the HSI
                   model was the basis for the larval velocity SI curve.

                        Depth.   The depth SI curve for larvae was based on the same assumptions
                   as the depth SI curve for egg incubation.         It is assumed that equal depths
                   have equal SI's for larvae and eggs.

                        Substrate.    Newly hatched larvae have about the same density as eggs.
                   They require a current for suspension until bouyancy can be maintained by
                   swimming. It is assumed that equal substrate types have equal SI's for larvae
                   and eggs.

                        Cover.   It is assumed that larvae utilize potholes, rocks, rubble, over-
                   hanging vegetation (shade), and other cover forms for protection from predators
                   and excessive light and for resting.         However, no SI curve for cover was
                   developed because several methods are used to describe cover and there is a
                   sparseness of information on cover use by larvae.       A cover SI curve for larvae
                   should be developed if a complete IFIM analysis of larvae riverine habitat is
                   required.

                        Temperature.    The temperature curve developed as component V, of the HSI
                   model was the basis for the, larval SI temperature curve.

                      I Juvenile.    SI curves for striped bass juveniles (Fig. 6) are for IFIM
                   analyses of riverine habitat where juveniles are commonly found.          Only depth
                   and temperature SI curves are available for juvenile riverine habitat, and

                                                              38

                                                                        1.0-

                                                                        0.8-
                     Coordinates

                                                                        0.6-
                    x                y
                 (ft/s)            (SI)                                 0.4-
                   0.0             0.0
                   0.9             0.0                                  0.2 -
                   1.64            1.0
                   4.0             1.0                                  0.0
                   7.0             0.2                                      0   1   2  3   4   5   6  7
                   13.1            0.0
                  100.0            0.0                                              Velocity (ft/s)

                                                                        1.0-

                    x                y                             X
                                                                        0.8-
                   (ft)            (SO

                   0.0             0.0                             >    0.6-
                   1.4             0.0
                   6.0             1.0                                  0-4-
                   30.0            1.0
                  100.0            0.0                             4-)
                                                                   V)   0.2

                                                                        0 .0
                                                                            0    6    12   18    24 30

                                                                                      Depth (ft)

               x                                       y
           (code)          Particle size              (SO          x
                                                                        0.8-
               I      Plant detritus/organic           0.1
                        material                                   >-,  0-6-
               2      Mud/soft clay                    0.4
               3      Silt (< 0.062 mm)                0.6
                                                                   -0   0-4-
               4      Sand (0.062 to 2 mm)             1.0         ro
                                                                   4-)
               5      Gravel (2 to 64 mm)              1.0
               6      Cobble/rubble                    1.0              0.2-
                         (64 to 250 mm)
               7      Boulder (250 to 4,000 mm)        1.0
               8      Bedrock (solid rock)             1.0              0.0   1  2  3   4  5  6   7 8

                                                                                  Substrate type

                    Figure 5. SI curves for IFIM analyses of striped bass riverine
                    habitat for larvae.

                                                       39

                                                                             A cover SI curve for
                                                                             larval striped bass is
                                                                             not available. Informa-
                                                                             tion on the relationship
                                                                             of the variable to larval
                                                                             habitat suitability was
                                                                             insufficient to develop
                                                                             a curve.

                          Coordinates                                    1.0-

                         x              y                                0.8-
                       (OF)            (SO

                                                                         0.6-
                         0.0           0.0
                       55.4            0.0
                       59.0            1.0                               0.4-
                       68.0            1.0
                       73.4            0.0
                       100.0           0.0                          Ln   0.2

                                                                         0.0
                                                                             35     50    65      80    95

                                                                                                   0
                                                                                    Temperature    F)

                                               Figure 5. (concluded).

                                                           40

                                                                          A velocity SI curve for
                                                                          juvenile striped bass is
                                                                          not available. Informa-
                                                                          tion on the relationship
                                                                          of the variable to
                                                                          juvenile habitat suit-
                                                                          ability was insufficient
                                                                          to develop a curve.

