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FWS/OBS-82/1 0.60JANUARY 1984

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HABITAT SUITABILITY INFORMATION:RAINBOW TROUT

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FWS/OBS-82/10.60January 1984

HABITAT SUITABILITY INFORMATION: RAINBOW TROUT

by

Robert F. RaleighP.O. Box 625

Council, 10 83612Terry Hickman

Endangered Species OfficeU.S. Fish and Wildlife Service

1311 Federal Building125 S. State Street

Salt Lake City, UT 84138

R. Charles SolomonHabitat Evaluation P r o c e G ~ r e sGroupWestern Energy and Land Use TeamU.S. Fish and Wildlife ServiceDrake Creekside Building One

2627 Redwing RoadFort Collins, CO 80526-2899

and

Patrick C. NelsonInstream Flow and Aquatic Systems Group

Western Energy and Land Use TeamU.S. Fish and Wildlife Service

Drake Creekside Building One2627 Redwing RoadFort Collins, CO 80526-2899

Western Energy and Land Use TeamDivision of Biological Services

Research and DevelopmentFish and Wildlife Service

U.S. Department of the InteriorWashington, DC 20240


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This report should be cited as:

Raleigh, R. F., T. Hickman, R. C. Solomon, and P. C. Nelson. 1984. Habitatsu i t ab i l i t y information: Rainbow t rout . U.S. Fish Wildl. ServoFWS/OBS-82/10.60. 64 pp.


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PREFACE

The Habitat Suitabil i ty Index (HSI) models presented in this publicationaid in identifying important h ab it at va ria ble s. Facts, ideas, and conceptsobtained from th e research l i t e ra ture and expert reviews are synthesized andpresented in a format that can be used fo r impact assessment. The models ar ehypotheses of species-habi ta t re la t ionships , and model users should recognizethat th e degree of veracity of th e HSI model, SI graphs, and assumptions willvary according to geographical area and the extent of the data base forindividual variables. After clear study objectives have been set , th e HSImodel bui ld ing t echn iques p re sent ed in U.S: Fish and Wildlife Service (1981)1and th e general guidelines for modifying HSI models and estimating modelvariables presented in Ter-re l l et a l. (1982)2 may be useful for simplifyingand applying th e models to specific impact assessment problems. Simplifiedmodels should be tested with independent data sets i f possible.

A brief discussion of the appropr ia teness of using selected Suitabil i tyIndex (SI) curves from HSI models as a component of th e Instream FlowIncremental Methodology (IFIM) is provided. Additional SI curves, developedspecifically fo r analysis of rainbow t rout habitat with IFIM, also ar epresented.

The U. S. Fi sh and Wi 1dl i fe Servi ce encourages mode 1 users tocomments, suggestions, and t e s t results that may help us i ncr ea se theand effectiveness of this habitat-based approach to impact assessment.send comments to:

Habitat Evaluation Procedures Group orInstream Flow and Aquatic Systems GroupWestern Energy and Land Use TeamU.S. Fish and Wildlife Service2627 Redwing RoadFt. Collins, CO 80526-2899

provideut i l i tyPlease

1U.S. Fish and Wildlife Service.habitat su i tab i l i ty index models.Ecol. Servo n.p.

1981. Standards for th e development of103 ESM. U.S. Fish Wildl. Serv., Div.

2Terrell, J . W., T. E. McMahon, P. D. Inskip, R. F. Raleigh,Williamson. 1982. Habitat su i tab i l i ty index models: Appendix A.fo r riverine and lacustrine applications of fish HSI models withEvaluation Procedures. U.S. Fish Wildl. Servo FWS/OBS-82/10.A. 54

i i i

and K. L.Guidelines

the Habita tpp.


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CONTENTS

Page

PREFACE i i iFIGURES viTABLES vi iACKNOWLEDGMENTS vi i i

HABITAT USE INFORMATION 1

Genera 1 1Age, Growth, and Food 1Reproduct ion 2Anadromy 3Specific Habitat Requ i r emen t s . . . . . . . . . . 4

HABITAT SUITABILITY INDEX (HSI) MODELS..... 9Model A p p l i c a b i l i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Mode 1 Descri pt ion 11Sui tab i l i ty Index (SI) Graphs for Model Variables 13Riverine Model 23Lacustrine M o d e l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Interpreting Model O u t p u t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

ADDITIONAL HABITAT MODELS 33Mode 1 1 33Model 2 36Model 3 36Model 4 36

INSTREAM FLOW INCREMENTAL METHODOLOGY (IFIM) . . 37Sui tab i l i ty Index Graphs as Used in IFIM 37Availabil i ty of Graphs for Use in IFIM 39

REFERENCES 54

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Number

1

2

3

4

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FIGURES

Diagram i l lus t ra t ing the relationship among modelvariables, components, and HS1 . .

SI curves for rainbow t rout spawning velocity, depth,substrate, and temperature .

SI curves for rainbow trout fry velocity,depth,

substrate,and temperature .

SI curves for rainbow trout juvenile velocity, depth,substrate, and temperature .

$1 curves for rainbow trout adu lt v el oc it y, depth,substrate, and temperature .

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Number

1

2

3

4

5

6

TABLES

Matrix table for d ispl ay ing su i tab i l i ty indices (S1l s) forrainbow trout habitat variables .

Literature sources and assumptions for rainbow trout sui t -abi l i ty indices .

Sample data sets using th e nonanadromous riverine rainbowtrout HS1 model .

Average va 1.ue method .

Average value, probabili ty method .

Ava i l abil i ty of curves fo r I FIM ana ly s is of rainbow trouthabi t a t .

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ACKNOWLEDGMENTS

Robert Behnke, Colorado State University; Leo Lentsch, U.S. Fish andWildlife Service; and Tom Weshe, University of Wyoming, provided comprehensivereviews and many helpful comments and suggestions for improving the manuscriptand the model. The Oregon Cooperative Fishery Research Unit conducted th el i terature review for the report. Cathy Short and Tric1a Rosenthal conductededitorial reviews, and word processing was provided by Carolyn Gulzow and DoraIbarra. The cover i l lust ra t ion was prepared.by Jennifer Shoemaker.

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RAINBOW TROUT (Salmo ga i rdneri )

HABITAT USE INFORMATION

Genera1

Because of variat ions in the i r l i f e history pat tern and th e habi tat inwhich they spend the majority of the i r adul t l ives , rainbow t rou t (Salmogairdneri) can be subdivided in to three bas ic e co logica l forms: (1) anadromoussteel head t rou t ; (2) resident stream rainbow t rout ; and (3) lake or reservoirdwelling rainbow t rout . I t i s important to recognize that there i s a geneticor hereditary basis for each ecological form. For example, a "Lake orreservoi r" rainbow may react very di f fe ren t ly to envi ronmenta1 s t imul iassociated with survival , feeding, and growth i f i t belongs to a populationthat has been evolving and adapting to the par t icu la r lake for hundreds orthousands of years , when compared to hatchery rainbow t rout tha t have j u s tbeen released in the lake.

Nonanadromous rainbow t rout are native to the Pacific Coast drainagesinland as far,as the Rockies and from th e Rio de l Presidio River in Mexico tothe Kuskokwim River in Sou thwestern Alaska (Behnke 1979). They are alsonative to the Peace River drainage of Brit ish Columbia and the headwaters ofthe Athabaska River (of the McKenzie River basin) in A"lberta (MacCrimmon1971). Their p re se nt range extends from the Arctic Circle to 55 0 S l a t i tude .They are perhaps the most widely introduced f ish species; the only cont inentlacking rainbow t rout i s Antarctica (McAfee 1966; MacCrimmon 1971). Rainbowt rout occur from 0 to 4,500 mabove sea level (MacCrimmon 1971).

Anadromous s teel head t rout are di s t r i buted along th e Pacif i c coast fromthe Santa Ynez Mountains, California, to the Alaska Peni ns ul a (J ord an andEvermann 1902; Withler 1966). Large rainbow t rout on and north of the AlaskaPeninsula appear to be nonanadromous.

Age, Growth, and Food

Female rainbow t rout typ ica l ly become sexually mature during the i r th i rdyear; males become sexually mature during the i r second or th i rd year (Holton1953; Lag1er 1956; McAfee 1966). Life expectancy averages 3 to 5 years inmost southern lake populations, but l i f e expectancy of s teel head and northernlake populations appears to be 4 to 8 years . Maximum size also varies withpopulation, area, and habi ta t . Steelhead may grow to 122 cm long and weigh16 kg. The average angl er I s catch i s 3.6 to 4 kg. Great Lakes rainbow growto 244 cm, but seldom exceed 9 kg (Scot t and Crossman 1973). Size in wild

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s tage . Juven i l e s migrate from natal streams to a f reshwater lake rear ingar-ea , ins tead of to the ocean. Lake rainbow t r ou t most commonly spend twosummers in a st ream and two summers in a lak e b efo re maturing (Greeley 1933).Spawning takes place dur ing the growing season in an i n l e t or an o u t l e t stream,with more than 90% of the t r o u t r e tu rn ing to the st ream of nata l or ig in

(Greeley 1933; Lindsey e t a l . 1959). Lakes with no i n l e t or ou t l e t streamsgenera l ly do not possess a reproducing population of rainbow t r o u t . Whetherspawning adu l ts en te r through an i n l e t or an o u t l e t , they and t h e i r progenywi 11 re turn to the 1ake (Lindsey e t a 1. 1959). These movements from nata ls i t e s t o lake r ea r ing areas appear to be d i rec ted by genet ic /environmenta li n t e r a c t i ons (Raleigh 1971).

Spawning usual ly begins one month e a r l i e r in the o u t l e t than in the i n l e t(Lindsey e t a l . 1959; Hartman e t a l . 1962); the d i ffe rence in t ime i sapparent ly r e la ted to temperature d i ffe rences (Lindsey e t a l . 1959). InBothwell Creek, a t r i bu t a ry of Lake Huron, 65% of the spawning run were r epea tspawners (Dodge and MacCrimmon 1970). The t yp ica l surv ival ra te of r epea tspawners i s 10-30%, with extremes from 1% to more than 65%.

Average fecundity of rainbow t r o u t i s r e la ted to length , but i s highlyvar iab le , ranging from 500 to 3,161 eggs per st ream res iden t female (Carlander1969). Fecundity of lake r e s i d en t females ranges from 935 to 4,578 eggs perfemale, with an average of 2,028 eggs per female (Mann 1969).

Anadromy

Anadromous s tee 1head spawn in f reshwater streams. Stee 1head smo l t an dmigrate in l a t e spr ing (Wagner 1968; Chrisp and Bjornn 1978). Photoperiod

appears t o be the dominant t r igger ing mechanism fo r p a rr -smo lt t ra n sf o rma t io n ,with temperature affec t ing the r a te of transformation (Wagner 1974). Smoltst h a t have not migrated by approximately the summer s o l s t i c e r eve r t to par r andattempt t o migrate the fo l lowing season (Zaugg and Wagner 1973). Juveni le sreside in f reshwater fo r 1 to 4 year s b ef or e m ig ra tin g to the sea as smolts .They mature a f t e r 1 to 4 year s of ocean res idence an d re tu rn to f reshwaterr i ve r s to spawn (Chapman 1958; Withler 1966). A la rge number of the s tee l headadu l ts d ie a f t e r spawning, but some (3 to 53%) re turn to the ocean and spawnagain (Bjornn 1960; Withler 1966; F ult on 1970). Steel head spawners tend to bel a rg e r and o lde r in the northern por tion o f t h e i r range (With ler 1966).

