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DRAFT (tuberculated) (Tyus et al. 1987). Four fish tagged in the White River have been recaptured at the Yampa and Gray canyons spawning areas, and the recapture of five fish tagged and recaptured in the Yampa River spawning grounds after 2 or more years indicate a fidelity to that area (Tyus 1985, Tyus and Karp 1989). It is possible that the Yampa spawning aggregation is historical; Holden and Stalnaker (1915b) reported increased numbers of ripe ,Colorado squawfish in the lower Yampa River in July 1968-70, and Seethaler (1978) reported ripe fish there in 1974-75. Successful reproduction was substantiated when larval Colorado squawfish (9 to 13 mm [.35-.51 in] TL) were taken below river kilometer (RK) 32 (RM 20) on the Yampa and downstream Green River in 1980, 1981, and 1982, and below RK 40 (RM 25) in 1983; however, only one has been collected upstream from these points (Haynes et al. 1984; Tyus et al. 1987). Gray Canyon of the Green River was suspected as a spawning site in 1981 when a radio-implanted squawfish from the White River was._tracked to that location (Radant et al. 1983; Tyus et al. 1982a). Spawning was confirmed there in 1983 (Tyus 1985). Additional Colorado squawfish have been tracked to Gray Canyon, and 57 ripe fish were collected there in 1981-85 (Tyus et~al. 1987). Radiotelemetry studies show upstream and downstream movement of adult Colorado squawfish in the upper mainstem Colorado River. One dramatic example was provided by a fish radio tagged in Gypsum Canyon of upper Lake Powell on April 5, 1982. On July 9,-1982, the fish was located in the lower Cataract Canyon area. The next contact was made above the Black Rocks area of the Colorado River some 258 km (161.25 miles) upstream. This movement was accomplished in 41 days and was believed related to spawning. At the end of September, the fish was located in the Colorado River near Clifton, Colorado, approximately 320 km (200 miles) from-its furthest documented downstream location. However, not all radio-tagged fish in the mainstem Colorado River have displayed such dramatic migratory behavior. Radiotelemetry studies conducted by the Colorado River Fishery Project from 1982-85 (Archer et al. 1985; Miller et al. 1983) in the Grand Valley region of the Colorado River found that movement during April-October was generally limited to 40-48 km (25-30 miles). , Two reaches of the Colorado River containing suspected spawning areas are Black Rocks to Loma (RK 217-233 [RM 135-145]} and Grand Junction to Clifton (RK 251-290 [RM 160-181]) (Archer et al. 1985). .Location of larval squawfish -aggregations and the presence of suitable spawning habitat in the Colorado River near Cataract Canyon 22-29 km (14-18 miles) below the confluence of the Green, in Professor Valley at above the confluence of the Green at RK 121-137 (RM 75-85), and upstream from the Dolores River confluence at RK 160-185 (RM 100-115) indicate spawning is occurring in or near these areas as well (Archer et al. 1985; Valdez and Williams 1985, 1986). 10