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..~ <br />squawfish following hatching. Extensive studies in the Yampa and upper Green <br />Rivers have demonstrated downstream distribution of young Colorado squawfish <br />from known spawning areas (Archer et al. 1986; Naynes et al. 1985). Miller <br />et al. (1982) also found that young-of-year Colorado squawfish, from late <br />summer through fall, preferred natural backwater areas of zero velocity and <br />less than 1.5-foot depth over a silt substrate. Juvenile Colorado squawfish <br />habitat preferences are similar to that of young-of-year fish, but they appear <br />to be mobile and more tolerant of lotic conditions away from the sheltered <br />backwater environment. <br />Information on radio-tagged adult Colorado squawfish during fall suggests that <br />fish seek out deepwater areas in the Colorado River (Miller et al. 1982), as <br />do many other riverine species. River pools, runs, and other deep water <br />areas, especially in upstream reaches, are important winter habitats for <br />Colorado squawfish. <br />Very little information is available on the influence of turbidity on the <br />endangered Colorado River fishes. It is assumed, however, that turbidity is <br />important, particularly as it affects the interaction between introduced <br />fishes and the endemic Colorado River fishes. Because these endemic fishes <br />have evolved under natural conditions of high turbidity, it is concluded that <br />the retention of these highly turbid conditions is an important factor for <br />these endangered fishes. Reduction of turbidity may enable introduced species <br />to gain a competitive edge which could further contribute to the decline of <br />the endangered Colorado River fishes. <br />Migration <br />Radio-telemetry studies show upstream and downstream movement of adult <br />Colorado squawfish in the main stem Colorado River. The most dramatic <br />movement was exhibited by a fish implanted with a radio transmitter at Gypsum <br />Canyon in upper Lake Powell on April 5, 1982. The fish was contacted next in <br />the lower Cataract Canyon area on July 9, 1982. The next contact was made <br />above the Black Rocks area of Ruby Canyon, some 160 miles upstream. The <br />movement was accomplished in 41 days and is believed to be related to <br />spawning. At the end of September 1982, this fish was located in the Colorado <br />River in the vicinity of Clifton, Colorado (river mile 178), nearly 200 river <br />miles from its furthest documented downstream location. <br />Other radio-tagged fish in the Colorado River have not displayed such dramatic <br />migratory behavior. Radio-telemetry studies conducted by the Colorado River <br />Fishery Project (Fishery Project) from 1982-1989 (Miller et al. 1982; <br />Archer et al. 1986; Osmundson and Kaeding 1989), which focused on upstream <br />reaches of the Colorado River in and around the Grand Valley, provide the best <br />indication of use of the 15-mile reach above the confluence of the Gunnison <br />River at one time or another during the field season. Movement of these fish <br />during afield season was generally limited to 25-30 miles. <br />During 1986-1988, the Fishery Project radio telemetered 17 adult Colorado <br />squawfish collected from the 15-mile reach above the Gunnison River in June <br />(Osmundson and Kaeding 1989). The fish exhibited a diversity of localized <br />movement throughout the Grand Valley but spent a major part of time in the <br />