There are both win te r and summer-run s t ee l head. Summer-run adu l t s en t e rf reshwater r i ve r s in the spr ing and ear ly summer. Winter-run s tee l head en t e rf reshwater r i ve r s in the f a l l and winte r. As many as 98.8% of the t r o u tre turn to t h e i r nata l st ream (McAfee 1966). Both groups t yp i c a l l y spawn inthe spr ing and ea r l y summer months, March through ea r ly Ju ly (With ler 1966;Orcutt e t a l . 1968), al though spawning a t othe r t imes of the yea r has beenr epo r ted . Summer-run and winter- run s tee l head are d i s t ingu i shed by d i ffe rencesin behavior p r io r to spawning and, to a l imi t ed ex ten t , by appearance (With ler1966).

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When f ish migrate from freshwater to sa l twa te r, they are moving from ahypotonic medium to a hypertonic medium. Gi l l Na-K ATPase ac t i v i t y appears tobe r e la ted to s al tw a te r t ol er an ce and smolting (Conte and Wagner 1965; Zauggand Wagner 1973; Adams e t a l . 1975). Water temperature a f f ec t s Na-K-relatedATPase ac t i v i t y. J uv en il e s te el he ad kept in water warmer than 13 C fromMarch to June experienced reduced l eve l s of smol t i f ica t ion and very low levelsof ATPase ac t i v i t y (Zaugg and McLain 1972; Zaugg and Wagner 1973; Wagner1974). Water temperatures of 10.5 to 13 C resul ted i n a moderate ATPaseresponse, and temp er atu re s o f 6.5 to 10 C resul ted in the highest ac t i v i t yl eve ls fo r the longest period of time (Adams e t a l . 1975). The e f f e c t oftemperature on ATPase ac t iv i ty i s reversible within a season (Zaugg and McLain1972) .

Coeff ic ien t of condi t ion i s another ind ica tor of. parr-smolt t ransformat i on . J uv en il e s te el he ad not undergoing a smolt t ransformat ion do not losewei ght ; whereas, s tee l head undergoi ng t ransformat i on lose enough wei ght toresul t i n a grea t ly reduced coeff i ci en t of condi t i on (Adams e t a 1. 1973;

Wagner 1974).

A fork length ( i . e . , an t e r i o r most extremity to the notch in the t a i l finof fo rk - t a i l ed f i sh or to the cen te r of the t a i l f in when the t a i l i s notforked) of 160 mm i s the average length ju ve nile p arr must reach before theyundergo th e p hy si olo gic al and morphological changes of smolting (Fess le r andWagner 1969; Chri sp and Bjornn 1978). Hatchery-reared s tee 1head typi ca l lyreach c r i t i c a l size in one growing season, but nat ive stream s te el he ad u su al lyrequire two or more growing seasons (Chrisp and Bjornn 1978). Migratingsmolts a t the lower end of the minimum length requirement stay in the oceanlonger than smolts t h a t are l a rge r in size when they migrate (Chapman 1958).

The freshwater hab i t a t requirements of adu l t and juven i le stee l head areassumed to be es sen t i a l l y the same as those fo r o ther rainbow t rou t . Except ions fo r stee lhead are : (1) low temperature 13 C) requirements duringthe spring months for smol t i f ica t ion of juven i le s ; and (2 ) the presence ofmoderate temperatures (preferably s 20 C) and f r e she ts (periodic high flow s)during the upstream migration of adu l t s .

Specif ic Habi ta t Requirements

Optimal rainbow t rou t r iv er in e h ab ita t i s character ized by c l ea r, coldwater; a s i l t - f r e e rocky subs t ra te in r i f f l e - run areas ; an a pp ro ximat el y 1:1

p o ol -t o- ri ff le r at io , with areas of slow, deep water ; wel l -vegeta ted streambanks; abundant i ns tr eam cov er ; and re la t ively s tab le water flow, temperatureregimes, and stream banks (Raleigh and Duff 1980).

Optimal la cu str in e h ab ita t i s character ized by c l ea r, cold, deep lakest ha t are t yp ica l ly o l igo t roph ic , but may vary in s ize and chemical qua l i ty,par t i cu l a r l y in r e se rvo i r hab i t a t s . Rainbow t rou t are primari ly streamspawners and general ly requi re t r i butary streams wi th gravel subs t ra te inr i f f l e areas fo r reproduction to occur.

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Trout product ion is t yp ic al ly g re at es t in streams with a pool- to-r iff lerat io of approximately 1: 1 (Fortune and Thompson 1969; Thompson and Fortune1970). Pools are inhabited throughout th e year by adult and juvenile streamrainbow t rout . Pools are important to t rout as a refuge from adverse conditions during th e winter. Because pools differ in the ir ab i l i ty to provideresting areas and cover, this model subdivides pools into three classes .Lewis (1969) found that streams with deep, low velocity pools containingextensive cover had th e most stable t rout populations.

Available t rout l i te ra ture does not often clearly distinguish betweenfeedi ng stat ions, escape cover, and wi nter cover requi rements. Primerequisites fo r optimal feeding stations appear to be low water velocity andaccess to a p1ent iful food supply; i . e . , energy accretion at a low energycost. Water depth is not clearly defined as a selection factor, and overheadcover is preferred but not essential . Escape cover, however, must be nearby.The feeding stations of dominant adult t rout include overhead cover whenavailable.

The feeding stations of subdominantadults

andjuveniles,

however,do not always include overhead cover. Antagonistic behavior occurs at feedingstations and hierarchies are established, but escape cover is often shared.

Cover is recognized as one of th e essential components of t rout streams.Boussu (1954) was able to increase th e number and weight of t rout in streamsections by adding a r t i f i c i a l brush cover and to decrease numbers and weightof t rout by removi ng brush cover and undercut banks. Lewi s (1969) reportedthat th e amount of cover was important in determining th e number of t rout insections of a Montana stream. Stewart (1970) found that mean depth and under-water, overhanging bank cover were the most important variables in determiningth e density of brook and ra t nbow t rout longer than 18 cm in a northcentralColorado stream. Cover for adult t rout consists of areas of obscured streambottom in water ~ 15 cm deep with a velocity of s 15 cm/sec (Wesche 1980).Wesche (1980) reported that , in larger streams, th e abundance of t rout ~ 15 cmin len gth in cr eas ed with water depth; most t rout were at depths of at least15 em. Cover is provided by overhanging vegetation; submerged vegetation;undercut banks; instream objects, such as debris piles, logs, and large rocks;pool depth; and surface turbulence (Giger 1973). A cover area of ~ 25% of th etotal stream area provides adequate cover for adult t rout; a cover area of~ 15% is adequate fo r juveniles. The main uses of summer cover are probablypredator avoidance and resting.

In some streams, th e major factor l imiting salmonid densi t ies may be th eamount of adequate overwi nteri ng habi t a t , rather than th e amount of summerrearing habitat (Bustard and Narver 1975a). Winter hiding behavior insalmonids is tr iggered by low temperatures (Chapman and Bjornn 1969; Everest1969; Bustard and Narver 1975a,b). Cutthroat t rout were found under boulders,log jams, upturned roots, and debris when temperatures neared 4 to 8 C,depending on the water velocity (Bustard and Narver 1975a). Everest (1969)found juvenile rainbow t rout 15 to 30 cm deep in th e substrate, which wasoften covered by 5 to 10 cm of anchor ice. Lewis (1969) reported tha t , duringwi nter, adult ra i nbow trout tended to move into deeper water ( f i r s t cl as spools). Bjornn (1971) indicated that downstream movement during or precedingwinter did not occur i f suff icient winter cover was available locally. Trout

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move to winter cover to avoid physical damage from ic e scouring (Hartman 1965;Chapman and Bjornn 1969) and to conserve energy (Chapman and Bjornn 1969;Everest 1969).

Headwater t rout streams are relat ively unproduct ive . Most energy inputsto th e stream ar e in th e form of allochthonous materials, such as terrestr ia lvegetation and terrestr ia l insects (Idyll 1942; Chapman 1966; Hunt 1971).Aquatic invertebrates are most abundant and diverse in r i ff le areas withrubble substrate and on submerged aquatic vegetation (Hynes 1970). However,optimal substrate fo r maintenance of a diverse invertebrate population consistsof a mosaic of mud, gravel, rubble, and boulders, with rubble dominant. Apool - to - ri f fl e r a ti o of about 1:1 (approximately a 40 to 60% pool area) appearsto provide an optimal mix of food producing and rearing areas for t rout(Needham 1940). In r i ff l e areas, th e presence of fi nes (> 10%) reduces th eproduct ion of invertebrate fauna (based on Cordone and Kelly 1961; Crouse e ta l . 1981).

Canopy cover is important in maintaining shade for stream temperaturecontrol and in providing allochthonous materials to th e stream. Too muchshade, however, can res t r ic t primary productivity in a stream. Stream temper-atures can be increased or decreased by controlling th e amount of shade.About 50 to 75% midday shade appears optimal for most small t rout streams(adapted from Oregon/Washington Interagency Wildlife Conference 1979). Shadingbecomes less important as stream gradient and size increase. In addition, awell vegetated riparian area helps control watershed erosion. In most cases,a buffer s t r ip about 30 m wide, 80% of which is ei ther well vegetated or hasstab 1e rocky stream banks, provi des adequate erosi on control and ma i ntainsundercut stream banks character ist ic of good t rout habitat. The presence offines in r i ff le- run areas can adversely affect embryo survival, food produc-t ion, and cover for juveniles.

There is a defini te relationship between th e annual flow regime and th equality of t rout habitat. The most cri t ical period is typically during baseflow (lowest flows of la te summer to winter). A base flow ~ 50% of th e averageannual daily flow is considered excellent for maintaining quality t routhabitat, a base flow of 25 to 50% is considered fa i r, and a base flow of < 25%is considered poor (adapted from Binns and Eiserman 1979; Wesche 1980).

Adult. Dissolved oxygen requirements vary with species, age, prioracclimation temperature, water velocity, activi ty level, and concentration of

substances in th e water (McKee and Wolf 1963). As temperature increases, th edissolved oxygen saturation level in th e water decreases, while th e dissolvedoxygen requi rement fo r the fi sh increases. As a resul t , an increase intemperature resulting in a decrease in dissolved oxygen can be detrimental toth e fish. Optimal oxygen levels fo r rainbow t rout are not well documented,but appear to be ~ 7 mg/l at temperatures ~ 150 C and ~ 9 mg/l at temperatures> 150 C. Doudoroff and Shumway (1970) demonstrated that swimming speed andgrowth rates fo r salmonids declined with decreasing dissolved oxygen levels.In th e summer ( ~ 100 C), cutthroat t rout generally avoid water with dissolvedoxygen levels of less than 5 mg/l (Trojnar 1972; Sekulich 1974).

