JamesH. Johnsonr Nez PerceTribal FisheriesDepartment P.O. Box 365 Lapwai, 83540

Comparative Diets of Paiute Sculpin, Speckled Dace, and Subyearling Steelhead Trout in Tributaries of the Clearwater River, ldaho

Abstract

The food habits of Peiure scL pin \ 6ttui beld;ns;) , spe&led dace (Rbinichthls osculu\ , and, subyeariing steclhead t.our lSalnn gandneti) were examined during summer and carly fall when rhev coe*iai in riffles. A rotal of 1q6 Paiutesculpin. 186 speclled da.c. dnd lt4sub;earingsrcrlhtad trout from six tributnrier of the Cl€.arwar.c Rjver, jn North Centrat Idaho, wc.c used for analysis. Paiute sculoin fed exclusrvely on autochthonous material whereas steelhead utilized both autochthon- ou! (+2-8i percenr, i:65 pefcenr) end allochthonous (10-58 percent, -:14 percent) foods Detri- ru< 14t'--- peftenr, x-oo perccnr/ was rhe major i"od ir rhc dier of the.pe(L cd dat. Oterlap io diet of specllcd dace with both Paiute sculpin (0.r02-o.il6, i:0.I6rt and \ubvc.rling steelhead (0.062-0.250, i-0.161) was very low. Diet overlap betweeo Paiute sculpin and subyearling steel- hcad was moderate (0.489 0.5t1) in five oI the streams and hish (0.869) in one. The data suggest tbat during diurnal periods there is definite dclineation io the foods caten by these three species when they coxist in riffle habitats durirg the summer and fall.

Introduction Competition for food resourcesmay be facilitated when differeot speciesoccupy rhe same microhabitat. In rhese instances,competitive inreractionsmay be reduced if sympatric{ishes 1) feed on

Methodsand Mateiials Fisheswere collectedfrom I Ausust to 6 Octobet 1982 in six tributaries of the Clear-

lPresentaddress: Department of Fish and \Y/ildlife, i06 S. \{/. Mill Street,P. O. Box 1501, Porc land, 97208.

Northwest Science,Vol. t9, No. 1, 1985 water River in North Ceotral Idaho. The six streams,Bedrock Creek,Big CanyonCreek, Cottonwood Creek, Jacks Creek, Laprvai Creek, and Mission Creek, dischargeinto the ClearwaterRiver within rhe Nez PerceIndian Reservation( Fig. 1). A generaldescrip- tioo of rhe collecrion sire of eachsrteam is presentedin Table 1. Fisheswere presetvedin 10 percent formalin after being stunned with an electro- shocker.Diet composition was determined on a dry weighi basis from estimatesde-

EDROcx CR. DWORSHAK RESERV

NEZ PERCE IND,AN RE5ERVAIION

Figure 1. location of the study streams within the Nez Perce Indian Reservation. Idaho.

rived for individual prey taxa. \Thenever possibie,aquatic invertebrateswere identified to family, terrestrial invertebratesto order, and fish remains to species. Diet overlap berween Paiute sculpin, speckleddace, and subyearlingsteelhead trout in eachstream was calculatedusing the equation of Horn ( 1966) : s ar-) S .!..v

ss )X" l-: Yr" i-1 i:l vrhere C,f,: overlap val re s: food categories X; - proportion of the total diec o{ fish species X conoibuted by food caregoryi Yi.- ptoportion of the total diet of fish species Y conrribureJby i.,o,lcaregory i IThen employing this equation diet ovedap vahies (C),) can range from 0 (no overlap) to 1 (complete ovedap).

Johoson TABLE 1. Siream lengih (km), collection location (km from slrem mouih), average stream width (m), maximum temDeraiure (Co), a r waier velocitv (cm/s) Ior siuilv sbearns antl sla- tions. Estimries at each collectioD locnlion for stream wiilih, ma'ximum t€mp€rlrure an'l velociy represent late sumer condilions

15 2 3.ri )20 ' 25.9 Bis Canyon Creek 14 9.1 34.6 Cotionwood Creek 26 7 3.6 23" 17.8 13 E 2,3 23. 74.7 45 25 5.5 2'.1o 33.9 34 22 3.5 26" 19_5

TABLE ?. Number oi tish examineal, mean leneith a-nd size ra-nae (TL, mm), and date oi collection, r.om six tributaries ol the CleaNatcr River, Idaho.

