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DRAFT moortance of Tributaries Tributaries of the Green and Colorado rivers may be especially important to the continued survival of the Colorado squawfish. Colorado squawfish historically or presently occupy tributaries of. the Green and Colorado rivers,. including the Yampa, Ouchesne, White, Gunnison, Dolores, and San Juan rivers in the Upper Basin, the Gila River and its tributaries, the Salt, Verde, and other rivers in the Lower Basin. Tagging and telemetry studies indicate the Colorado squawfish moves long distances from spawning areas in the mainstem Green River to feeding and overwintering areas in the Yampa, White, and Duchesne rivers (Miller et al. 1982x, 1982b, 1983; Radant et al. 1983; Tyus et al. 1982x, 1982b, 1987). Tyus (1986) suggested that tributaries play an important role in the life history strategy of the Colorado squawfish and perhaps serve to reduce intraspecific competition. Miller et al. (1982x) reported a net movement of juveniles from the Green River to the White River, while Radant et al. (1983) documented movement of adult fish between the White-and Green rivers and Green and Yampa rivers during the spawning season. There also is a downstream movement of larva l Colorado squawfish from the Yampa River to the Green River (Haynes et,al. 1984; Miller et al. 1982b; Tyus et al. 1982b). Furthermore, a net upstream movement of adult and juvenile Colorado squawfish from the Green River into the Yampa-River has been suggested by Miller et al. (1982b) and Tyus (1986). Colorado squawfish larvae were collected from the Yampa River within Dinosaur National Monument each year during :the period 1980-83 (Miller et al. 1984; Wick et al. 1981), and spawning migrations into the lower Yampa were observed in 1981 (Miller et al. 1982b; Tyus et al. 1982b), 1982 (Wick et al. 1983), 1983 (Archer et al. 1985; Tyus 1985), and 1984-85 (Tyus et al. 1987). Holden (1980) indicated that flows from the Yampa River were important to the reproductive success of Colorado squawfish in downstream areas of the Green River. He noted that, in 1977 (a dry year), young-of-the-year Colorado squawfish were not collected in nursery areas below Jensen, Utah, although they had been collected in these areas during the more "normal" water years of 1975, 1916, 1978, and 1979. Analysis of the hydrographs for these years indicated that the Yampa River was the primary contributor of high spring flows, which generally exceeded 12,000 cfs and approached 20,000 cfs at the Jensen gage. The exception was 1977, a year of low flow in the Yampa River. Spring flows recorded-that year at Jensen did not exceed 8,000 cfs. The data suggested the importance of the quantity and timing of flows from the Yampa River to the success of the Colorado squawfish in the Green River system. Holden (1980) concluded that the Yampa River and other major tributaries were maintaining the Green River as one of the last potential habitats for the Colorado squawfish. 14