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The inc ip ien t l e tha l level o f disso lved oxygen fo r adu l t and j uven i l erainbow t r o u t i s approximately 3 mg/l or l e s s , depending on environmentalcondi t ions , espec ia l ly temperature (Gutse l l 1929; Burdick e t a l . 1954;Alabaster e t a l . 1957; Downing and Merken 1957; Doudoroff and Warren 1962).Although f i sh can survive a t concen t r a t ions j u s t above t h i s l ev e l , they must

make v ar io us p hy si ol og ic al a da pta tio ns to low l eve l s o f d is so lv ed oxygen t h a tmay jeopard ize t h e i r heal th (Randall and Smith 1967; Kutty 1968; Hughes andSaunders 1970; Cameron 1971; Holeton 1971). Fo r example, low l eve l s ofdisso lved oxygen can r e su l t in reduced fecundi ty and even prevent spawning.Large f luc tua t ions in disso lved oxygen may cause a reduction in food consump-t i on and impaired growth (Doudoroff and Shumway 1970).

The upper and lower i nc i pi en t 1etha 1 temperatures fo r adu l t ra i nbow are25 and 0 C, re spec t ive ly (Black 1953; Lagler 1956; McAfee 1966; Bidgood andBers t 1969; Hokanson e t a 1. 1977). Zero growth r a te occurred a t 23 C fo rrainbow t r ou t in the l abo ra to ry (Hokanson e t a l . 1977). Changes in the natura lgrowth r a te of rainbow t r ou t are detr imental to t h e i r development and su rv iva l .Therefore , 25 C should 'be cons idered the upper l im i t su i t ab le fo r rainbowt r ou t and then only for shor t periods of t ime. Adult lake rainbow t r o u ts e l e c t wate rs with temp erature s between 7 to 18 C (Fas t 1973; May 1973) andavoid permanent res idence where tempera tures are above 18 C (May 1973).Adult stream rainbow t r o u t se l e c t temperatures between 12.0 and 19.3 C(Garside and Tai t 1958; Bell 1973; Cherry e t a l . 1977; McCauley e t a l . 1977).Dickson and Kramer (1971) reported t h a t the g r e a t e s t scope of rainbow t r ou ta c t i v i t y occurred a t 15 and 20 C when t e s t ed a t 5 C temperature i n t e r va l s .S tre am ra in bow t r o u t se l e c t temperatures between 12 and 19 C; lake r e s i d en tt r ou t avoid t empe ra tu re s> 18 C. Therefore , the optimal temperature rangefo r rainbow t r o u t i s assumed to be 12 to 18 C.

The depth d i s t r i bu t ion of adu l t lake rainbow t r o u t i s usual ly a funct ionof disso lved oxygen, tempera ture , and food. Adult lake rainbow t r o u t remaina t depths s the 18 C isotherm and a t d i s so 1ved oxygen 1 ev e 1s > 3 mg/l (May1973; Hess 1974).

Focal poin t ve loc i t i e s fo r adu l t cu t t h ro a t t r o u t a t t e r r i t o r i a l s t a t i onsin Idaho streams were primari ly between 10 and 14 em/sec, with a maximum of22 em/sec (G r i f f i t h 1972). The focal po in t ve loc i t i e s fo r adu l t rainbow t r o u tare assumed t o be s imi la r.

Precise pH to lerance and optimal ranges are not well documented fo rrainbow t r ou t . Most t r ou t populat ions can probably t o l e r a t e a pH range of 5.5to 9.0, with an optimal range of 6.5 to 8.0 (Hartman an d Gil l 1968; Behnke andZarn 1976).

Withler (1966) suggested t h a t the co r r e l a t i on between the w in ter s t ee l headrun and increased water volume ind ica tes t h a t a f r e she t condit ion i s requiredto i n i t i a t e upstream movement of spawners. Everes t (1973) s ta ted t h a t speedof migration of summer-run s tee l head in the Rogue River was i nve rse ly r e la tedto temperature and di r e c t ly r e la ted to streamfl ows. Hanel (1971) observedt h a t s teelhead migration i n to the Iron Gate f ish hatchery ceased when thewater temperature dropped to 4 C and did not resume fo r severa l weeks un t i l

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more than 1 m from cover. As the young t rout grow, they move to deeper,faster water. Everest (1969) suggested that one reason for th is movement wasth e need for cover, which is provided by increased water d ep th, s urf ace turbulence, and substrate that consists of large material.

Stream resident t rout fry usually overwinter in shallow areas of lowvelocity near th e stream margin, with rubble being the principal cover (Bustardand Narver 1975a). Optimal size of substrate used as winter cover by rainbowfry and small juveniles ranges - from 10 to 40 cm in diameter (Hartman 1965;Everest 1969). An area of substrate of th is size class that is ~ 10% of th etotal habitat probably provides adequate cover fo r rainbow fry and smalljuveniles. The use of small diameter rocks (gravel) for winter cover mayresul t in increased mortality due to greater shif t ing of th e substrate (Bustardand Narver 1975a). The presence of fi nes ( ~ 1 0 % )in th e r i ff l e-run areasreduces the value of th e area as cover for fry and small juveniles. Mantelman(1958) reported a preferred temperature range of 13 to 19 C fo r fry. Becausefry occupy habitats cont iguous with adults , thei r temperature and oxygenrequirements are assumed to be similar to those of adults.

Juvenile. Griffi th (1972) reported focal point veloci t ies fo r juvenilecutthroat in Idaho of between 10 and 12 cm/sec, with a maximum velocity of22 cm/sec. Metabolic rates are h igh est between 11 and 21 C, with an apparentoptimal temperature of between 15 and 20 C (Dickson and Kramer 1971). Insteel head s tr eams, tempera tures should be < 13 but> 4 C (optimal 7 to 10 C)from March until June for normal smoltification to occur (Wagner 1974; Adamse t a l . 1975).

Common types of cover fo r juvenile t rout are upturned roots, logs, debris

piles, overhanging banks, r i ff l e s , and small boulders(Bustard

and Narver1975a). Young salmonids occupy different habitats in winter than in summer,with log jams and rubble important as winter cover. Wesche (1980) observedthat larger cutthroat t rout (> 15 cm lDng) and juveniles ( ~ 15 cm) tended touse instream substrate cover more often than they used streamside cover(undercut banks and overhanging vegetation). However, juvenile brown t routpreferred s tr eamside cover. An area of cover ~ 15% of th e total habitat areaappears to provide adequate cover fo r juvenile t rout .

Because juvenile rainbow t rout occupy habitats contiguous with adults,the ir temperature and oxygen requirements ar e assumed to be similar.

HABITAT SUITABILITY INDEX (HSI) MODELS

Figure 1 i l lustra tes the assumed relationships among model variables,components, and th e HSI for the rainbow t rout model.

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Habitat variables Model components

Ave. thalweg d ~ e P t hV.)% i nst ream cover (V 6A) - - - - - - - - - = : 3 ~Adult

~ 6 pools (VIC)

Pool c la ss r at in g (V , S )

% i nst ream cover (V 6J)

~pools ( V l O ) - - - - ~ - - - - - - - - - = = = - J U V e n i l ePool class rating (V , S )% s ub st ra te s iz e C l a s s ~ ( v . )

% pools (V , , )~

Fry

% r i ff le fines (V , 6B) HSI

Ave. max. temp. (V 2 )

Ave. min. D.O. (V 3 )

Ave. water velocity

Ave. gravel size inspawning areas (V,)

% r i ff le fines (V, 6A)

- - - - - - = = = : : : : : : : ~ ~Embryo

Max. tempera ture (V ,)

Ave. min. D.O. (V 3 )

- - - = = = = = = ~ ~Othera

Ave. base flow (V , . )pH (V , 3 ) -- - - - - - - - - - __

Predominant substrate

% streamside vegetation

% midday shade ( V, , ) b - - - - - - - - - - - - - - - - J

%Ave. daily flow (V, . ) c - - - - - - - - - - - - - - J

% r i ff le fines ( V , 6 B ) - - - - - - - - - ~

% streamside vegetation

aVariables that a ff ec t a ll l i fe stages.

bOptional variables.

CSteelhead variable.

Figure 1. Diagram i l lustrating the relationship among model variables,components, and HSI.

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Model Applicability

Geographic area. The following models are applicable over the entireNorth American range of the rainbow t rout .

Season. The model rates the year-round freshwater habitat of rainbow

t rout .

Cover types. The model is app li cable to freshwater riverine or lacustrinehabitats.

Minimum habitat area. Minimum habitat area is th e minimum area of contin-uous habi ta t that is requi red for a speci es to 1i ve and reproduce. Becauset rout can move considerable distances to spawn or locate suitable summer orwinter rearing habitat, no attempt has been made to define a minimum amount ofhabitat for the species.

Verification level. An accep tabl e l evel of performance fo r this rainbowt rout model is for i t to produce an index between 0 and 1 that the authors andother biologists familiar with rainbow t rout ecology believe is positivelycorrelated with long term carrying capacity of the habitat. Model verificat ionconsisted of testing the model outputs from sample data sets developed by theauthors to simulate rainbow t rout habitat of high, medium, and low quality andmodel review by rainbow t rout experts.

Model Description

The HSI model consists of five components: Adult (C A); Juvenile (CJ ) ;

Fry (C F); Embryo (CE); and Other (CO), Each l i fe stage component containsvariables specifical ly related to that component. The component Co contains

variables related to water quality and food supply th at affe ct all l i fe stagesof rainbow t rout .

The model uti l izes a modified limiting factor procedure. This procedureassumes that model variables and components with sui tabi l i ty indices in theaverage to good range, > 0.4 but < 1.0 , can be compensated for by hi ghersu i tab i l i ty indices of other related model variables and components. However,variables and components wi th su i tab i l i t ie s s 0.4 cannot be compensated forand, thus, become l imit ing fac to rs for the habitat su i tab i l i ty.

Adult component. Variable V6 , percent instream cover, is included because

s tanding crops of adult t rout are assumed to be related to the amount of coveravailable based on studies of brook and cutthroat t rout . Percent pools (V i O)i s included because pools provide cover and resting areas for adult t rout .Variable V l O also quantifies the amount of pool habitat that is needed.

Variable ViS' pool class rating, is included because pools differ in the

amount and quality of escape cover, winter cover, and resting areas that they

11


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provide. Average thalweg depth (V 4 ) i s included because average water depthaffects th e amount and quality of pools and instream cover available to adultt rout and the migratory access to spawning and rearing areas.

Juvenile component. Variables Vs , percent instream cover; V D , percent

pools; and ViS' pool class rating are included in the juvenile component forthe same reasons l isted above for th e adult component. Juvenile rainbow t routuse these essential stream f ea tu re s f or escape cover, winter cover, and restingareas.