                        Coordinates                                     1.0-

                                                                   x
                     x               y                             GJ   0.8-
                    (ft)            (SO
                     0.0            0.0                            >,   0.6-
                                                                   4-3
                     1.4            0.0
                     6.0            1.0                            -0   0.4-
                    30.0            1.0
                   100.0            0.0
                                                                   Ln   0.2

                                                                        0.0
                                                                            0    6    12   18    @4   30
                                                                                      Depth (ft)

                                                                          A substrate SI curve for
                                                                          juvenile striped bass is
                                                                          not available. Informa-
                                                                          tion on the relationship
                                                                          of the variable to
                                                                          juvenile habitat suit-
                                                                          ability was insufficient
                                                                          to develop a curve.

                     Figure 6. S1 curves for IFIM analyses of striped bass riverine
                     habitat for juveniles.

                                                       41

                                                                              A cover SI curve for
                                                                              juvenile striped bass
                                                                              is not available. Infor-
                                                                              mation on the relation-
                                                                              ship of the variable to
                                                                              juvenile habitat suit-
                                                                              ability was insufficient
                                                                              to develop a curve.

                           Coordinates                                  1.0-

                                                                    x
                          x              y                              0.8-
                        (OF)            (SO
                                                                    >,  0.6-
                          0.0            0.0
                        53.6             0.0
                        71.6             1.0                            0.4-
                        82.4             1.0
                        91.4             0.0                            0.2                            -
                        100.0            0.0

                                                                        0.0
                                                                             35   50     65     80    95
                                                                                                 0
                                                                                  Temperature     F)

                                                Figure 6. (concluded).

                                                            42

                they are based on scanty information.       SI curves for velocity, substrate, and
                cover need to be developed if a complete IFIM analysis of juvenile riverine
                habitat is required.

                      Velocity.   Insufficient information was available to develop a velocity
                SI curve for juveniles.

                      Depth. The depth SI curve for juveniles was based on the same        assumptions
                as the depth SI curve for adults [i e. , a minimum depth of 1.83 m        (1.5 ft) is
                required for unimpeded movement, and depths of 1.83 to 9.1 m (6 to 30 ft)
                provide optimum suitability].      The curve does not take into account that many
                juveniles in some lacustrine and estuarine habitats are captured at depths
                less than 1.83 m (6 ft) (Crance 1985).

                      Substrate. The suitability of substrate for juvenile riverine habitat is
                unclear. No SI curve was developed.

                      Cover.   Cover utilization by juveniles in riverine habitat is unclear.
                Therefore, no SI curve was developed.

                      Temperature.   The temperature SI curve for juveniles in riverine habitat
                was based on the temperature SI curve developed as component V, of the
                lacustrine HSI model.

                      Adults.   The SI curves for striped bass adults (Fig. 7) are for IFIM
                analyses Tf riverine habitat where nonspawning adults are found.           Only depth
                and temperature SI curves are available.        SI curves for velocity, substrate,
                and cover will need to be developed for a complete IFIM analysis of nonspawning
                adult riverine habitat.

                      Velocity.   Insufficient information was available to develop a velocity
                SI curve for adult striped bass.

                      Depth.  The depth SI curve for adults was based on the assumptions that:
                (1) a minimum depth of 0.45 m (1.5 ft) is required for unimpeded movement by
                adults; and (2) depths of 1.83 to 9.1 m (6 to 30 ft) are optimum.

                      Substrate.   Insufficient information was available to develop a substrate
                SI curve for adult striped bass.

                      Cover.   Insufficient information was available to develop a cover SI
                curve for adult striped bass.

                      Temperature.   The temperature SI curve for adults was based on the tem-
                perature SI curve (V,) developed as a component of the lacustrine HSI model.

                                                           43

                                                                             A velocity SI curve for
                                                                             adult striped bass is
                                                                             not available. Informa-
                                                                             tion on the relationship
                                                                             of the.variable to
                                                                             adult habitat suit-
                                                                             ability was insufficient
                                                                             to develop a curve.

