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<br />DOilJ FT CDlL~~JS <br /> <br />TEL:303-490-2621 <br /> <br />Apr 28 93 <br /> <br />13:18 No.OOe P.34 <br /> <br />. <br /> <br />. <br /> <br />Talk 2: To determine annually from 1992 to 1996 the retention of <br />Colo~ado squawfish larvae wichin the upper mainstem Colorado River based <br />on comparison of larval drift density peaks at sample aitas, <br />availability of nursery habitat, the relative 10.. of larvae downstrea~ <br />due to larval drift or the loss of juveniles duo to displacement during <br />high spring flows; relate to annual flow variable. in both rivers. <br /> <br />Estimatos of relative abundance or annual production of Colorado <br />squawfish larvas from the drift-net .ampling at stations will bc <br />compared among stations to determine downstream displacement. Trends in <br />numbers of larvae captured and estiMated population from drift-uat <br />.ampling will be compared with trends in numbers and catch rates of <br />larvae or young-of-the.yesr Colorado squawfi.h csptured in nursery <br />backwater habitat within tha atudy resch during standardized monitoring <br />to determine the degraa of retention of Colorado aquewfish larvae within <br />the reach. Trends will be compared to habitat availability and <br />nonnative fi.he. abundance. <br /> <br />Task 3. To daurllino from 1992-1996, the ereecC of experimental. flow <br />manipulacion and length of growins season upon size of Colorado <br />aquawfish young-of-tho-yaar in the fall as it relate. to potential <br />overwinter survival. <br /> <br />Si%e of Colorado aquawfiah young-of-year vil1 be measured at all <br />ph.ae. (larval drift stage, nursery backwaters in September) to <br />eatablish growth rate and size prior to overwintering. Calculation of <br />growing seaaon will ba conducted at sevorsl temperature thresholds to <br />e.ti.ate number of degree days In the season. Change. In fish growth <br />rate, size at the and of ths srovins aeason snd length of the gro.ins <br />season vill be compared to flow regi.e parameter. affected by the <br />Colorado and Gunnison rivers, and experimental releases from Aspinall <br />re.arvoirs to a.ses. relationships between the.. variables and potential <br />prodictive regres.ion models. Potential fitness of each ye.r cla~s for <br />overwinter survival vill be as.es.ed using data and conclusions in <br />Thompson (1989). <br /> <br />VI. Task Description (FY-1994) <br /> See V. above. <br />Vll. Study Schedule <br /> Tasles 1-3: Start: FY 1992 <br /> End: FY 1997 <br />VIII. A. FY 1994 Work: <br /> <br />Description: <br /> <br />Tasks 1-3: larval drift sampling. lO-day sample <br />In July, 4 aites. Acquire relevant data from <br />nursery habitst study and atandardized fall <br />sainins in study reach for comparisons. <br /> <br />3 <br />