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RESULTS AND DISCUSSION Colorado Squawfish Spawning Investigations over the past six years by a number of investigators in the UCRB have illustrated that spawning behavior of Colorado squawfish is both complex and highly variable. Major migrations to specific spawning areas observed in the Green and Yampa Rivers have not been as evident in the Colorado. Two areas in the Green and Yampa Rivers are well documented through repetitive observations of several indicators but several other spawning areas are believed to exist in the Green and Colorado Rivers though their location has not yet been well defined. Prespawning migrations Extensive spawning migrations have been consistently observed during the past five years in the Green and Yampa Rivers through radiotelemetry and recapture of tagged fish. This behavior has not been as evident in the Colorado River where a shorter period of research has been carried out and radio tracking has been less successful. The reasons for these divergencies are not clear but circumstances may differ enough to elicit differences in behavior between the two systems. It is clear that Colorado squawfish do have specific spawning habitat requirements and that they do migrate whatever distance is necessary to locate and utilize those habitats. Radiotracking and tag returns have demonstrated extensive migrations to and from the spawning area in the Yampa and Gray Canyon on the lower Green (Figure 1) but this has not been the case in the mainstem Colorado River above Lake Powell (Figure 2). In the Green and Yampa Rivers movement towards the spawning areas of radio-tagged fish has commenced in early June except in 1981 when May and June flows were only about 38% of average and significantly different fluvial condi tions occurred. In the Colorado River movement increased during the spawning period but no concerted movement to common areas was observed. Tracking success was very good in the Green and Yampa systems with 50% of the fish being tracked through the spawning period. Main- taining contact with radio-tagged Colorado squawfish was more difficult 10