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<br />'..
<br />
<br />2-3
<br />
<br />influenced by any single parametpr, but by varying riegrees ot all l1ydraul ic
<br />funct.ions.
<br />
<br />~.5 ciases
<br />
<br />A major source of bias in habitat utiliziltion curves occurs during
<br />measurer.1('nt of habitat partllileters.kSy restricting sampling to specific
<br />habitat types, fish preference can appet!r to bE limitco. To minimize or
<br />avoid this bias, snmplinq shoula occur in all habitat types and hydraulic
<br />conditions availabl~ to insure that the wide range of fish use is r-etlected.
<br />
<br />Sc!'1ple bitiS enn also occur es C! result or 9~ar sc'lEctivity, saJr:pling
<br />technique, or oDs~rvation technicue. Cert?in Cnpturp c~~rs may cause d fish
<br />T.Cl move fro!!' its prehrrec t1cbitilt to (! less (iE>sirablp ont' bdore it is
<br />Ci1pturp.c. Thus, r.:eilsurements tClken at t!1e cC'pture 1 oCi'ltion ~?y not refl ect
<br />:~~ rost suit~blc h?bi~Dt for th0 sp(cics.
<br />
<br />In small, ch,;r streams, conditions tor r.C':tl; col1c,ctior. lJr~ cc,nsidt:>rea
<br />optiliurn cec3usf;; tr:c locrttion of a fisl1 Cfn often be pinpointed hy visu?l
<br />cbsr-rv2tion froJ1'l thp streenbGnk, anC' tt:e ':Jater /"!epth, velocity, sLJbstr~te
<br />~ype ant tr~peraturF associatp~ wit~ its l0c~tion accurately measurert~
<br />Cnn'lf'rsely, (lata collE'ction in l,'rqe T.llrbic! rivprs, sl1ch 2S till:> Colcrfldo and
<br />Grl'l~r Rivers, is (Irnf.:' unCpr less t.han optir:w" concitions. ~ince a fish
<br />Ci:nnot he seen in the \'J?ter, it rust be cart!lred win: either active
<br />( e 1 E: C ': ro f i s n i n ~ , s ( i n e s ) 0 r pc s s i v j:.: (J [ ? r S (~i 11 n r: 1'. S, t. r (l r"fT1 E: 1 net s , f y k e
<br />n~ts). Fish c(,lIght "litll flctive 9~i':rS mey IX driver frOf11 prefel~rt:ld habitat
<br /><Jl:ring capture, end those cau9ilt with pi.ssivr' ~f::crs r:"'rY Cf r:'('vi""~ between
<br />~crF' Ces iran 1 f haoi tat typ~s. Ei ther scene ri 0 mr:y i n~ t'CdUCl bi as into
<br />S"r"fllin~ the?": ("?n rlistort accurate tvb;~(1t utili:."tion curvc's. These bias€>s
<br />~rc tt"if~ prindry rr.ason th0t thr- IFH-. hllS fJrer:tfr' l~ccep~drc~f: in Slilol1, cl(ar
<br />ST.r('.=~s. 11'1 file!, the concfpt of Lrhiti1t l'tilivtior cur\'~s .1r'l1 tT:f IFl;'!
<br />i~GvP rot recn tes~r,d iT! ni~ riVft'S such cS th~ Co-Icr,"(!c, breU1 and Yarpa.
<br />
<br />To cvoic the possiblE biaSes ("JuseG by ~ct.iv(' ?nd passivE' g(ars in
<br />1 ;1 r q ~, t u r b 1 r; r; v € r s, T Y!l S E't a 1. (1 ~I l-; 4) h.:; Vt:. i n ~ r 0 (, II C C (1 the use 0 f
<br />rr;dintelpf!1ctry. lcrg~t: fish ilT1pll:ntH1 Hith Y"(;nio1rc;TTSr!itU'I~s (Ire f"1onitoreri
<br />on en establisliEd schedule, and dept.h, velocity, substrdtf type and
<br />tPnper?turl"'s are frIeasuret:'1 ~n(i ?SSt>SSf;r. at rE.-cular intc'rv(11s at tile location
<br />pinpoirtpo by a ra~io reCClver. Use of radiotelewttry ~ay be ~ore accurate
<br />th~t traditional fish collection means, but oossible mcditication ot fish
<br />b(~hovior, ccused by surgical implantiHion of a transmitter, cannot be
<br />esse:ssed. J\lso, tht: number of fish lfsed to rrprps/:nt hct.1tat choice is
<br />li!!'ite<1 by the: nUf11ber of relatively expE'nsiv~ ~nd short-lived
<br />racllot.rans)"littprs "vailthle. f0r ir:.r1.:'!nti'ltion. lJSI"' of rocdc.tE-1E'lTletry also
<br />restricts the size an~ thus the ace of tisb th~t c?n be implanted and
<br />Idonitcred. Usunlly only fhe- lfr~('r-.::M r.1C;fr fis\'1 can bp ir1plc:>ntp(. vJith
<br />r,-,rjio~r,]nSl7iitters Hitl' throrrtici'l battery lito ot 6 to lH rpcH!1:l1s.
<br />
<br />Another pClssibl(\ tiJS in r.hr; lFlt, l'l?S i')[pn rxplorrd by bC1ssr (l%2l.
<br />By using SCUI3A to obsf'r\'fI brewn and ridnb01,r1 tl~Clut in 1'1N';um to l2rge \-JE'~tern
<br />rivl'I"'S, he 1'1<'5 QrtrrIT'incd that fish oftc'n positior thffl1$clv('s clUSt' to bank
<br />or bottom strllcturf5, ~'/h(;'r(: \Vatf'r vploc;ty m€'y diffrr tror",averag€ water
<br />CClllllnn v\~locity, r.1€?'Sllrt:d at (l.b of tnr dC:'fnl". fro~ thp sur..fi1CE' in YJCiter less
<br />tllcW : teet deep, clno U.{ and O.~ of the drpUl in Wnte:r 0rl"iJf:cr th~n :; tE'et
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