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~ . ~~ N r 21 c to be mobile and more tolerant of lotic conditions away from the sheltered backwater environment. Larval Colorado squawfish have been collected in the Gunnison River upstream and downstream of the Redlands Diversion Dam. Burdick (1997) reports that the capture of larval Colorado squawfish in 1995 and 1996 upstream of the. Redlands Diversion Dam indicates spawning is occurring upstream of the dam. Information on radio-tagged adult Colorado squawfish during fall suggests that fish seek out deep water areas in the Colorado River (Miller et al. 1982). as do many other riverine species. River pools. runs. and other deep water areas. especially in upstream reaches. are important winter habitats for Colorado squawfish (Valdez and Masslich 1989. Wick and Hawkins 1989). Very little information is available on the influence of turbidity on the endangered Colorado River fishes. It is assumed, however, that turbidity is important. particularly as it affects the interaction between introduced fishes and the endemic Colorado River fishes. Because these endemic fishes have evolved under natural conditions of high turbidity. 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. Razorback Sucker The razorback sucker is a Colorado River Basin endemic species and was historically abundant and widely distributed within warm water reaches throughout the Basin. Historically. razorback suckers were found in the mainstem Colorado River and major tributaries in Arizona. California. Colorado. Nevada. New Mexico. Utah. Wyoming, and in Mexico (Ellis 1914. Minckley 1983). Bestgen (1990) reported that this species was once.so numerous that it was commonly used as food by early settlers and. further. that commercially marketable quantities were caught in Arizona as recently as 1949. In the Upper 8asin. razorback suckers were reported in the Green River and were very abundant near Green River. Utah. in the late 1800's (Jordan 1891). An account in Osmundson and Kaeding (1989) reported that residents living along the Colorado River near Clifton. Colorado. observed several thousand razorback suckers during spring runoff in the 1930's and early 1940's. In the San Juan River drainage. Platania and Young (1989) relayed historical accounts of razorback suckers ascending the Animas River to Durango. Colorado. around the turn of the century.