Beahock Creek 08/03/82 12 50-? 44-63 40 6E.3 58,?8 Steelhead 0+ 20 ?0.6 59-83 Lapwai c-reek 08/0:t/lJ2 55 65.9 53-97 60 68.0 54-87 Sieelheaal0+ 83 63.0 53-E5 09/23/42 27 64.0 46-98 10 72.0 63-?9 Sieelheaal0+ 20 71.8 60-92 0r/28/32 43 66.1 54-89 16 77.7 45-94 Steelhearl 0+ 2l 70.3 71 92 '1J.L Bis Canyon Creek 70/01/82 30 59-70 40 73.4 62-83 24 84.2 66-100 4$ 102 CononwoodCreek 10/06/82 29 65.0 speckled Dace 20 57.4 40- Eii 26 90.5 ?6-102

Resulls The diets of 196 Paiute sculpio, 186 speckled dace, and 194 subyearling steelhead trout from six ClearwatetRiver tributarieswete usedfor aflalysis(Table 2) The three species were collectedin sufficient numbersto quantify thafu diets in each of the six sffeams' Sample sizes from individual streamsconsisted of a low of 57 fish from Jacks Creek to a high of 198 fish from I-apwaiCreek ( Table 2). Paiute scr:lpin fed exclusively oo autochthonousmaterial. HydloPsychids (150- (17.1'28-5 40.9 percent,V-27.2 Percent), chirooomids percent, --237 Percent)' aod baetids (4.4-25.1 percent,x:14'5 percent) were the ma,or prey consumedaod were the only taxa that were rePresentedin the diet of Paiute scllpin in each of the six streams ( Table 3). Additional benthic taxa which were imPoftant in the diet of Paiute sculpin were perlodids and elmids ( four streams), tipulids (three streams), pedids (two streams),and sialids (one stream). Fisheswere only found in the diet of Paiute sculpin in one srearn. In Big Canyoo Creek comPosed 41.4 percent of the diet of Paiute sculpin. The speciesis apparently caooabilisticsince approximately 80 perceot of the fish remains in the diet (one-third of the total diet of Paiute scu\>in in Big CaoyonCreek) was identified as Paiute sculpin. The majot component in the dia of speckled dace was detritus (46.1-77.0 percettt' x-65.5 percent) ( Table4). Chironomidlawae (.3.1-17.5Perceot, i:117 Percent)

Comparative Diets of Paiute Sculpin TABLE 3 r'erceni at.v weisht dietarv composiuon of paiute sculoin in rributaries oi the crerrwater River, Tda.ho.Only those Drey taxon nhich composed at teast Z percent of the aliei of Paiute sculpin in one or more of ihe st eams :!re inclurleal.

Bic Carwon Coilonwootl Creek

19.4 9.2 8.4 3.3 3.4 15.9

Baetialae 25.0 9.1 10.4 12.7 25.1 Hepl:rseniidae E.1 7_4 2.9 UnidebiiJied 2.0 1\7

Brachycentridir"e 2.5 clossosomatidae 0.3 4.1 Helicopsychidae ; HydroDsychiilae * 40.9 326 23-0 ; 15.0 Limnephilidae 2.8 ;

Sialidae 9.0

Elmiilae 3.6 13_3 0.6 7.2 Diplera (L) Chironomida€ 21.4 17.7 28.3 19.0 26.9 2Ii.5 Simuliidae 0.8 Tipulidae 12.6 1.2 1.1

C. beldingi Unirlentiiied 8.3 ; ; 2.2

TABLE 4 Pe.ceni drv wekht ari€rarv composirion or speckred arace in tributades oI ihe clearvaier F,iver, Idaho. Onty those Drey tdon which comDoseit ai teast 2 percen! ot lhe cliet oi speckted itace in one or more of the streMs are incluileat.

