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28 <br />at km 26.4 (mile 16.4), on the Yampa River. All endangered fish (adults <br />and larvae) sampled during this study are listed in Appendix C. <br />DISCUSSION <br />Migratory Movement <br />Five radiotagged fish of the sample population exhibited a highly <br />mobile migration of 200-350 km by migrating from the Upper Yampa <br />downstream to spawning areas in the lower 32 km of Yampa Canyon, and at <br />least four returned to the Upper Yampa near points of original capture. <br />Similar observations of migratory movement were documented by the USFWS <br />in 1981 (Miller et al. 1982a,b; Tyus et al. 1982a,b, 1983). <br />Timing of migration in 1981 and 1982 was similar with the major <br />movement into Yampa Canyon occurring in late June and early July. <br />However, water levels in 1982 were considerably higher than in 1981. <br />Peak flows in 1982 were approximately 15,000 cfs compared to 6,000 cfs <br />in 1981 (Miller et al., 1982b). Flows during migration into Yampa <br />Canyon were 7,000-10,000 cfs in 1982 compared to 1,000-2,000 cfs in <br />1981. These observations from two dramatically different water years <br />suggest that the timing of spawning migration of Colorado squawfish is <br />directly related not to flow levels alone but to other environmental <br />factors. Since squawfish evolved in a system of highly variable flow, <br />it is logical that they adapted to migrating and spawning at different <br />flow levels. Factors controlling timing of migration and spawning are <br />likely related to the annual flow cycle and temperatures to which fish <br />are exposed. <br />In 1981, all of the seven fish radiotagged on the Yampa River <br />migrated to the spawning area (Miller et al., 1982b). In 1982, three <br />fish in the radiotagged sample population did not appear to migrate.