Fry component. Variable Va, percent substrate size class, is includedbecause t rout fry util ize substrate as escape cover and winter cover. VariableVi O, p erc en t pool s, is included because fry use the shallow, slow water areasof pools and backwaters as resting and feeding stations. Variable V1 6 , percent

r i ff le fines, is i ncl uded 'b ecau se t he percent fines affects the abi l i ty of th efry to uti l ize the rubble substrate fo r cover.

Embryo component. I t i s assumed that habitat suitabil i ty for t routembryos depends primari l y on average maximum water temperature, V2 ; averageminimum dissolved oxygen, V 3 ; average water velocity, Vs ; gravel size inspawning areas, V7 ; and percent r i ff le f ines , ViS' Water velocity (V s ) ,

gravel size (V 7 ) , and percent fines (ViS) are interrelated factors th at e ffe ctthe transport of dissolved oxygen to the embryo and th e removal of metabol icwaste products from the embryo. In addition, the presence of too many fines

in the redds blocks movement of th e fry from th e incubati ng gravels to thestream.

Other component. This component contains model var ia bl es f or two subcom-ponents, water qual i ty and food supply, that affec t all 1i fe stages. Thesubcomponent water quality contains four variables: maximum temperature (Vi);

average minimum dissolved oxygen (V 3 ) ; pH (V 1 3 ) ; and average base flow (V 1 4 ) .

The waterflow of all streams fluctuates on a seasonal cycle, and a correlationexists between th e average annual daily streamflow and th e annual low baseflow period. Average base flow (V 1 4 ) i s inc luded to quanti fy the relationship

between annual water flow fluctuations and t rout habitat suitabil i ty. Thesefour variables affect the growth and survival of all l i fe stages exceptembryos, whose water quality requirements are included with the embryocomponent. The subcomponent food supply conta ins three va r i ab1 es : domi nantsubstrate type (V 9 ) ; percent streamside vegetation (V l l ) ; and percent r i ff lefines (ViS)' Predominant substrate type (V 9 ) is included because the abundanceof aquatic insects , an important food item for rainbow t rout, is correlatedwith substrate type. Variable V 16 , percent fines in r i ff le- run and spawningareas, is included because the presence of excessive fines in r i ff le- run areas

12


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reduces th e product ion of aquatic insects .

allochthonous materials ar e an importantproductive trout streams.

Variable V l l is included because

source of nutrients in cold, un-

Variables V1 2 , VI?' and V 1 8 are optional variables to be used only when

needed and appropriate. Streamside vegetation, V1 2 , is an important means ofcontrolling soil erosion, a major source of fines in streams, and fo r input ofterrestr ia l insects . Variable VI?' percent midday shade, is included becauseth e amount of shade can affect water temperature and photosynthesis in streams.Average daily flows, V 1 8 , are associated with rapid upstream migration ofsteel head adults. Variables V1 2 and VI? ar e used primarily for streams ~ 50 m

wide where temperature, photosynthesis, or erosion problems occur or whenchanges in th e riparian vegetation are part of a potential project plan.Variable V1 8 is used only for habitat evaluation fo r spawning migration of

steel head t rout .

Suitabil i ty Index (SI) Graphs for Model Variables

This sect ion conta ins suitabil i ty index graphs fo r th e 18 model variables.Equations and instructions fo r combining groups of variable SI scores intocomponent scores and component scores into rainbow t rout HSI scores areincluded.

The graphs were constructed by quantifying information on th e effect ofeach habitat variable on th e growth, survival, or biomass of rainbow t rout .The curves were bui l t on th e assumption that increments of growth, survival,or biomass plotted on the y-axis of th e graph could be direct ly converted intoan index of su i tab i l i ty from 0.0 to 1.0 for the species, with 0. 0 indicatingunsui tabl e condi ti ons and 1.0 indicating optimal conditions. Graph trend1 ines represent th e authors ' best estimate of suitabi 1 i ty for the variouslevels of each variable. The graphs have been reviewed by biologis ts familiarwith th e ecology of th e species, but some degree of SI var iabi l i ty exists.The user is encouraged to modify th e shape of th e graphs when existing regionalinformation indicates that th e variable su i tab i l i ty relationship is differentfrom that i l lus t ra ted .

The habitat measurements and the SI graph construction ar e based on th epremise that extreme, rather than average, values of a variable most often1 imit th e car ry ing capac it y of a habitat. Thus, extreme conditions, such asmaximum temperatures and minimum dissolved oxygen levels, are often used inth e graphs to derive th e SI values for th e model. The le t ters Rand L in th ehabitat column identify variables used to evaluate riverine (R) or lacustrine(L) habitats .

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24/76

R,L V3 Average mlnlmum 1.0dissolved oxygen(mg/1) during the

0. 8la te growing season > ,+J' r -

:;:::: 0.4..Cltt l+J' ; 0. 2( / )

0. 0a 25 50 75 100

em/sec

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R Percent instreamcover during thela te growing seasonlow water periodat depths ~ 15 cmand velocit ies< 15 cm/sec.

J = juvenilesA = adults

x 0.8OJ"'C

oS 0.6~;= 0.4. r -

.. 0to. ~ 0.2: J

VJ

o 10 20%

30 40

R Average size of substrate (cm) in spawning areas, preferablyduring the spawningperiod.

A = average size ofspawner < 50 cm

B = average size ofspawner ~ 50 cm

To derive an averagevalue for use with graphV7 , include areas con-

taining the best spawningsubstrate sampled untilall potential spawningsi tes ar e included oruntil the sample containsan area equal to 5% of thetotal rainbow habitatbeing evaluated.

16

1. 0

x 0.8OJ"'CC......

> , 0.6+J. r -

:;: 0.4.. 0to+J. r -

0.2JVJ

0.00 5

em

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R Percent substrate sizeclass (10 to 40 cm)used fo r winter andescape cover by fryand small juveniles.

x 0.8(]J- 0C~ 0 .6> ,+J

:;:::: 0.4. 0co

~ 0.2:::JV' l

o. a ~ " " " " ' P ' " T ' ". . . . . . . - - , , . . . . . . . . - - . . , . . . -a 5 10

%

15 20

I-

- l-

I-

R V Preaominant ( ~ 50%) 1.0substrate type inr iff le-run areas for

~ 0.8food production.- 0c

A) Rubble or small ...... 0.6boulders (or

> ,+J

aquatic vegeta- :;:::: 0.4tion in spring . 0areas) predom-

co

+J

inant; limited. ; 0.2

amounts ofV' l

gravel, 1arge 0.0boulders, orbedrock.

S) Rubble, gravel,boulders, and finesoccur in approxi-mately equal amounts,or gravel is predom-inant. Aquatic

vegetat ion mayormay not be present.C) Fines, bedrock, or

large boulders arepredominant. Rubbleand gravel ar einsignif icant( ~ 25%).

17

A B

Substra te type

C


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R V O Percent pools during 1.0the late growingseason low water

x 0.8period.OJ"'CC~

0.6e-,~

.....

r- 0.4....

..cn::l

~ 0.2:::JV )

0.00 25 50 75 100

%

R Vl l Average percent vege- 1.0tat ional ground coverand canopy closure x 0.8( trees, shrubs,and OJ

"'C

grasses-forbs) along cthe streambank during ~ 0 . 6

>,the summer for ~allochthonous input.

.....

:;::0.4Vegetation Index = ..c2(% shrubs) + 1.5(%

n::l~

grasses) + (% trees)......

0.2:::JV )

(For streams ~ 50 mwide) 0.00 100 200 300

Vegetation index

R V1 2 Average percent rooted 1.0(Optional) vegetation and stablerocky ground cover

along stream bank. xO.8

OJ"'C

.s 0.6~;::0.4.....

..cn::l~..... 0.2:::JV )

0.00 25 50 75 100

%

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Pool class rating

.

.

~

-

R V1 5 Pool class rating during 1.0the late growing seasonlow flow period. The

~ 0.8rating is based on th e " 0% of the area that con- etains pools of th e three ...... a 6> , 'classes described below:

. j . J....

; ' :0 .4A) ~ 30% of the area .. 0to

is comprised of .j.J1st-class pools. . ; 0.2V I

B) ~ 10% but < 30%of the area is 0.01st-class poolsor ~ 50% is 2nd-class pools.

C) < 10% of the area

is 1 st-c las s poolsand < 50% is 2nd-class pools.

A B C

(See pool class descript ions below)

First-class pool: Large and deep. Pool depth and size ar e suff icient to provide a low velocity resting area fo r several adulttrout. More than 30% of the pool bottom is obscured due to depth,surface turbul ence, or the presence of structures, such as logs,debris piles , boulders, or overhanging banks and vegetation. Or,th e greatest pool depth is ~ 1.5 m in streams s 5 m wide or ~ 2 mdeep in streams> 5 mwide.

Second-class pool: Moderate size and depth. Pool depth and sizear e sufficient to provide a low velo city r est ing area for a fewadult trout. From 5 to 30% of th e bottom is obscured due to surfaceturbulence, depth, or th e presence of structures. Typical secondclass pools are large eddies behind boulders and low velocity,moderately deep areas beneath overhanging banks and vegetation.

Third-class pool: Small or shallow or both. Pool depth and sizear e sufficient to provide a low vel oc it y r es ti ng area for one to avery few adult trout. Cover, i f present, is in the form of shade,surface turbulence, or very limited structures. Typical third-classpools are wide, shallow pool areas of streams or small eddies behindboulders. The entire bottom area of th e pool is visible.

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R V1 6 Percent fines 3 mm) 1.0in riffle-run andspawning areas duringaverage summer flows. ~ 0.8

"'0s::

A=

spawning ......> , 0.6B = r iff le-run . j .J......:;:::: 0.4.. 0to. j .J

. ; 0.2V l

0.0a 15 30 45 60

%

R V1 7 PerGent of stream area 1.0(Optional) shaded between 1000 and1400 hrs (for streams

~ 50 mwide). Do not~ 0.8"'0

use for cold 18 C s::......max. temp. ) , unproduc- > , 0.6t ive streams. . j .J. ....

r -

:0 0.4to. j .J

. ; 0.2V l

0.0a 25 50 75 100

%

R V18 Percent average daily 1.0(Optional) flow during th e seasonof upstream migration of x 0.8

adult st.eel head .Q)

"'0s::

...... 0.6> ,. j .J......

:;:::: 0.4.. 0to. j .J...... 0.2V l

0.025 50 75 100 125

%

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An HS1 based on the concept of a limit ing f ac to r can be obtained for aparticular l i fe stage of rainbow trout, or all l i fe stages combined, byselecting the lowest suitabili ty index (S1) for the appropriate l is ted habitatvariables as i s done in Table 1.

Alternate models and mathematical methods of aggregating S1 1s into l i festage and species HS1 1s ar e presented in th e following pages.

Table 1. Matrix table for d isplay ing sui tabi l i ty indices (S1 I s ) forrainbow trout hab i ta t var iables .

