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COLORADO PIKEMINNOW <br />Information presented here regarding habitat use in the upper Colorado River <br />(Appendix Table H) is from Osmundson and Kaeding (1989) and on habitat preference from <br />Osmundson et al. (1995) and is based on results of year-round radiotelemetry of Colorado <br />pikeminnow in the Grand Valley during 1986-1989. Other life history attributes, as they <br />relate to the species' flow needs, were recently summarized by McAda (2001) and are <br />reviewed here where appropriate. <br />Adult Habitat Use <br />Winter <br />Between November and February, adult Colorado pikeminnow remain in localized <br />segments of river, primarily low-velocity habitats. Seventy-four percent of pikeminnow <br />locations had mid-column velocities <1.0 ft/sec. Pools and runs accounted for 77-95% of <br />all mesohabitats used during any given winter month; pools comprised 42-62%; runs, 27- <br />41%. All run habitat used was <2.0 ft/sec (slow runs). Eddies and backwaters were the <br />only other habitats used by Colorado pikeminnow in winter. Eddies were used only during <br />January and February and during that time accounted for 5-8% of fish locations; large <br />backwaters were used by some fish all winter accounting for 5-15% of fish locations. <br />Pools, backwaters and eddies were the preferred habitat types during winter in the 15-mile <br />reach (Fig. 2). <br />Spring <br />During spring, when water velocities are high and main-channel temperatures still- <br />relatively low, Colorado pikeminnow often seek out warm, off-channel, low- to zero- <br />velocity sites. Backwaters and flooded gravel pits together comprised 45% of pikeminnow <br />locations during April; 49% during May; 47% during June. Some use was also made of <br />eddies (2-9°x'0) and shorelines (3-8%). Use of riffles and rapids was negligible (1-2% during <br />12