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contact was lost with most fish by the between Palisade and Westwater continu was made below Westwater in September. the end of their expected battery life however, the possibility that the fish ruled out. end of August, intensive searches ad through November; one search The radio transmitters were near about the time contact was lost; left the study area cannot be Movement of radio-equipped Colorado squawfish was closely monitored during the spawning period in an attempt to locate spawning areas. On July 13 three radio-tagged fish were found in a small pool in a side channel at RM 178.3 near Clifton, Colorado. Trammel nets drifted through the pool collected nine Colorado squawfish including one radio-tagged fish; five of these fish were ripe males. The remaining fish were tuberculated in a pattern believed typical of mature females, but sex products could not be produced when pressure was applied to the abdomen. An additional radio-equipped Colorado squawfish was subsequently observed in the vicinity of this pool. A large eddy at RM 176 was independently visited by five radio- telemetered Colorado squawfish during the subsequent two weeks. A ripe male Colorado squawfish was collected from this location. A radio- tagged Colorado squawfish recaptured from a nearby side channel had a distended abdomen and had gained about 500g in the six weeks since it was released. Although sex products were not expressed from this fish, it was most likely a maturing female. Although an aggregation of ripe males is a significant observation, it does not necessarily indicate that spawning occurred in the immediate vicinity. Males of most minnows ripen earlier than females, and they can move considerable distances after ripening before spawning occurs (Breder and Rosen 1966). We encountered ripe males in WWWA (RM 163.6) one month before the aggregation at RM 178.3 was noted. We equipped two of these fish with radios; one radiotagged fish was subsequently found among the group of radiotelemetered fish that constituted the aggregation described above. One of these fish moved 10 miles, and the other 15 miles, during the time they were ripe. Although spawning did not necessarily occur in the immediate vicinity of RM 176.0 or 178.3, it did occur in the Grand Junction area as demonstrated by the collection of larval Colorado squawfish in August. The aggregation of mature Colorado squawfish near Clifton, Colorado occurred when river flows were receding and water temperatures were near 20 C (Figure 12). In addition to the radio tracking effort in the Grand Junction area the FWS also conducted similar radio tracking work in the Green River. Green River work was a continuation of the previous 2 years radiotelemetry • to further define movement and spawning for Colorado squawfish. Eleven adult Colorado squawfish were radio-tagged and tracked by FWS in the Green River during 1982. Collection of adult fish for tagging began on May 4th and by May 20th eleven fish ranging in size from 522 to 810 mm -20-