                           Coordinates                                   1.0-

                                                                    x
                        x               y                                0.8-
                       (ft)            (SO
                                                                    >,   0.6-
                        0.0            0.0
                        1.4            0.0
                        6.0            1.0                               0.4
                       30.0            1.0
                      100.0            0.0
                                                                         0.2 -

                                                                         0.0
                                                                             0    6    12   18    @4   30

                                                                                      Depth (ft)

                                                                             A substrate SI curve for
                                                                             adult striped bass is
                                                                             not available. Informa-
                                                                             tion on the relationship
                                                                             of the variable to
                                                                             adult habitat suit-
                                                                             ability was insufficient
                                                                             to develop a curve.

                        Figure 7. SI curves for IFIM analyses of striped bass riverine
                        habitat for adults.

                                                           44

                                                                          A cover SI curve for
                                                                          adult striped bass
                                                                          is not available. Infor-
                                                                          mation on the relation-
                                                                          ship of the variable to
                                                                          adult habitat suit-
                                                                          ability was insufficient
                                                                          to develop a curve.

                                                                    1.0
                      Coordinates

                                                                x   0.8-
                     x               y
                   (OF)             (SO
                                                                    0.6-
                     0.0            0.0
                   53.6             0.0
                   64.4             1.0                             0.4-
                   75.0             1.0
                   86.0             0.0                             0.2-
                   100.0            0.0

                                                                    0.0
                                                                        35     50    65     80    95
                                                                                             0
                                                                              Temperature     F)

                                           Figure 7. (concluded).

                                                       45

                    REFERENCES

                    Albrecht, A. G.      1964.  Some observations on factors associated with survival
                      of striped bass eggs and larvae. Calif. Fish Game 50:(2)100-113.

                    American Public Health Association.        1981.   Standard methods for the examina-
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                                                                  48

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                                                             49

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                                                             51

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                Morgan,    R. P., II,   V. J.   Rasin, Jr.,    and   L. A.   Noe.    1973.    Effects of
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                                   1983. Sediment effects on eggs and larvae of striped bass and
                   white perch. Trans. Am. Fish. Soc. 112:220-224.

                Morgan, R. P., II, R. E. Ulanowicz, V. J. Rasin, Jr., Linda A. Noe, and G. B.
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                Morri s, D. J. , and B. J. Fol 1 i s.    1978.    Effects of striped bass predation
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                                                             55

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                                                                 56

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                                                             57

                     Scruggs, G. D. , Jr. , and J. C. Ful I er, Jr.      1955.   Indications of a freshwater
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                                                                   58

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                                                             59

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                                                                  60

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                                                      T

                                                            61

                 50272 -ioi
                 REPORT DOCUMENTATION          1. REPORT NO                              2.                     3. Recipient's Accession No.
                           PAGE                    FWS/OBS-82/10.85

                 4. Title and Subtitle
                    Habitat Suitability Index Models and Instream Flow Suitabilit                               5- Report Date
                    Curves:     Inland Stocks of Striped Bass.                                          Y       6. AUqUSt 1984

                 7. Author(s)
                    Johnie H. Crance                                                                            8. Performing Organization Rept. No.
                 9. Performing Organization Name and Address I nstream Fl ow and Aquati c Systems GrOL PO. Project/Task/Work Unit No.
                                                         Western Energy and Land Use Team
                                                         U.S. Fish and Wildlife Service                         11. Contract(C) or Grant(G) No.
                                                         Drake Creekside Building One                           (C:
                                                         2627 Redwing Road                                      (G
                                                         Ft. Collins, CO 80526-2899
                 12. Sponsoring Organization Name and Address Western Energy and Land Use Team                  13. Type of Report & Period Covered
                                                         Division of Biological Services
                                                         Research and Development
                                                         Fish and Wildlife Service                              14.
                                                         U.S. Department of the Interior
                 15. Supplementary Notes                 Washington, DC        20240

                 I& Abstract (Limit: 200 words)

                    The Habitat Suitability Index (HSI) models and instream flow Suitability Index (SI)
                    curves presented in this publication aid in identifying important variables that
                    determine the quality of striped bass habitat. Facts, concepts, and opinions
                    obtained from published and unpublished reports, a Delphi panel of 18 striped bass
                    experts/authorities, and the Striped Bass Committee, Southern Division, American
                    Fisheries Society, are synthesized and Presented-in a format that can be used for
                    habitat impact assessment and development of management alternatives.

