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<br />It isdilflcultto predict the success lhal <br />Colorado pikeminnow might have in spawn- <br />ingur in establishing home ranges upstream <br />of the IS-mile reach Howe'..er, from what <br />wearrrentlyknowaooutthetem!X'ralurere_ <br />gJme oflhe ri\'er and the temperature re- <br />quirements of this speeies, thc Grand Valley <br />appears 10 be localed near the upStfeam <br />timilsoflhe optimal range for lhis popula- <br />lion Thus, the importance oflhe 15-mile <br />reach will nol bedimini~hedbythereestab- <br />lishmentofacceslltomOteu~1reamreachcs <br />Clearly, providing passage to reaches <br />upSlream nfPalisadeshould be Pllrsued as <br />part of recovery effnrts for the razorback <br />sucker and Colorado pikeminnow, Razor- <br />back !;ticker persisled in lhi~ reach unlil <br />r<<,em times suP-!:lesting thaI ils lhermal <br />requirements may be slighlly lower th,ln <br />those for Colorado pihminnow Alw, <br />raznrbacksuckertypicallycxploitwann,off_ <br />channel ponds and flooded areas This be- <br />haviOl mayservclootTsCltcmreraturelimi- <br />talions of the main channel allo\\o1ng the <br />ruorback sucker population to e~tcnd up. <br />stream farther than lhcpopulalion ofColo- <br />ra<.lopikcminnnw lIo"'cver.resloringpas- <br />sage is also amicipaled 10 e~lcnd the range <br />of year-round u1\eby Colorado pikeminnow <br />upSlream an estimated 14 mileS imu canyon <br />habital do\\onslream of De Beql.le Tbis "ill <br />I'ro\idea much-nce<.led addilion10 the lim- <br />iled amount ofa<.luh habilat currl.'l1llyavail- <br />abletolhispvpulation A1so,lhemoreup- <br />Slrt'am [)eHeque-lo-Riflere.lch, lhoughper- <br />haps 100 C(lOl for year-round use, mighl <br />serve Colorado pikeminnow as a sea~onal <br />fel.'ding area duringthewarmmonthsoflate <br />surnmcr(Osrnun<.lsonl99'la) However,this <br />moreul'Slream r...achshould nnl ,"evicwcd <br />as a subslilute for Ihe hillhquality habital <br />found wilhin the warmer, alluvial reaches of <br /> <br />ODlli j:J <br /> <br />lhcGrandValIey Nevel"lheless,alls<<lions <br />of former range in the upper Colorado <br />Riverareimportllnl and must be restored if <br />Ihe long-term viability ofthescendangcrcd <br />populalionsistobeassurcd <br /> <br />SUMMARY AND CONCLUSIONS <br /> <br />DUrlnglheoourseoflheir lives, indi- <br />vidualColoradopikcminnowmayutilizelhe <br />enlire I&S miles of the upper Colorado <br />Rivertomcetlhed...mandsofli'lcrrchanging <br />life hislOry needs lIabitalselcclionin- <br />vOlveslradeoffsbclwcenlherclalivelvail- <br />ability of van nus resources More optimum <br />thermal regimes for Colorado pikeminnow <br />andrlll.orbal:k sueker are located 10 lower <br />portionsofli'leriver, but subslfales arc <br />unsuitable for spawning and food availabil- <br />ity for adulls is low, Funher upstream, <br />sleepergradienlanrllocalgeolollicalcondi- <br />lions produce coarser suhWale and diverse <br />channel morphology resulling in suilahle <br />physicalcondilionsforspa"'ninll Ina<.l<.li- <br />tlOl\,grealcrnutrlenlinpulandlighlpene- <br />lralionresullsinsrcaterfoodproductionin <br />upslream reaches, particularly in alluvial <br />valleys Ilowcwr, for wann-waler sp~..::ies, <br />like Colorado pikeminnow and ruorback <br />sucker, lhefUl"lherUpslream an individual <br />ventures, the cooler the lhermal regime <br />becomes, and the more the p<ltenlial for <br />growth declines The grealesl cancenlra. <br />lions of adult Colorado pikeminnl,lw are <br />found in lhe Grand Valley, presumably <br />~uselhet>cnefilofhi8hfl,lodavajlability <br />outwci8hs lhe cost of a cooler Ihermal <br />regime Furtherupstream,foodavailability <br />remainshiShbut temperaluresdecline unlil <br />foodavailabi1ilycannolongerolfsellhe <br />negativeetlettsof1owtemperallnes Thus, <br /> <br />12 <br />