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develop as spring flows decline. Such habitat is generally associated with lower gradient reaches. Tyus (1991b) also found that young Colorado squawfish exhibited a diel pattern of backwater use that was positively related to backwater temperature. Most of the 1,194 young Colorado squawfish were captured in spring when water temperature in backwaters equalled or exceeded main channel temperature. Marked young were highly mobile and moved between several habitat types during a 24-hour period. Juvenile and Adult Habitat Adult Colorado squawfish are large-river fish found in a variety of depths and velocities over silt, sand, gravel, and boulder substrates (Holden 1973; Wick et al. 1979, 1981; Holden and Twedt 1980; Holden and Wick 1982; Miller et al. 1982a, 1982b; Tyus et al. 1982a, 1984; Valdez et al. 1982b). Adults and juveniles use various habitats depending upon season, streamflow, water temperature, and availability (Holden and Wick 1982; Wick et al. 1983, 1985, 1986; Tyus and McAda 1984; Tyus 1990). During peak runoff, fish move into backwater areas or flooded riparian areas where velocity is lower and water temperatures are higher than in the main channel (Wick et al. 1983). Adult Colorado squawfish exhibited little movement during winter (October-April) in the upper Green River (Valdez and Masslich 1989). Of 20 adults radio-tagged in October, 15 moved less than 3 miles by the end of the following March. The fish occupied primarily slow runs, slackwater, eddies, and backwaters. During winter, adult Colorado squawfish in the Yampa River use backwaters, runs, and eddies, but are most common in shallow, ice-covered shoreline areas (Wick and Hawkins 1989). In spring and early summer, adult squawfish utilized shorelines and lowlands that were inundated during typical spring flooding, and this natural lowland inundation was viewed as important for their general health and reproductive conditioning (Tyus 1990). Use of these habitats may mitigate some of the effects of winter stress and aid in offsetting a large energy expenditure required for migration and spawning. MOVEMENT/MIGRATION Migration is an important component in the reproductive cycle of Colorado squawfish, and Tyus (1990) reported that migration clues, such as high spring flows, increasing river temperatures, and possible chemical inputs from flooded lands and springs, were important to successful reproduction. Radiotelemetry studies and collections of spawning fish have added to the knowledge of Colorado squawfish spawning activities, seasonal movements, and habitat use (Tyus et al. 1982b; Radant et al. 1983; Wick et al. 1983; Tyus and McAda 1984; Archer et al. 1985; Tyus 1990; McAda and Kaeding 1991). During the spawning season, adult Colorado squawfish migrate upstream and downstream to reach spawning areas in the Green River Basin and movements of 200 miles have been reported (Miller et al. 1983; Tyus 1985; Tyus 1990). Fidelity to spawning locations have been observed for Colorado 23