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of these rivers have many good backwaterss the larvae probably find the best available habitat and drift downstream looking for better habitat. As squawfish become larger. (150-200 11111) their numbers in the catch of researchers drops dramatically (Holden 1977s Holden and Selby 1979). This same phenomenon was noted for juvenile suckers by McAda (1977). It appears that this is the size where these fish begin using the main river channelss hence they become much more difficult to sample. Food habits would also suggest a change, from eating insects and crustaceanss most common in such backwater areas, to fish that are found in a larger variety of habitats. The ability of the juveniles to manuever in the main channels is probably also enhanced after it attains about 200 rnm in length. Adult habitat preferences have been shown to change with season, as well as with the habitat available. Twedt and Holden (1980) summarized much of the available data and categorized habitat preferences for substrates depth, velocitys and cover for pre-runoff, runoffs and post- runoff periods (Figure 3s 4s and 5). These data indicate that adults prefer run type habitat along shore of medium depth during pre- and post-runoff periodss but prefer backwaters during high flow periodss although runs are also used during this time. This same general pattern was noted in the Yampa River in 1981. Adult squawfish were found in edd i es and near mouths of i rri gat i on returns s as we 11 as the shore 1 i ne of runs during prerunoffs sought out large backwaters during runoff and utilized deep holes and diverse habitats in post-runoff periods. Additional habitat preference curves have been constructed by the Cooperative Instream Flow Service Group (no date)s and are in general agreement with those shown here. 8