S1 1 s

Variables Adult Embryo Fry Juvenile Other

V1 Maximum t e m p e r ~ t u r e XV Maximum temperature (embryo) XV3 Minimum dissolved 0 2 X XV Average thalweg depth XVs Average velocity (spawning) XV, % cover X X

V7 Substrate size (spawning) X

V. % substrate class XVg Substrate type (food) XV O % pools X X XVl l % riparian vegetation X

V1 2 % ground cover (erosion)aV1 3 Maximum-minimum pH XV1 4 Average annual base flow X

V S Pool class X XV1 6 % fines X X X

V1 7 % shade a

Vl I % average da i ly flow a

aOptional variables.

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Data sources and th e assumptions used to construct th e suitabil i ty indexgraphs fo r rainbow t rout HSI models are presented in Table 2.

Riverine Model

This mode 1 uses a 1 i fe stage approach with fi ve components: adult;juvenile; fry; embryo; and other.

Case 2:

Case 3: Steel head (CAS)

I f V4 or (V i O x V s ) I / 2 is S 0. 4 in either equation, then CA = th e lowestfactor score.

Juven i l e (CJ ) ' CJ variables: V6 ; VIC; VIS; and V2A

Case 1 :

V + VlQ + VlSC =J 3

Or, i f any variable is S 0.4, CJ= the lowest variable score.

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Table 2. Literature sources and assumptions fo r rainbow troutsuitabil i ty indices.

Variable and asource Assumptions

Black 1953Garside and Tait 1958Dickson and Kramer 1971Hanel 1971May 1973Cherry et a l . 1977

Snyder and Tanner 1960Calhoun 1966Zaugg and McLain 1972Zaugg and Wagner 1973Wagner 1974

Randall and Smith 1967Doudoroff and Shumway 1970Trojnar 1972Sekulich 1974

Delisle and Eliason 1961Estimated by authors.

Delisle and Eliason 1961

Thompson 1972Hooper 1973Silver e t al . 1963

Average maximal daily water tempera-tures have a greater effect on t routgrowth and survival than minimaltemperatures. The temperature thatsupports the greatest scope ofactivi ty is optimal. In addition,the temperature range associated withrapid migration rates for adult steel -head is optimal.

The average maximal daily water temper-ature during the embryo and smoltifica-tion development periods that is relatedto the highest survival of embryos andnormal development of smolts is optimal.Temperatures that reduce survival ordevelopment of smolts are suboptimal.

The average minimal daily dissolvedoxygen level during embryo developmentand th e late growing season that isrelated to the greatest growth andsurvival of rainbow t rout and t routembryos is optimal. Dissolved oxygenconcentrations that reduce survivaland growth are suboptimal.

Average thalweg depths that providethe best combination of pools,instream cover, and instream movementof adult t rout are op timal.

The average velocities over spawning

areas affect habitat su i tab i l i tybecause dissolved oxygen is carriedto, and waste products are carriedaway from, th e developing embryos.Average v el oc it ie s t ha t resul t inthe highest survival of embryos areoptimal. Velocities that resul t inreduced survival are suboptimal.

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Table 2. (continued)

aVariable and source Assumptions

Boussu 1954Elser 1968Lewis 1969Wesche 1980

Orcutt e t a l . 1968Bjornn 1969Phillips et a l . 1975Duff 1980

Trout standing crops are correlatedwith th e amount of usable cover.Usable cover is associated withwater ~ 15 em deep and velocit ies~ 15 em/sec. These conditions areassociated more with pool than withr i ff le conditions. The best rat ioof habitat conditions is approximately50% pool area to 50% r i ff le area. Notall of the area of a pool providesusable cover. Thus, i t is assumedthat optimal conditions exis t whenusable cover comprises < 50% of th etotal stream area.

The average size of spawning gravelthat is correlated with th e best waterexchange rates, proper redd construct-ion, and highest fry survival is assumedto be optimal. The percent total spawn-ing area needed to support a good non-anadromous t rout population

was calculated from th e followingassumptions:

1. Excellent riverine t rout habitatsupports about 500 kg/ha.

2. Spawners comprise about 80% ofth e weight of t he popul at ion.500 kg x 80% = 400 kg ofspawners.

3. Rainbow adults average about0.2 kg each.

400 kg0.2 kg

= 2,000 adult spawnersper hectare

4. There are two adults per redd.

2,000 = 1 000 pairs2 '

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Table 2. (continued)


5. Each redd covers ~ 0.5 m2

1,000 x 0. 5 ~ 500 m2 / h a

6. There are 10,000 m per hectare.

1 0 5 ~ ~ 0= 5% of total area,Hartman 1965Everest 1969Bustard and Narver 1975a

Pennak and Van Gerpen 1947Hynes 1970Binns and Eiserman 1979

Elser 1968Fortune and Thompson 1969Hunt 1971

Idyll 1942Delisle and Eliason 1961Chapman 1966Hunt 1971

Oregon/Washington InteragencyWildlife Conference 1979

Raleigh and Duff 1980

Hartman and Gill 1968Behnke and Zarn 1976

The su bs tra te si ze range selectedfor escape and winter cover by t routfry and small juveniles is assumed tobe optimal.

The predominant substrate type contain-ing the greatest numbers of aquaticinsects is assumed to be optimal forinsect production.

The percent pools during late summerlow flows that is associated with theg re at es t t rout abundance is optimal.

The average percent vegetation alongthe streambank is related to theamount of allochthonous materialsdeposited annually in the stream.Shrubs are the best source ofallochthonous materials, followed bygrasses and forbs, and then t rees.The vegetational index is a reasonableapproximation of optimal and suboptimalcondi ti ons for most t rout streamhabitats .

The average percent rooted vegetationand rocky ground cover that providesadequate e ro si on con trol to th e streamis optimal.

The average annual maximal or minimalpH levels related to high survival oft rout are optimal.

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Table 2. (concluded)


V1 4 Duff and Cooper 1976Binns 1979

V1 S Lewis 1969

V1 6 Cordone and Kelly 1961Bjornn 1969Phill ips e t a l. 1975Crouse e t a l . 1981

V1 7 Sabean 1976, 1977Anonymous 1979

V1 B Withler 1966Everest 1973

Flow variations affect th e amount andquality of pool s, instream cover, andwater quality. Average annual baseflows associated with th e higheststanding crops are optimal.

Pool classes associated with th ehighest s tand ing c rops of t rout ar eoptimal.

The percent fines associated with th eh ighes t s tand ing crops of food organisms,embryos, and fry in each des igna ted areaar e optimal.

The percent of shaded stream areaduring midday that is associated withoptimal water temperatures and photo-synthesis rates is optimal. b

The above average daily flows (freshets)associated with rapid upstream m i g r a t i o n ~of steel head adults ar e optimal. Low

flows associated with migration delaysar e suboptimal.

aThe above references include data from studies on related salmonid species.This information has been selectively used to s u p p l e m e n t ~verify, or f i l ldata gaps on the habitat requirements of rainbow t rout .

bShading is highly variable from s i te to si te . Low elevations with warmerc lima tes requi re abundant shading to maintain cool waters. At higherelevations with cooler climates, the absence of shading is beneficial becausei t resul ts in higher photosynthetic rates and warming of water to a moreoptimal temperature.

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Case 2: Steel head (C J S)

Or, i f V O or (Va X V 6 )1/ 2 is ~ 0.4, CF = the lowest factor score.

V .S l

habitat area 10.05 (output cannot exceed 1.0)

Steps in calculating CE:

A. A potential spawning site is a ? 0.5 m2 area of gravel, with anaverage diameter of 0.3 to 8.0 cm, covered by flowing water? 15 cmdeep. For steelhead, increase th e spawning site area from 0.5 to2. 0 m and th e gravel size to 0.3 to 10.0 cm. At each spawning sitesampled, record:

1. The average water velocity over the si te ;2. The average size of all gravel 0.3 to 8.0 cm;

3. The percentage of fines 1.0)

HSI

If only th e l acus tr in e hab it at is ev alu ated , th e HSI = CWO.

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Interpreting Model Outputs

Model HSI scores f or ind iv id ual l i fe stages, composite l i fe stages, or forth e species as a whole are a relative indicator of habitat sui tabi l i ty. TheHSI models, in thei r present form, are not intended to predict s tanding cropsof fishes throughout th e United States. Standing crop limiting factors, such

as interspecif ic competition, predation, disease, water nutr ie nt le ve ls , andlength of growing season, are not included in the aquatic HSI models. Themodels c on ta in physical habitat variables important in maintaining viablepopulations of rainbow trout. I f th e model is cor re ct ly s tr uc tu red, a highHSI score for a habitat would indicate near optimal regional conditions forrainbow t rout for those factors included in the model, intermediate HSI scoreswould indicate average habitat conditions, and low HSI scores would indicatepoor habitat conditions. An HSI of 0 does not necessarily mean that th especies is not present; i t does mean that th e habitat is very poor and thatth e species is likely to be scarce or absent.

Rainbow t rout tend to occupy riverin e habitats where few other fishsp ecies a re present. T h u s ~factors such as disease, interspecific competition,and predation may have 1 i t t 1e affect on the model. When th e rainbow t routmodel is applied to rainbow t rout streams cont a t ni nq few other species andsimilar water quality and length of growing season conditions, i t should bepossible to cal ibrate th e model output to ref lect the size of standing cropswithin some reasonable confidence limits. This possibi l i ty, however, has notbeen tested with th e p re sent model.

Sample data sets selected by the authors to represent high, intermediate,and low habitat sui tabi l i t ies are in Table 3, along with th e Sl l s and HSI'sgenerated by th e rainbow trout nonanadromous riverine model. The model outputscalculated from th e sample data sets (Tables 4 and 5) ref lec t what the authorsbel ieve car ry ing capacity trends would be in riverine habitats with th e l istedcharacterist ics; thus, th e model meets th e specified acceptance level.

ADDITIONAL HABITAT MODELS

Modell

Optimal riverine rainbow t rout habitat is characterized by:

1. Clear, cold water with an average maximum summer temperature of < 22 C;

2. Approximately a 1:1 pool -t o- ri ff le r a ti o;

3. Well vegetated, stable stream banks;

4. Cover ~ 25% of th e stream area;

5. Relatively stable water flow regime with < 50% of th e annualfluctuation from th e average annual daily flow;

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Table 3. Sample data sets using th e nonanadromous riverine rainbow troutHS1 model.