                 17. Document Analysis a. Descriptors

                    Fishes
                    Habi tabi 1 i ty
                    Mathematical models

                    b. Identifiers/Open-Ended Terms
                    Striped bass
                    Morone saxatilis Walbaum
                    Habitat suitability
                    Instream Flow Incremental Methodology

                    c. COSATI Fieid/Group

                 I& Availability Statement                                                19. Security Class (This Report)  -11. No. of Pages
                    Release unlimited                                                          Unclassified                      61 pp
                                                                                          20. Securit Class (This Page)     22. Price
                                                                                               Uncyassified
                 (See ANSI-Z39.18)                                   See Instructions on Reverse                          OPTIONAL FORM 272 (4-77)
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                    U.S. GOVERNMENT PRINTING OFFICE: 1988-574-484/85,075 REGION NO. 8                                      Department of Commerce

                                                                                              61
                                                                                                                                                                          X       A10
                                                                                                                                      T

                       Hawaiian Islands, P                                                                              ---

                           Headquarters, Division of Biological
                             Services, Washington. DC                                                                                                                      P.!rl. Ri@. and
                       X   Eastern Energy and Landd Use Team
                             Leetown, WV                                                                                                L                                    Virgin Islands
                           National Coastal Ecosystems Town
                             Slidell, LA

                           Western Energy and Land Use Team
                             Ft. Collins, CO                                                                                                                            43

                           Locations of Regional Offices

                       REGION I                                                              REGION 2                                                  REGION 3
                       Regional Director                                                     Regional Director                                         Regional Director
                       U.S. Fish and Wildlife Service                                        U.S. Fish and Wildlife Service                            U.S. Fish and Wildlife Service
                       Lloyd Five Hundred Building, Suite 1692                               P.O. Box 1306                                             Federal Building, Fort Snelling
                       500 N.E. Multnomah Street                                             Albuquerque, New Mexico 87103                             Twin Cities, Minnesota 5 5 111
                       Portland, Oregon 97232

                       REGION 4                                                              REGION 5                                                  REGION 6
                       Regional Director                                                     Regional Director                                         Regional Director
                       U.S. Fish and Wildlife Service                                        U.S. Fish and Wildlife Service                            U.S. Fish and Wildlife Service
                       Richard B. Russell Building                                           One Gateway Center                                        P.O. Box 25486
                       75 Spring Street, S.W.                                                Newton Corner, Massachusetts 02158                        Denver Federal Center
                       Atlanta, Georgia 30303                                                                                                          Denver, Colorado 80225

                                                                                             REGION 7
                                                                                             Regional Director
                                                                                             U.S. Fish and Wildlife Service
                                                                                             10 11 E. Tudor Road
        qW                                                                                   Anchorage, Alaska 99503

                                                  T

                                                                                                                            SEWVICF
                                                                                             T           TERIOR
                                                                   U.S. FISH AND WILKIFE SERVICE

                                            As the Nation's principal conservation agency, the Department of the Interior has respon-
                                          sibility for most of our.nationally owned public lands and natural resources. This includes
                                          fostering the wisest use of our land and water resources, protecting our fish and wildlife,
                                          preserving the, environmental and cultural values of our national parks and historical places,
                                          and providing for the enjoyment of life through outdoor recreation. The Department as-
                                          S05ses our energy and mineral resources and works to assure that their development is in
                                          the best interests of all our people. The Department also has a major responsibility for
                                          American Indian reservation communities and for people who live in island territories under
                                          U.S. administration.

                                                                                                                   3 6668 14101 3054