Bic Beilrock kLp'wai Mission Canyon Creek Creek Creek

Perlodidae 5.2 6.9

Baeiidae 10.9 24.0 5.4 4.9 Heplaseniidae ; 1.5 Unidenlilied 1.4 5.5

Hydropsychidae 5.2 4.3 5.6 12.\ Dipiera Chironomidae (L) 14.2 9.4 17.5 \0.7 3.1 11.3 Tipulialae 7.1 '1.1 Detriius 77.0 57.5 65_5 ; 72.7 1.9 0.5

'I€rrestrirl rl'lxon

2.2

4 Johnson were the principal benthic prey consumed and were present in the diet of fish from all six sueams.Baetid nymphs were the secondraokiog prey (0-24.0 perceot,x-9.9 p€rce[t), occurliog in the diet of dace in five of the sffeams. Hydropsychids ( four sueams), perlodids and tipulids (two streams) and tabanids (one stream) also con- tributed substantially to the diet of speckled dace. Allochthonous foods were alrnost completelyabsent from the diet. Subyeading steelhead trout fed heavily on allochthonous material. Terlestrial in- verrebrat€scomprised from l0.l-57.7 petcent (x:342 percent) of the diet of sub- yearling steelheadin rhe six streams(Tabte 5). The main terrestrial iovertebratescon- sumed by steelheadwere homopertans (x:8.7 percent), coleopterans(i:6.5 per- cenr), arachnids (x-4.6 oercent), hemiprerans (x:4.0 percent), and hymeno- pterans (- : 3.7 percetrt). No single order of terresffial invertebrates were represented in the diet of steelheadin each of rhe six streams.Ctrironomids (14.1-19.7 percent,

TABLE 5- Perceni dry weisht dietaxy coq$silion ol subyearlins steelheaal troul in iribuiaries oi the Clearwater Liver, Idaho, Only those prey iaxon which composed at leasi 2 perceni oI the iliei ol subyearling sieelheaal trout in ot the sirea,ms axe includeal.

Bic Bedrock LaDwai Mission Canyon Coltonwooal Creek Creek Creek Creek Creek

0-5 1.3 12.3

B.],eiid,r.e 13.6 5.7 6.9 30.7 6.5 79.2 HeplaseDiialae 1.1 Unideniiiied 14 2.6 1.3

Hydropsychidae 13.2 8.6 9.3 9.2 16.4 11.7 Unideniili€il 2.$ 2.\ 0.5 Di era Chironomidae (L) 12.5 16.3 19.5 7.2 $6.1 t't.7 Chironomida€ (P) L.2 3.7 7.t 11.4 5.5 Chironomidae (A) 0.4 2.] 2.2

TiDulidae 7.3 :: ; Scaiophasialae 0.9 ;

3.6 4.2 Detrilus 7.5 * 6.5 1_3 3.1 42.3 56.2 55.8 69.3 E1.3 89.9

Terrestrtd Taxon 12.6 1.5 10.8 3.2 9.9 2.7 ; 32.5 3.3 1.4 ; 0.6 9.2 Diplera 2.0 3.5 - 0.4 ; 15.u 0.9 5.6 44.7 140 15.4 7.9 2.7 '1.6 8.7 3.3 ; 3,3 Total Terrestrial 57.7 t* ; 18.? 10.1

I-LaIvae; P-Pupa ; -A. AdulL

C-omoarativeDiets of Paiute Sculoin x:15.8 percent), tnetl.ds (5.7-19.2 percenr, x:13.8 percent), and hydropsychids ().2-16.4 petcerc, x:11.4 percent) were the primary aquatic invert-ebratesutilized by subyeadingsteelhead, Diet qvedap was estimated berween the three species for each of the six srrearns. Becauseof the large contribution of derirus in the diet of speckleddace, diet overlap values between dace and Paiute sculpin (0.102-0.336, x- 0.167) and subyeading steelhead (0.062-0.25O,x-0.161) were very low (Table 6). Diet ovedap between

TABLE 6. Dietary overlap values (Cl.) amons Paiute sculpjn, sleckled dace, and subyearlins sreol- head lroul in lfbuLaries of the Clearwaier River. Idrho.