Data set 1 Data set 2 Data set 3

Variable Data S1 Data S1 Data S1

Max. temperature(0C) VI 14 1. 0 15 1.0 16 1. 0

Max. temperature(0C) V2 12 1. 0 15 0.66 17 0.4

Min. dissolved O2(mg/l) V 9 1. 0 7 0.73 6 0.42

Ave. depth (cm) V4 25 0.9 18 0.6 18 0.6

Ave. velocity(cm/s) Vs 30 1.0 25 0.7 20 0.57

% cover V, 20 A 0.95 10 A 0.65 10 A 0.65J 1. 0 J 0.92 J 0.92

Ave. gravel size(cm) V 7 4 1. 0 3 1.0 2.5 1.0

Predom. substratesize (cm) V. 15 1. 0 7 0.7 7 0. 7

Predom. substratetype Vg Class A 1. 0 Class 8 0.6 Class 8 0. 6

% pools V O 55 1. 0 15 0.65 10 0.46

% streamsidevegetation Vl l 225 1. 0 175 1.0 200 1.0

% bank vegetation V1 2 95 1. 0 40 0.6 35 0.5

Max. pH Vl J 7.1 1.0 7.2 1.0 7.2 1.0

% average baseflow V1 4 37 0.8 30 0.6 25 0.5

Pool cla ss rating V 5 Class A 1. 0 Class 8 0.6 Class C 0. 3

% fines (A) V G 5 1. 0 20 0.5 20 0. 5

% fines (8) V G 20 0.9 30 0.6 30 0. 6

% midday shade V1 7 60 1.0 60 1.0 60 1.0

34


44/76

Table 4. Average value method.

Sui tabi l i ty index

Variable

Component

Data set 1 Data set 2 Data set 3

CA

CJCFCE

Co

Species HSI

0.95 0.62 0.37

1. 00 0.72 0.30

1.00 0.65 0.55

1. 00 0.66 0.40

0.96 0.79 0.73

0.98 0.68 0.30

Table 5. Average value, probability method.

Sui tabi l i ty indexVariable Data set 1 Data set 2 Data set 3

Component

CA 0.95 0.62 0.37

CJ 1. 00 0.72 0.30

CF 1. 00 0.65 0.55

CE 1. 00 0.66 0.40

COF 0.97 0.80 0.80

COQ 0.95 0.81 0.68

Species HSI

Noncompensatory 0.94 0.56 0.30Compensatory 0.95 0.70 0.30

35


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6. Relatively stable summer temperature regime, averaging about13 C 4 C; and

7. A relat ively s i l t free rocky substrate in r i ff le- run areas.

HSI = number of at t r ibutes p r e s e ~ t

7

Model 2

A r iverine t rout habitat model has been developed by Binns and Eiserman(1979) and Binns (1979). Transpose th e model output of pounds per acre to anindex as follows:

HSI = mod:l output.of pounds per acrereglonal maXlmum pounds per acre

Model 3

Optimal lacustr ine rainbow t rout habitat is characterized by:

1. Clear, cold water with an average summer midepilimnion temperatureof < 22 C;

2. Dissolved oxygen content of epilimnion of ~ 8 mg/l;

3. Access to riverine spawning tr ibutaries;

4. A midepilimnion pH of 6.5-8.0; and

5. Abundance of aquatic invertebrates.

HSI = number of attr ibutes present5

However, a high elevation lake with optimal habitat will have only afraction of the t rout production of a more eutrophic lake at a lower elevation,

i fno

other fish species a re p re sent in either lake.Model 4

A low effort system fo r p re dic tin g habitat suitabil i ty of planned coolwater and cold water reservoirs as habitat for individual fish species is alsoavailable (McConnell et a l. 1982).

36


46/76


47/76


48/76

Only a l imi t ed number of experimental data se ts have been compiled i n toIFIM p re fe re nc e cur ve s. The development of these curves should be the goal ofa l l new curve development e ffo r t s for us e in IFIM.

An add i t iona l se t of curves i s s t i l l largely conceptual . One type ofcurve under considera t ion i s a cover-condit ioned , or season-co nditioned ,preference curve s e t . Such a curve s e t woul d con s i s t of di f f e r en t depthve loc i ty preference curves as a function or condit ion of the type of coverpresent or the t ime of year. No four th c at eg or y c ur ve s have been developed a tth i s t ime.

The advantage of these l a s t two se ts of curves i s the s i gn i f i c an t improvement in prec i s ion and confidence in the curves when applied to streams s imi la rto the streams where the orig inal data were obtained . The degree of increasedaccuracy and t r a n s f e r a b i l i t y obta inable when applying these curves to d i ss imi la r streams i s unknown. In theory, the curves should be widely t r a n s f e rable to any stream in which the range of environmental condi t ions i s with in

the range of condi t ions found in the streams from which the curves were deve loped.

Avai lab i l i ty of Graphs fo r Use in IFIM

Numerous curves are ava i lab le for the IFIM ana lys i s of rainbow t rou thabi ta t (Table 6) . Inves t iga to rs are asked to review the curves (Figs . 2-5)and mod ify them, i f necessary, before using them.

Spawning. For IFIM analyses of rainbow t r o u t spawning hab i t a t , usecurves fo r the time p er io d d ur in g wh ich spawn ing occurs (which i s dependent onloca le ) . Spawning curves are broad and, i f more accuracy i s des i red , invest i g a t o r s are encouraged to develop t h e i r own curves which wil l spec i f i c a l l yr e f l e c t hab i t a t u t i l i z a t i o n a t the selected s i t e .

Spawning ve loc i ty. Hartman and Galbra i th (1970) measured water ve loc i t i e s0.66 f ee t above 550 redds during April through June, 1966 and 1967, in theLardeau River, Br i t i s h Columbia, and found few redds const ruc ted in areaswhere ve l oc i t i e s were 1ess than 1.0 f ee t per second ( fp s ) ; most redds wereassoc ia t ed with ve loc i t i e s ranging 1.6 to 3.0 fps ( v e l o c i t i e s from zero togrea te r than 4.0 fps were ava i l ab l e ) . Smith (1973) determined t h a t 95% of theredds (n = 51) observed in the Deschutes River, Oregon, were in ve loc i t i e sranging from 1.6 to 3.0 fps; Hooper (1973) measured ve loc i t i e s over redds

(n=

10) which ranged from 1.4 to 2.7 fps in the South Fork of the FeatherRiver, Cal i f o rn i a ; and Orcutt e t a l . (1968) found t h a t average ve loc i t i e s0 .4 f e e t above redds (n = 54 to 68 ) ranged from 2.3 to 2.5 fps in Idahostreams. The SI curve fo r spawning ve loc i ty (Fig . 2) assumes t h at v el oc it i esl e ss than 1.0 or g r e a t e r than 3.0 fps are unsu i tab le fo r rainbow t r ou tspawning.

39


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+'>0o

Table 6. Availability of curves for IFIM analysis of rainbow t rou t hab itat .

Velocitl a SUbstratea,b Temperature a CoveraDepth

Spawning Use SI curve, Use SI curve, Use SI curve, Use SI curve, No curveFi g. 2. Fig. 2. Fig. 2. Fig. 2. necessary.

Egg incubation Use SI curve, Use SI curve, Use SI curve Use SI curve No curveFi g. 2. Fi g. 2. for V7B. for V2B. necessary.

Fry Use SI curve, Use SI curve, Use SI curve, Use SI curve, No curveFig. 3. Fi g. 3. Fig. 3. Fig. 3. available.

Juvenile Use SI curve, Use SI curve, Use SI curve, Use SI curve, Use SI curveFi g. 4. Fig. 4. Fig. 4. Fig. 4. for V 6.

Adult Use SI curve, Use SI curve, Use SI curve, Use SI curve, Use SI curveFi g. 5. Fig. 5. Fig. 5. Fig. 5. for V 6.

aWen use of SI curves is p re sc ri bed, refer to the app ropri at e curve in the HS1 or 1F1M section.

bThe following categories must be used for 1F1M analyses (see Bovee 1982):

1 = plant detritus/organic material2 = mud/soft clay3 = s i l t (particle size < 0.062 mm)4 = sand (particle size 0.062-2.000 mm)5 = gravel (particle size 2.0-64.0 mm)6 = cobble/rubble (particle size 64.0-250.0 mm)7 = boulder (particle size 250.0-4000.0 mm)8 = bedrock (solid rock)


50/76

I

~I .-.0

o 2 3 4 5Velocity (f t /sec)

Coordinates 1. 0x - L

0.0 0. 0 >< 0.80.9 0. 0

QJ"' 0

1.6 1. 0 t :....... 0.63. 0 1. 0 > ,3.1 0. 0

+J

100.0 0. 0...... 0.4..D.tt l+J

~ 0.2U1

1. 0

x - L0. 0 0. 0 x 0.8 -0.6 0. 0 QJ"' 00.7 1.0 t :.......8. 2 1.0 0.6> ,8. 3 0. 0 +J......

100.0 0. 0 0.4 -..D.tt l+J......

0.2 -U1

0.00 2 4 6 8 10

Depth (f t )

1. 0x - L

0.0000 0. 0 0.80.0005 0. 0 xQJ0.0010 1.0 "' 0t :4.0000 1. 0 ....... 0.6

4.1000 0. 0> ,

+J

100.0000 0. 0 ...... 0.4-......

..D.tt l+J

0.2.....~

U1

o. 0 - I - _ _ - - r - _ . . J - _ _ - - . - _ ~o 1 2 3 4 5 6 7 8

Substrate particle diameter (inches)

Figure 2. SI curves for rainbow trout spawning velocity,depth, substrate, and temperature.

41


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Coordinates 1.0x - . L

0.0 0.0 >< 0.835.0 0.0 Q)"' 036.0 1.0 s::. - 0.660.0 1.0 > ,61.0 0.0 ~'r -100.0 0.0 ..- 0.4r -

..cco~

0.2r -: J

(/ )

0.0

-- ~

-.

. o 20 40 60 80 100Temperature (OF)

Figure 2. (concluded)

42


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Spawning D e p t ~ .Smith (1973) found 95% of rainbow t r ou t redds in depthsgrea te r than 0.6 fee t ; Hooper (1973) found depths of redds ranged from 0.7 to1.1 fee t ; Orcut t e t a l . found redds in depths from 0.7 to greater than5.0 fee t ; Hartman and Galbra i th (1970) found the majori ty of redds (n = 550)in depths ranging from 1.6 to 8 .2 f ee t , and the most in tens ive nest diggingoccurred in depths of 5.7 to 6.6 f ee t (maximum depths ava i l ab le ranged from 13to 16 f ee t ) . Therefore , depths less than 0 .6 and greater than 8 .2 fee t areassumed to be unsuitable fo r spawning (although 8 .2 fee t may not be the upperl imi t ; Fig. 2) .

Spawning subs t ra te . Hartman and Galbra i th (1970) found t h a t gravelcomposed of par t i c le s izes ranging from 0.04 to 4 .0 inches in diameter wereu t i l i z ed for spawning, two- thirds of which were from 0 .5 to 3.0 inches indiameter ( p a r t i c l e s i zes to 18 inches in diameter were ava i l ab l e ) . Hooper(1973) found tha t prefer red spawning subs t ra te cons is ted of par t i c les from 0.5to 1.5 inches in diameter, although par t i c les from 0.25 to 3 .0 inches wereu t i l i zed ; Orcutt e t a l . (1968) found t h a t stee lhead favored gravels from 0.5to 4.0 inches in diameter; Coble (1961) s ta ted t h a t salmonids dug redds insubs t ra t es ranging from s i l t to 3-inch diam eter cobble (pa r t i c l e s up to4 inches in diameter were avai lab le) in Lincoln County, Oregon. Therefore ,subs t ra t es consis t ing of par t i c le s i zes ranging from s i l t 0.002 inches) tocobble (4 .0 inches) are considered su i tab le for spawning (t.houqh not necessa r i ly su i tab le fo r egg incubat ion; Fig. 2 ). The par t i c le s i ze range ofspawning subs t ra te se lec ted may be dependent on the size of the spawner.

