8144

• UCREFRP Catalog Number: 8144
• Author: Valdez, R. A.
• Title: Evaluation of Habitat Utilization Curves for Endangered Colorado River Fishes.
• USFW Year: 1985.
• USFW - Doc Type: \
• Copyright Material: NO

.., ^ i'

3-6

diffl"rence exists between the data of the two areas. This should be done
before pooling the data.

2. Assumpti on ;j (page 35), assumpti on 2 (pagE' 37) and assumpti on 2
(page 39) may not be accep'tablc because of tnr: inht::re:nt geomorphological
di ffercnces in the three ri vers ~ Depth, vel oci ty and substrate preferences
in 'the GreE:n ana Yampa Rivers may not be simil ar to those of the Colorado
R i v e r . Un for tun ate 1 y t his may be a,n e s sum p t i on t hat wi 11 h a v e to be
accepted because of the few numbers of humpback chubi" the Green and Yampa
Rivers.

3.2.Y Colorado s(1ui~Vlfish '10Y, juvenile and
rreterencf (sic. utilization) curve.

adult

temperature

1. kt h'ilst one of thE' thrE:F. 1 ife stugE:S (YOY) has a demonstrably
(Ii ffl'rpnt t~nrerctl.lr(' prt:ferrncf:. YOY SCUiiHfi sh ?rE: consi stE'rtly found in
shal1u\'J VJater hi"bitats such uS backwc!p.rs; areas that arrc .genf'ral1y warmer
than deeper milin channel hebit2ts occupil'd by aClllts. Juveniles appCi)r to
use backweters Jt nicht (warm waters) and main ch<'\nnel h2bitots in the
caytinp (cool er \'/ater )v. There arE: prcbab ly thrpe ai st i net hut overl app; ng
te~perRturp preference curves th~t can be develop~~ for Colorado s~uawfish.

2. It is unclear ?S to how thE tfmpereturc preterercp curve was
fOrP:ulc;ted fror.i cot,;, generated by f:le("y. (1ge2). l,ctue1ly, the work at UtClh
S:t1tE: University \:as ccr.ducted joirtly Dy R. V. Gun,ley, C. h.. Berry, R.
Pinent"l ana 1. black (19b2). USin9 ttH'~'e aCi,li~ation t~:r.lppr<?tures (14, 20,
,,(oC i, only juveni 1 e ana aaul t squa~lfi sh wen' tested. t.cutf- preferenCE of
juv~nilcs (24.6oC) end adults (21.5 - 25.70Cl ac(li~atEd to oifferent
tE'-flp(;:rr:tun:s ~:f.;n: riot signiticantly diffErent, altrcllgh there 'tJere
sigrdficant Clifft:rencEs I,'/ithin tile juvenile S'roup, incica..ing v wider
~rEference by juV':'niles. Acuteprt:'fcrcrocE:S of aaults WuS net S;~Hlif;cant
b(~causr:= of "sr'cil SClnple sizes anc: higrif'r vClriilbility ./iUoin each
;~cc1im,;t;c.n terr:pE:r?1.urE:." Using tli;:se laboy',nory rXp,;,r;(\IH,tS t.o gpncrilt.e a
tE:'li1peratllr€ preferH,ce curvE' is qupstioncbh: because ot sr.:fil sample size,
absencf.; of youllr-of-tN~-year anri 1 iH'oe aoul ts as sample slIbje::ctS, and the
possible influence cf othf'r \'Jater quality fi'lctors. Fielo recorded
tt:li!pc:r<1turES shoul d be corpared ant used to hel p generatE' pretercnc1a and
SUPfl1er.1Cnted by laboratory experiments t.o prOVidE: rang~s and extreP1E's.

3.2.1U Aoult Coloraao SQu?wfish prespawning migration ana spawnin~
temperaturc utlllzatlon curves.

1. Temperature experimf~nts on Co10r3do squawti sh i'/ere conducted by R.
v. PuH:lp.y, C. R. BErry, R. PimentAl end T. Black (l~Jb2) at Utilh State
Univcrsity (D~te Utilized, item 3, pi'l(!(' 4;). TllC "critical thpr!!1nl rnaximau
of 350C was a te:,mpE-rnttJre uspd to test hatchnbil ity anci survivl!bi 1 ity of
eggs. No Pggs h;~tcr.f:(t at this H'lilpfl"eturE'. It is not Known if this is the
critical thcrrn8l ~nxim~ for adults, but probebly ~rprox;~et(s 2 trup value.

2. Use of USG~ strp8,mgc/ugp inforr'ation ;s i.l rp(!scntble WiJ.y of
determining prcspawning and migration temperatures. On-site spawning
te:mperaTun:s (pa~c 47) cr~ probJb1y the bt'st "I(;asurr~ i'vail~blc:. It is
intcrpsting to compJrc the ~l v~lur with spawninp t~~p(~aturc seen in
hatchC'Y';es. Hamman (lE'c:2) obst,:rv('d tile first signs at rlcturi'ltion in males