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habitats preferred by the adult squawfish" (Miller et al. 1982). Our - general assessment of the San Juan River, Utah is that suitable habi- -_ tat for young squawfish (particularly YOY) is limited to the braided channel area (above RMI 78) of the river. Even within that area of ~ the river, steep gradients may limit backwater formation. As dis- charge drops, side channels may drain relatively quickly and be too short-lived to provide habitat for young squawfish. Twedt and Holden (1980) also found the San Juan "contains only minimal amounts of the shallow, low velocity backwaters thought to be necessary for the suc- cessful survival of young squawfish," but they also caution about the ~ limited scope of their study. At the flow level YOY fishes were sam- pled, backwater formation was basically restricted to the upper 59 miles of the study area. Assessment of the availability, suitability and changes in young squawfish habitat with changes in discharge need further study. Questions such as: Is habitat for young Colorado squawfish the primary factor limiting the population in the San Juan ~ River? and Is habitat manipulation possible to increase Colorado squawfish numbers in the San Juan River? may be answerable with further study. In general, shoreline habitat preferred by adult Colorado squaw- fish did not appear to be limited in the San Juan River, Utah. The ~ geomorphologic characteristics of the San Juan (e.g., high gradient, swift water velocities, unstable sand/cobble banks) create deep-water - areas along eroded banks in the braided channel area of the river, which should be available to adult squawfish. Slow water habitats, such as eddies, however, appeared to be somewhat limited from our - observations while electrofishing in spring and summer. Elsewhere in the Upper Colorado River Basin, radiotelemetered squawfish have been found predominantly in shoreline habitats with sand substrate and velocities averaging 0.2 m/sec (Green River), 0.1 m/sec (Yampa River), 0.5 m/sec (White River) and depths averaging 1.4 m {Green River), 0.9 m (Yampa River) and 0.7 m (White River). Relatively high water veloc- ities in shoreline habitats of the San Juan River may limit the use of ~ these habitats by Colorado squawfish. No velocity measurements were made during this study, but any future habitat suitability studies of the San Juan River should address this topic. During spawning, adult squawfish appear to have relatively speci- fic requirements for passage and spawning site selection. During run- ~ off, squawfish prefer velocities below those occupied at other times of year (Miller et al. 1982). Consideration should be given to the changes in habitat preferences of adults with changing seasons and flow conditions, although the dynamics of habitat preferences are only vaguely understood. Under present conditions and management strate- gies, populations of squawfish in some areas of the Upper Colorado ~ River Basin are declining (Miller et al. 1982). Little information on razorback sucker has been gathered in re- cent years, 1979-81, by researchers involved in systematic sampling of _ the Upper Basin (Miller et al. 1982). Relatively few razorbacks have - 42 - ,