Spawning cover. No information was found in the l i t e r a t u r e concerningcover requirements fo r rainbow t rou t spawning. The author assumes t h a t coveri s not important, and i t may be omitted from the FISHFIL (Milhous e t a l .1981).

Spawning temperature. Sco t t and Crossman (1973) s ta ted tha t rainbowt r ou t usual ly spawn a t 50 to 60 F; Carlander (1969) s ta ted t h a t peak spawningnear Finger Lakes, New York, occurred a t 42 to 55 F; Hooper (1973) s ta tedt h a t temperatures ranging from 37 to 55 F are des i rab le fo r spawning; andOrcut t e t a l . (1981) found t h a t spawning occurred a t 36 to 47 F in Idahostreams. The author assumes t h a t temperatures rangi ng from 36 to 60 F a r esu i tab le for spawning (Fig. 2), depending on l oca le .

Egg incubat ion. For IFIM analyses of rainbow t r ou t egg incubation

hab i t a t , curves should be used fo r the time period from the beginning ofspawning to 30 to 100 days beyond the end of spawning, depending on locale andwater t emper at ur es (Ca rl an de r 1969). The recommended ana lys i s of incubationwith IFIM i s the e f f ec t ive spawning program, which computes s u i t a b i l i t y ofeach stream cel l based on both spawn ing and incubation c r i t e r i a over a rangeof flows. This program i s explained in a working paper avai lable from IFG(Mil hous 1982).

Egg incubation veloci ty. Evidence suggests t h a t water veloc i ty may notbe important for embryo hatchi ng success i f d i s so 1ved oxygen concent ra t ionsaround embryos are greater than 2.6 ppm (Coble 1961; S i lve r e t a l . 1963;Reiser and White 1981, 1983). At low concentra t ions of dissolved oxygen,

43


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54/76

Coordinates

...... 0.4

0. 6

~ 0.8"'Cc

.......

......

- 1 .1.000.780.190.040.010.01

0.000.00

x0.000.490.981.481. 972.46

2.95100.00

o.0 4 - - - - - - - - " ' T " " " ' - - - - ~ = o p o o I - - +o 2

Mean water column velocity (f t /sec)n == 619

-

10

I I

,4 6

Depth ( f t )n == 642

I

2

I,

o0.0 +---,1'"""'"""'.......,.:= ..... - '1 '---+

0.6

x 0.8Q)"'CC

.......

0.4 -...........

. 0n::l

+J...... 0 .2 -:::l

(/ )

- 1 .0.000.111.001.000.290.130.040.020.010.010.00

0.00

x

0.000.100.821.642.463.284.104.925.747.388.20

100.00

0.6c-,+J

x 0.8Q)"'CC

.......

...... 0.4. 0n::l

+J. ; 0.2( / )

. x . :0.000.000.020.01O. 170.131.001.000.180.000.00

x0.01.02.03.04.05.06.07.08.08. 1

100.0o 1 2 3 4 5 6 7 8

Substrate type (see code key, page 39)n == 597

Figure 3. SI curves for rainbow trout fry velocity, depth,substrate, and temperature.

45


55/76

Coordinates 1. 0x 1 -0.0 0.00

>< 0.832.0 0.00 Q)37.4 0.08

"' 0

c

50.0 0.80.......

0. 6~

56.8 1.00 -f J66.2 1.00

.....

r - 0.469.8 0.80

.....

. 0

77.0 0.00rt l-f J

100.0 0.00.....

0. 2( . / )

0.0

0 20 40 60 80 100Temperature (OF)


46


56/76

Fry depth. The SI curve for fr y depth was developed in the same manneras the velocity curve, using data from Deer Creek (n=103), Cherry and EleanorCreeks (n=404), and Putah Creek (n=135) (Moyle et al. 1983). Depths to 1.7 f twere available 'in Putah Creek; to 6.6 f t in Deer Creek; and to greater than9.0 f t in Cherry and Eleanor Creeks. The fi na1 curve (Fi g. 3) was modifi edbased on the assumption that SI = 1.0 at depths ranging from 0.82 f t (as inPutah and Deer Creeks) to 1.64 f t (as in Cherry and Eleanor Creeks); and thatSI = 0.0 at a depth of 0.0 f t and SI = 0.11 at a depth of 0.1 f t . For depthsgreater than 1.7 f t , Putah Creek was excl uded, and for depths greater than6.6 f t , Deer Creek was excluded from th e analysis.

Fry substrate. The SI curve for fry substrate was generated in the sameway as the curves for depth and velocity. Substrate available in Putah Creek(n=123) ranged from mud to bedrock; and in Deer Creek (n=70), Cherry Creek,and Eleanor Creek (n=404) i t ranged from s i l t to bedrock. The curve (Fig. 3)was modified based on the assumption that SI = 1.0 for cobbles (as in Deer andPutah Creeks) and for boulders (as in Cherry and Eleanor Creeks). Bustard andNarver (1975) also found that age 0 steelhead associated with substrateconsi st ing primari ly of particles from 4 to 10 inches in diameter (cobble) inCarnation Creek, British Columbia, during the winter.

Fry cover. Cover requirements of rainbow t rout fry are unknown by IFASGat this time. The author assumes that substrate is used for cover, and thuscover may be omitted from FISHFIL; or a cover curve may be developed by theinvestigator.

Fry temperature. Peterson et al . (1979), in lab experiments, found thattemperatures preferred by rainbow trout fry (between 1.1 and 1.8 inches in

length) ranged from 56.8 to 58.6 F (n=30). Kwain and McCauley (1978) foundthat age was a factor in temperatures preferred (selected) by rainbow trout,and fry at 1 month selected 66.2 F; at 2 months, 65.3 F; at 3 months,64.4 F; and a t 5 months, 59.7 to 63.7 F. Kwain (1975) found that th e growthrate of fry at 50 F was ten times greater than at 37.4 F. Based on thei nformat ion avail ab1e fo r fry up to 1. 8 inches in 1ength and up to 4 monthsafter hatching, the SI curve for temperature (Fig. 3) i s assumed to be reason-ably accurate. I t will be modified as new information becomes available.

Juvenile. Juvenile rainbow trout range in length from approximately 1.8to 7.9 inches, or from 4 months of age to sexual maturity (usually age II orI I I ; Carlander 1969). Juveniles are probably the most diff icul t l i fe stagefor which to develop cr i ter ia , because of the variability in size.

Juvenil e velocity. Factors whi ch may affect velocity preferences ofrainbow trout include water temperature, size and activity of the individualrout, stream flow, season, habitat avai labi l i ty, species interact ions, andstream location (Logan 1963; Chapman and Bjornn 1969; Bjornn 1971; Everest andChapman 1972; Bustard and Narver 1975; Moyle et al . 1983). Moyle et a l.(1983) observed juvenile rainbow trout (from 2.0 to 4.7 "inches in length) inPutah Creek (n=35), Deer Creek (n=108), Martis Creek (n=58), Cherry Creek, andEleanor Creek (n=300), and in the Tuolumne River (n=45). The maximum velocityavailable in Putah Creek was 2.0 fps; in the Tuolumne River i t was 2.5 fps; inMartis Creek i t was 4.2 fps; and in Deer, Cherry, and Eleanor Creeks i t was

47


57/76

greater than 3.4 fps. Data from all streams were used to generate the velocitycurve (Fig. 4) . Weighted means were calculated for each velocity and thennormalized, with the highest 51 being set to 1.0. The final curve is verysimilar to th e results of Bustard and Narver (1975) who collected Age 0 ( n ~ 7 8 )and Age 1+ ( n ~ 1 2 2 )juvenile steelhead trout in Carnation Creek, Brit ishColumbia, during the winter. They found that juveniles preferred velocities

less than 0.5 fps, and almost no individuals were found in velocities greaterthan 1 fps at 45 F. Gosse (1982), however, found that vel ocit i es preferredby juvenile rainbow trout 9 inches in length) were part ia l ly dependent uponactivity (random or stationary swimming), season, and flow. Gosse found thatth e average mean column velocities occupied by juveniles in low to high flowsduring random swimming ranged from 0.40 to 0.56 fps in the winter and from0.43 to 0.75 fps in the summer. During stationary swimming, velocities rangedfrom 0.66 to 1.18 fps in th e winter and from 1.05 to 2.00 fps in th e summer.Differences may be due in part to differences in th e sizes of th e juvenilesobserved (Chapman and Bjornn 1969).

Juvenile depth. Factors which may affect depth preferences of juvenilerainbow trout are th e same as those which affect velocity preferences. Obser-vations of Moyle e t al . (1983) in Putah Creek (n=36, maximum depths of 1.7 f t ) ,Martis Creek (n=58, depths to 4 f t ) , Deer Creek (n=126, depths to 6.6 f t ) ,Tuloumne River (n=44, depths to greater than 9 f t ) , and Cherry and EleanorCreeks (n=301, depths to greater than 9 f t ) , of juven iles (2.0 to 4.7 inchesin l ength) ind icated substantial variability in depth preferences from streamto stream, with most fish located in depths of 1 to 4 f t . Bustard and Narver(1975), however, found that Age 0 steel head in Carnation Creek, Brit ishColumbia, preferred depths to 1.5 f t , while Age 1+ steelhead preferred depthsgreater than 3 f t . Also, Gosse (1982) found that the average water depthsoccupied by juvenile rainbow trout 9 to 10 inches in length) in the GreenRiver below Flaming Gorge Dam, Colorado, ranged between 10 and 14 f t in th esummer and between 18 and 20 f t in the winter (n=lll to 291). Therefore, i tis easy to see that juvenile rainbow trout may occupy a wide variety of depths,and i t is recommended that investigators develop their own depth curves, orassume that 51 = 1.0 for all depths ~ 2.0 feet (Fig. 4).

Juvenile substrate. Moyle e t al . (1983) found most juvenile rainbowtrout (2.0 to 4. 7 inches in length) over gravel and cobble in Martis Creek(n=53), over cobble and boulders in Deer Creek (n=103), and over boulders inCherry and El eanor Creeks (n=301). The composi te we ighted substrate curve(Fig. 4) shows a preference fo r boulder substrate. In th e Green River, Gosse

(1982) found most juveniles

9 to 10 inches in length) over cobble andboulders during s t.at tonary swimming, but over s i l t and sand during randomswimming. Bjornn (1971) found a correlation between th e movement (outmigration) of juvenile trout and th e lack of large cobble substrate in Idahostreams. Therefore, i t may be assumed that cobble and boulders ar e suitablejuvenile substrate, or curves may be developed that are specific to the areaof in terest .

