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SUMMARY <br />Twelve Colorado squawfish were surgically implanted with radio- <br />transmitters on the Upper Yampa River between river kilometer (km) 86 <br />and 172 in March and April, 1982. Five fish exhibited highly mobile <br />migrations of 200-350 km by migrating from the Upper Yampa downstream to <br />spawning areas in the lower 32 km of Yampa Canyon, with at least four <br />returning to the Upper Yampa near points of original capture. The major <br />movement into Yampa Canyon occurred in late June and early July. Three <br />fish of the sample population did not migrate. Radio contact was lost <br />with three other fish in June and July. <br />A chute channel with rubble gravel substrate at river km 26.4 was <br />the only site at which squawfish were observed by radiotelemetry to <br />exhibit spawning behavior. Aggregations of ripe fish captured with nets <br />at several locations throughout the lower 32 km of Yampa Canyon suggest <br />spawning at other sites. The river within the spawning area is <br />characterized by large meandering bends, unique pool-riffle-pool <br />sequences, and large braided rubble (cobble) bars. <br />From July 2 through August 7, 40 Colorado squawfish were captured <br />between river km 33 and km 8.2. Additional pre- and postspawning <br />samples resulted in the capture of 30 squawfish. Ten fish were <br />recaptured during the sampling season. Capture/recapture information <br />supplemented radiotelemetry data to show that (1) fish from the Yampa, <br />White, and Green rivers use the Yampa Canyon spawning area then return <br />to their resident home ranges; (2) recruitment of adult Colorado <br />squawfish into the Upper Yampa River likely originates from nursery <br />. v