Paiute Scuipin-SDecklial Dace 0.3?6 0.207 Bis Canyon Creek 0.12u 0.120 0.111 Cotlonwood Creek _ 0.t02 X = 0.16? Faiute SculDin -SLeelhead 0 + Cotton$-ood Creek 0.869 Big Canyon Creek 0_553 0.552 0.5t2 0_51? _ 0_489

Steelhead 0+ -SDeckleil Dace 0.250 Coilonwood Creek 0.247 Big Canyon Creek 0.1?E 0.145 0.085 _ 0.062 X = 0-161

Paiute sculpin and subyearling sreelheadwas moderate (0.489-0.553) in five of the streams.Mutual predation on pedodids, baetids, hydropsychids,and chironomids by Paiute sculpin and steelheadin Cottonwood Creek resulted in the only high diet over- lap value obsewed,0.869.

Discussion Collections of Paiute sculpin, speckled dace, and subyearling steelhead in the six Cleai- warer River tributaries generally reflected a similar pattern of distribution of these species io the basin as had been previously reported ( Maughan 1976, Maug$at and, Saul 1979). Observationsof microhabitat urilizarion indicated that during the period when collectionswere made all three speciespredominated in riffle areas,The utiliza- tion of riffle areasby Paiute sc'ulpin (Jones 7972, Moyle 1976, Finger 1982), speckied dace ( Moyle 1976, Schreiberand Miockley 1981, Baltz et al. 1982), aod subyeading steelheadtrout (Hartman 1965, Johnsonand Ringler 1980) is well documented. The most thorough examinationof the diet of Paiute sculpin in a lotic environmenr was colducted in SagehenCreek, C-alifornia (Dietsch 1959). In SagehenCreek benthic insectscomposed approximately 99 percent of the diet of Paiute sculpin with various prey taxa being seasonallydominant in the dier. Diersch (1959) afso found evidence that differencesoccurred berween the diets of small ( ()!mm) and large ( )80mm) sculpins.

