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Tagging studies show that adult Colorado squawfish exhibit a migratory behavior during spawning season. Upstream spawning movement has been documented over a considerable distance, over 100 mi. Also, in the White and Yampa Rivers upstream and downstream movement occurs in association with spawning. There is evidence of homing behavior with some radio-tagged fish returning to areas where they were originally tagged following extensive migration. This homing behavior may be one explanation for frequent tag recoveries from the-same area over time. Upstream spawning movement and subsequent dispersion following a short spawning period was also noted in northern squawfish by Beamsderfer and Congleton (1981). Thus, Colorado squawfish behavior is similar to northern squawfish relative to spawning. Movement of adult Colorado squawfish appears to be related to flow, temperature and feeding. Adults were recorded further upstream, in the mainstem rivers and in tributaries such as the Yampa and White, during postrunoff than in prerunoff periods. The total movement picture suggests that adult squawfish move upstream during runoff and this movement, in part, is associated with spawning. There appears to be a general trend of upstream movement after runoff. Downstream movement occurs between postrunoff in the late fall and winter, and runoff the following spring- summer. Downstream movement is probably related to cold water temperature in the fall, inactivity and selection of deep-pool overwintering areas. Adults and juveniles exhibit flow-related habitat preferences by leaving main-channel habitats during peak runoff in favor of backwaters, tributary streams, side channels and irrigation-return streams. These lower velocity flow areas appear to be important during runoff as shelter from high velocities and also as feeding areas. The greater number of adult squawfish in the upper river reaches, both Colorado and Green Rivers, during the spawning, post-spawning period and the large numbers of YOY in Lower river reaches suggest spawning occurs to a large degree in the upper river reaches and rearing occurs in lower river reaches. From collections of larvae and YOY squawfish below suspected spawning site, we have concluded that there is a downstream drift of larvae and YOY following hatching. This movement can be any distance from a few miles (1-10 mi) to many miles (up to 100 mi). There is also evidence that, after their first year, juvenile fish move progressively upstream to areas of better feeding including lower sections of tributary streams. Observations of YOY and juvenile squawfish in backwaters suggest different movement by the two ages of fish. YOY moved between shoreline runs and backwaters apparently preferring the warmer daytime water temperature; they moved into backwaters in late morning and returned to the main channel at night. Juveniles seemed to move out of backwaters in the morning and into backwaters in the evening. Both adults and juveniles were more active in shallow water at dawn and dusk indicating a probable twilight feeding activity. !S