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1 <br />1 <br />1 <br /> <br /> <br />1 <br /> <br /> <br />1 <br />1 <br />1 <br /> <br /> <br />surveys and field reconnaissance, in an effort to identify fish habitat. <br />Detailed descriptions of these strata are provided in Miller et al. (1982). <br />Habitat use data for all fish species (e. g., major habitat type, depth, <br />velocity, and substrate information) was collected by FWS and CDOW in 1981. <br />Migration patterns and habitat use of Colorado squawfish were investigated <br />usin; radiotracking methods from 1981-1985. Spawning behavior of Colorado <br />squawfish in the Yampa River has been studied 1981-1987 (Tyus et al. 1987, <br />Wick et al. 1983). Studies of general habitat use by humpback chub and <br />winter habitat use by Colorado squawfish were initiated in the Yampa River in <br />1985. These studies are being continued in 1988 by FWS (Vernal, UT) and the <br />Larval Fish Lab (Colorado State University, Fort Collins, CO). <br />Colorado squawfish <br />Adults: Adult Colorado squawfish are distributed in the Yampa River from its <br />mouth upstream to Craig, Colorado. Catch records from standardized sampling <br />programs indicated adults were concentrated in strata 4-8 (Figure 3) during <br />the non-breeding period (Miller et al. 1982, Wick et al. 1985). In 1981, <br />catch of adult Colorado squawfish averaged 0.04 fish per hour below, and 0.3 <br />fish per hour above the confluence of the Little Snake River (Miller et al. <br />1982). <br />Adult Colorado squawfish occupied a variety of habitats but were most <br />commonly found in eddies, pools, runs, and shoreline backwaters, over sand and <br />silt substrates (Figure 4). Visual observations in shallow water indicated <br />that adults use sheltered microhabitats behind boulders, flooded vegetation, <br />or other cover. During the summer months, radiotagged fish were most often <br />located in eddies in deeper water, where movements suggested heavy use of <br />7 <br />