Johffon Paiute sculpins in the Clearwater River tributaries, like those io SagehenCreek, fed most heavily on aquatic insects,did not utilize terrestrial invertebrates,and except in Big CrnyonCreek. sere not piscirorou.. Becauseof the difficulty in separatingalgal {rotr detritai material from the stomachs of speckleddace for dry weight analysis,both of these items rvete grouped as detritus. Jhingran (1948) found detritus to be a majot comPonentin the diet of speckleddace during summer. Io the fall, dace have been shown to feecl on unidentifiable fibrous material (Jhingran1948) and algae(Li and Moyle i976, Pedenand Hughes 1981). However, nlost investigatorsexaminiog the food habits of speckleddace describethe minnoq. as a predator on benthic insects (Jhiogran 1948, Peden and Hughes 1981, Schrieberand Miockley 1981,llakz et al. 1982)- The principalbenthic taxa that have been observedin the diet of dace are baetids,hydropsychids, and simuliids. Subyearlingsteelhead (rainbow) trout feed nost heavily on benthosduring summer and early fall (HaonLrksela1973, Tippets and Moyle 1978, Johnsonand Ringler 1980, Johnson 1981, Johnson and Johnson 1981). Horvever,at least duting diuroal periods, terrestrial invertebrateshave been repolted to comprise a substantial Portion of the diet of subyeatlingsteelhead (Johnsoo and Rinlller 1980, Johnson 1981, Johnson and Johnson 1981). Although most of the diet of subyearlingsteelhead trout in Clearrvater River tributaties was composedof autochthonousmaterial, allochthonousprey irems (*- 34 percent) conrtibuted a considetableamouot to the diet. Only one of eighteenobservations of diet ovedaP belweeo Paiute sculpin, speckled dace, and subyeatling steelheaduout io Clearwater Rivet tributaries exceeded0.56. Diet overlap valuesof 0.60 or more ar geenerallythought to indicatesimilar cliets (Zaret and Rand 1971. Fuller aod Stewart 1977). The data show that there is defioite delinea- don io the foods eatenby these three speciesduriog diurnal petiods when they occupy rhe same habitat in Ciearwatet River tributaries. This situation cor-rldptevail from shortly {ollowing steeiheademergence in lune until terrestrial invertebraresbecome less availabie,possibly during mid to late autumfl. Becauseof the scarcity of detrital and allochthonousmaterial, diet overlap between Paiute sculpin, speckled dace, and sub- yearling steelheadoverrvinteting in tiffles would be expectedto be higher than observed in this investigation. However, since food consumption rates are diminishecl at this time and standing crops of benthic insectsare generailyat rheir Peak (Hynes 1970), competirion for food betrveen these benthic fishes might not be severe. By spring juvenile steelheadrvould no longer be ptesent io high densitiesin riffles; they would be occupyiog areashaving more covei. Diet overlap between speckleddace and Paiute sculpin in Cleatwater River tribu- taries was substantiallylower than irad been previously reported betrveen dace and two other speciesof sculpins.Li aod Moyle (i976) and Bahz et al'. (1982) for.rnda moderate overlap in diet between speckleddace with Pit sculpins (C. P;te iist rnd rif{le sculpins (C. gxlons). These studies reported that bodr dace and sculPins fecl similarly on benthic insects.Based upoo the benthic comltsjtion of the diet of speckled dace, Jhingran (1948) judged that dace were competitors with subyearling chinook salmot (Oncorbynchtr tibduytJcba) and steelheaduout. However, the larger contribu- rion of detrital material in the diet of speckleddace in this study led to low overlapsrvith both sculpin and steelhead.Hannuksela (1973) obserwedthat the summer diets of moftled sculpins (C, baitcti) and jrlenile tainbow trout s/ere simiiat in a tributary ot Lake Sr:perior.Except for the larger contribution of allochthonousmatetial in thc cliet of

C,omparativeDiers of PaiuteSculpin steelhead in Clearwater River ffibutaries, results of the two studies are comparable. Besides seasonalvariation in diec composition, anothet factof ro conside{ when evaluating either diet ovedap or competition between fishes is diel feeding periodicity. Paiute scuipio are mosr acive at night (Fioger 1!g2) and ur" r"port".lly no.rornul (Moyle feeders 1976). Li and Moyle (1976) showed speckleddace to be primarily a_diurnal feeder with peak feeding occurring at 2000 h. lohnson (19g2) reported an identical peak (i.e., 1600-2000h) for blacknosedace (R-. atrarltJ/tr) in a tributary of Lake Ontario. The food consLrmptionof subyearlingsreelhead has been shown to in- creasesubstantially from 1200-2000h wirh peak feeding occurring from 1600-2000h in a tributary of the york SalmonRiver, New (Johnsonand Johnson 19g1). Thesedata indicate that Paiute sculpin are nocturnal feederswhereas speckled dace ancl subyea ing steelheadtrout are principally diurnal feeders.Since the peak food coosumition oi Paiute sculpin occursar a different time than either specklJ dace or subyeadingsteel- head trout, competitive interactions for food may be reduced between these species and sculpins. The large contribution of terrestial invertebratesin the diet of subyelrfing steelhead suggeststhat rhis speciesis feeding heavily on drift. Conversely,the detrial and benthic componenrsin the diet o{ speckleddace indicate that this speciesis primarily a benthic forager. Differeoces in foragiog areasof dace and steelheadtherefore could offset any competitive interactionscreared by diurnal feeding peaksfor both species_

Acknowledgmenls I wish ro thank P. A. Kucera, M A. Bear, K. Carter, D. R. Cross,and C. L. W.ebbfor their assistaricein the fieid, A. Gould J. fot typing the manuscript,and E. Z. Johnson for reviewing the manuscript.

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Comparative Diets of Paiute Sculpin