Juvenile cover. Cover requirements or preferences of juveniles areunknown. I t may be assumed that substrate curve reflects cover requirements;cover curves may be developed by the investigator; cover may be omitted fromFI5HFIL; or, the curve for V

6may be used to represent juvenile rainbow trout

cover requirements (page 16).

48


58/76

Coordinates

0.6

x0.000.490.981.481.972.463.443.50

100.00

. x . :1.000.990.590.240.080.020.020.000.00

1. 0 - r - _ - . . . I - - - .........------f-

x 0.8Q)- 0c

.....

-,.... 0 .4.,.....0

re:s+.>

.,.... 0 .2:::sl/ )

2o. 0 - I- ........... ..--.,.......-- .............:::=:;::::i.

oMean water column velocity (f t /sec)

n = 546

.,....

.,.... 0.4

0.6~

x 0.8Q)- 0c.....

.0

re:s+.>

. ; 0.2l/ )

- L

0.01.01.0

x

0.02.0100.0

0 .0 ............. . . . . . - - - . - - ................ - - - . . . . +

o 2 4 6 8 10Depth (f t )n = 565

x0.02.03.04.05.06.07.08.08. 1

100.0

.x.:0.000.000.020.110.210.771.000.470.000.00

~ 0.8- 0c.....e-, 0.6+.>.,....

~ 0.4re:s+.>

. ; 0.2l/ )

0.0 -r - _ _ IIIIIIIl:i-....--......--.--_ __+_o 1 2 3 4 5 6 7 8

Substrate type (see code key, page 39)n = 457

Figure 4. SI curves for rainbow trout juvenile velocity, depth,

substrate, and temperature.

49


59/76

Coordinates

x0. 032.050.072.084.0100.0

1 -0.00.01. 01. 00.00.0

x 0.8Q)"' 0C

.......

> , 0.6~

.....

..... 0.4.. 0

ro~..... 0.2::JU1

o. 0 4 - _ . . . . . . " " ' - . . . . .~

o 20 40 60 80 100Temperature (oF)


50


60/76

Juvenile temperature. There has been a great deal of variability amongresults of studies undertaken to determine temperature preferences of juvenilerainbow trout. Cherry et al , (1975) found that temperatures selected andavoided were a function of acc limation tempera tu re ; that rainbow juvenilesselected temperatures ranging from 53 to 72 F when acclimated to 43 to 58 F;and that the lowest avoidance temperature was 41 F and the highest avoidancetemperature was 77 F at th e given accl imation temperatures. Coutant (1977)l isted preferred temperatures of 64 to 66 F and 72 F, and avoidance tempera-tures of 57 and 72 F. Lee and Rinne (1980) found th e cr i t ical thermal maximafo r juveniles to be 84 F. McCauley et al . (1977) stated that acclimationtemperatures had no significant effect upon preferred temperatures ofjuveniles, which ranged from 50 to 55 F. Kwain and McCauley (1978) foundthat temperature preferences were a function of age, and that juvenile rainbowt rout 12 months af ter hatching preferred a temperature of 55 F. No studieswere found which addressed maximum growth rate/low mortality temperatures. Afinal curve was drawn based on th e limited information available and profes-sional judgment (Fig. 4).

Adult. For th e purposes of th is model, rainbow trout are considered tobe adult when they are greater than 7.9 inches in length at age I I or I I I , andsexually mature (Carlander 1969).

Adult velocity. Moyle et a l . (1983) collected rainbow trout adults(which they defi ned to be > 4.7 inches in 1ength) from Deer Creek (n=104;maximum veloci ty> 3.4 fps), Cherry and Eleanor Creeks (n=360; maximum velocity> 3.4 fps), and th e Tuolumne River (n=93; maximum velocity = 2. 4 fps). Theresulting weighted normalized curve suggests that preferred mean column veloc-i t ies ar e near 0.5 fps. Lewis (1969), however, found a positive correlationbetween rainbow trout density and water velocity of 1.65 fps. Gosse (1982)found that rainbow trout generally tended to reposition themselves in thewater column as streamflow changed, and that fish nose velocity varied lessthan mean column velocity with changes in streamflow. Average fish nosevelocities for stationary swimming during th e winter ranged from 0. 7 to 1.0 fps(n=640); during th e summer they ranged from 0.9 to 1.1 fps (n=224); for randomswimming during the winter they ranged from 0.5 to 0.7 fps (n=308); and duringthe summer they ranged from 0.4 to 0.6 fps. Average mean column velocit iesfor stationary swimming during th e winter ranged from 1.1 to 1. 7 fps (n=606);during th e summer they ranged from 1. 5 to 2.0 fps (n=219); for random swimmingduring th e winter they ranged from 0.6 to 0.8 fps (n=308); and during th e

summer they ranged from 0.6 to 0.7 fps (n=l71). Therefore, the fi na1 curve(Fig. 5) ref lec ts the range of mean water column velocities preferred by adult(> 5 to 9 inch lengths) rainbow trout, although preferred fish nose velocit iesranged from 0.5 to 1.1 fps. An invest igator may choose to develop new curvesspecif ic to the area of in teres t .

51


61/76

Coordinates 1.0x . x . :0.00 0.81 >< 0.8)0.50 1.00 "' 0t::2.00 1.00 ~2.46 0.02 > , 0.62.95 0.02

~

,....

3.44 0.01 ...... 0.4.03.50 0.00 to+. l

100.00 0.00 ......::::l 0.2')

0.0a 2

Mean water column velocity (ft /sec)

1.0 .x . s : I0.0 0.01.5 1.0 >< 0.8- -)10.0 1.0 "' 0t::100.0 1.0 ~

> , 0.6-.j J......

J,....

0.4....... 0to+. l

......

0.2-:::lV ')

0.0 I T T

a 2 4 6 8 10Depth ( ft)

1.0x . s . :0.0 0.001.0 0.01 >< 0.82.0 0.01 Q)"' 03.0 0.75 t::~ 0.65.0 0.75 > ,6.0 1.00

+. l......

7.0 1.00 ,.... 0.4.....8.0 0.20 .. 0to8. 1 0.00 +. l...... 0.2

100.0 0.00 ::::lV ')

0.0a 2 3 4 5 6 7 8

Substrate type (see code key, page 39)

Figure 5. S1 curves fo r rainbow trout adu lt veloc ity, depth,substrate, and temperature.

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Coordinatesx

0.032.055.470.084.2100.0

- . L0.00.01.01.00.00.0

>< 0.8OJ

" 0C

-- 0.6t ';:: 0.4. r -.0

ta. ;J

' r - 0 2:::::l ( / ' )

o 20 40 60 80 100Temperature (OF)


53


63/76

Adult depth . Depths most u t i l i zed (n=361) in Cherry and Eleanor Creeksranged between 1 .5 and 2 .5 f t , whereas depths most u ti 1 i zed in the TuolumneR iver ranged between 2.5 and 4.1 f t (Moyle e t a l . 1983). Adults in the GreenRiver, however, primari ly u t i l i zed depths ranging from 12 to 17 f t (Gosse1982). Therefore , i t may be assumed t ha t the SI = 1 .0 fo r a l l depths g r e a t e rthan 1.5 f t (Fig . 5 ) , or curves may be developed t ha t are spec i f ic to the area

of i nve s t i ga t ion .

Adult sub s t r a t e . Adults (> 4.7 inc hes) in Deer Creek (n=96) primari lyu t i l i z e d cobble; in Cherry Creek and Eleanor Creek, and the Tuolumne River(n=448) they primari ly u t i l i zed boulders (Moyle e t a l . 1983). In the GreenRiver, adul t s (> 9 to 10 inches in l eng th ) u t i l i z e d Gobble and bou ld er s d ur in gs t a t i ona ry swimming; and s i l t , sand, and boulders during random swimming(Gosse 1982). The f ina l curve (F ig . 5) i s based on professional es t imat ion .

Adul t cover. Su ff i c i en t information was not loca ted fo r the developmentof a curve fo r adu l t t r ou t cover r e q u i r e m e n ~ s .Lewis (1969) found a pos i t ive

co r r e l a t i on between the amount of cover and adu lt dens i ty . Butler andHawthorne (1968) found t ha t rainbow t rou t had l e s s a f f i n i t y fo r cover thanbrook or brown t rou t . The i nves t i g a t o r has several opt ions when consider ingcover. Cover may be omitted as a model var iab le ; cover curves may be developedindependent ly ; i t may be assumed t ha t cover i s adequately addressed bysubs t r a t e and depth ; or the curve fo r V6 (page 16 ) may be used to rep resen t

adu l t cover requirements .

Adul t temperature . Prefe r red temperatures of rainbow t rou t adul t s havebeen found to be 55 .4 , 59 .0 , 61 .7 , 64.4 , and 66.0 to 70.0 F (Coutant 1977;Sp iga r e l l i and Thommes 1979). Temperature se lec t ion may be a funct ion of

a cc limat io n t emper at ur e, s ize of f i sh , and time of year. Lee and Rinne (1980)determined the c r i t i c a l thermal maxima a t 84.2 F. The f ina l curve (Fig . 5)i s based on t h i s informat ion.

REFERENCES

Adams, B. L ., W. S. Zaugg, and L. R. McLain. 1973. Temperature e ffec t onpa rr -smo lt t ra n sf o rma t io n in s teelhead t r ou t (Salmo ga i r dne r i ) as measuredby g i l l sodium-potassium s t imula t ed adenosine t r iphospha tase . CompoBiochem. Physiol . 44A:1333-1339.

1975. Inh ib i t ion of s a l t water surviva le leva t ion in s teelhead t rou t (Salmo ga i r dne r i ) bytempera tures . Trans. Am. Fish . Soc. 104(4):766-769.

and Na-K-ATPasemoderate water

Alabaster, J . S . , D. W. M. Herber t , and J . Hemens. 1957. The surviva l ofrainbow t r ou t (Salmo ga i rdner i Richardson) and perch (Perca f l u v i a t i l i sL.) a t var ious concentrat ions of dissolved oxygen and carbon dioxide .Ann. Appl. Bio l . 45:177-188.

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Allen, K. R. 1969. Limitations on production in salmonid populations instreams. Pages 3-18 in T. G. Northcote, ed . Symposium on salmon andt rout i nstreams. H. R.-MacMi 11 an Lecture Seri es in Fi sheri es , Univ. Br.Columbia, Vancouver.

Baxter, G. T., and J . R. Simon. 1970. Wyoming f ishes. Wyo. Game Fish Dept.Bull. 4. 168pp .

Behnke, R. J . 1979. Monograph of the nat ive t routs of the genus Salmo ofwestern North Ameri ca. U.S. Fi sh Wi 1d l . Serv. , Regi on 6, Denver, CO.215 pp.

Behnke, R. J . 1983. Personal communications. Associate professor, ColoradoState Univers i ty, Fort Coll ins , CO.

Behnke, R. J . , and M. Zarn. 1976. Biology and management of threatened andendangered western t rou t . U.S. For. Servo General Tech. Rep. RM-28.'4 5 pp.

Bell, M.C. 1973. Fisheries handbook o f en gin ee rin g requirements and biolog-ical c r i t e r i

habitat suitability rt

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