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3) Determine if fish movements in winter are related to fluctuating releases from <br />Flaming Gorge Dam. <br />4) Evaluate the assumptions of overwinter survival estimates and specifically determine <br />how Colorado pikeminnow movements affect these estimates. <br />5) Evaluate alternative methods for collecting age-0 Colorado pikeminnow in <br />backwater, embayment, eddy, and main-channel shoreline habitats during the winter. <br />Over the three year period of this study, a total of 732 young Colorado pikeminnow were <br />captured, 404 were marked and released (fish captured on the last pass during spring sampling <br />were not marked), and 38 fish were recaptured. Population estimates were made that averaged <br />26 fish per river mile, with coefficients of variation (CV) that ranged between 0.25 and 0.59. <br />The imprecision of our estimates was the direct result of not catching enough marked fish. <br />Unfortunately, during the three years of this study, age-0 Colorado pikeminnow were only one- <br />tenth as abundant as the average for the previous 13 years. As a result of the imprecision of the <br />population estimates, we were unable to make overwinter survival estimates. <br />Age-0 fish marked in autumn and recaptured the following spring generally moved less <br />than 10 miles downstream after being at large for 170 to 200 d. This result is consistent with <br />other studies and gives us confidence that rate of movement between autumn and spring will not <br />bias estimates of overwinter survival for a 40-mile reach, but it could be a problem for reaches <br />less than 40 miles. <br />A number of techniques were attempted to sample for young Colorado pikeminnow <br />under the ice that included seining, minnow traps, clover traps, fyke nets, and an underwater <br />camera. The most effective approach was the use of an underwater camera and video cassette <br />A-ix