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<br />squawfish to an endangered status (Seethaler 1978, Holden and Wick 1982). <br />We evaluated the effects of present annual flow regimes during summer and <br />early autumn relative to larval hatching, distribution, habitat use, and <br />growth. We sampled standing crops of young Colorado squawfish in autumn <br />and spring to evaluate the effects of harsh winter conditions on survival <br />and growth. Finally, we evaluated summer conditions and the sizes (TL) of <br />age-0 Colorado squawfish in the upper and lower Green River with the <br />hypothesis that growth of age-0 Colorado squawfish to a larger size would <br />be attained as downstream distance from Flaming Gorge Dam increased. <br />Study Area <br />The Green River basin is located in eastern Utah, northwestern Colorado <br />and southern Wyoming (Figure 1). The primary study area included the <br />lower 552 km of the mainstream Green River downstream of its confluence <br />with the Yampa River, and the lower 30 km of the Yampa River during 1979- <br />1988. However, sampling was also conducted in the Green River upstream <br />from its junction with the Yampa River in 1979-81 and in the lower 225 km <br />of the White River in 1981. The Green River was divided into seven strata <br />(A-G in Figure 1) between river kilometers (RK) 35-552. Strata A, 6, E <br />and F are characterized as low gradient (0.2-0.4 m/km) reaches with sand <br />and silt substrates. Strata C, D and G are relatively high gradient <br />reaches (1.3-2.1 m/km) dominated by boulder and cobble substrates. <br />Methods <br />Larval collections.-Hatching dates, growth and distribution of larval <br />Colorado squawfish (< 25 mm total length, TL) in the Green and Yampa <br />rivers, 1981-1988, were determined by collections with seines and drift <br />nets. Larval seining was conducted in the Green, Yampa, and White Rivers <br />4 <br />