2013-04-05_PERMIT FILE - C1996083A (24)

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• River pools, runs, and other deep water azeas, especially in upstream reaches, are important winter habitats for Colorado pikeminnow. Very little information is available on the influence of turbidity on the endangered Colorado River fishes. It is assumed, however, that turbidity is important, particulazly as it affects the interaction between introduced fishes and the endemic Colorado River fishes. Because these endemic fishes have evolved under natural conditions of hish turbidiri, it is concluded that the retention of these highly turbid conditions is an important factor for these endangered fishes. Reduction of turbidity may enable introduced species to gain a competitive edge which could further contribute to the decline of the endangered Colorado River fishes. Migration Radio-telemetry studies show upstream and downstream movement of adult Colorado pikeminnow in the main stem Colorado River. The most dramatic movement was exhibited by a fish implanted with a radio transmitter at Gypsum Canyon in upper Lake Powell on Apri15, 1982. The fish was contacted next in the lower Cataract Canyon azea on July 9, 1982. The next contact was made above the Black Rocks azea of Ruby Canyon, some 160 miles upstream. The movement was accomplished in 41 days and is believed to be related to spawning. At the end of • September 1982, this fish was located in the Colorado River in the vicinity of Clifton, Colorado (river mile 178), neazly 200 river miles from its furthest documented downstream location. Other radio-tagged fish in the Colorado River have not displayed such dramatic migratory behavior. Radio-telemetry studies conducted by the Colorado River Fishery Project from 1982-1989 (Miller et al. 1982; Archer et al. 1986; Osmundson and Kaeding 1989), which focused on upstream reaches of the Colorado River in and azound the Grand Valley, provide the best indication of use of the 15-mile reach above the confluence of the Gunnison River at one time or another during the field season. Movement of these fish during a field season was generally limited to 25-30 miles. During 1986-1988, the Fishery Project radio telemetered 17 adult Colorado pikeminnow collected from the 15-mile reach above the Gunnison River in June (Osmundson and Kaeding 1989). The fish exhibited a diversity of localized movement throughout the Grand Valley but spent a major part of time in the 15-mile reach. Two remained in the reach throughout the estimated spawning period. Snawnina Activiri A suspected prespawning aggregation of adult Colorado pikeminno~v was observed by Fishery `rr~ject personnel at river mile 1i83 in the 1~-mile reach above the Gunnison River confluence • sn mid-July 19&2. In the first observation, three radio-tagged fsh ia~ere rraekect to one riverire pool area, and nine adults at or near spawning condition were then captured there afrer limited net sampling efforts. The aggregation occurred a few days afrer mean daily water temperature