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fishes were captured. A summary of the geographical distribution of the endangered fishes with physical descriptions of the strata sampled is given in the Appendix. However, study results may not be directly comparable, because the different ~ geographic areas may have been sampled by different protocols and in different seasons or years. Colorado pikeminnow ~ The Colorado pikeminnow is now restricted to the UCRB and persists in only four populations, which are located in the Yampa River, the Green River below its confluence with the Yampa River, the upper Colorado River (including the lower Gunnison River), and the lower San Juan River (USFWS 1991, 1994a). The present distribution and abundance of the Colorado pikeminnow in the upper Colorado River ~ has been documented thoroughly by Valdez et al. (1982) and Osmundson and Burnham (1996). The distribution appears to have changed little from the time of earlier surveys conducted by Holden and Stalnaker (1975) and Seethaler (1978). The ISMP has provided additional information on abundance and short-term population fluctuations (McAda et al. 1994a,b,1995; Osmundson et al. 1996), and there is some ~ evidence of recent, and relatively high levels of recruitment during some years. Although the Colorado pikeminnow is classified as a warmwater species, adults are cold tolerant (Wick and Hawkins 1989). Most adults move to upstream reaches after spawning and establish home ranges in cooler tributary streams for most of the year. ~ Evidence for this pattern in the Green River basin includes tag returns, dead fish, photos by anglers, and other unpublished records on file at the USFWS office in Vernal, UT. In unblocked streams, some adult fish move as far upstream as the lower portions of Coldwater trout reaches (e.g., Steamboat Springs in the Yampa River and Swallow Canyon in the upper Green River), although most of the adult fish select slightly warmer . areas for residence during most of the year (e.g., Yampa River from Williams Fork to Juniper Springs, Colorado; USFWS 1987). The two largest extant populations occur in the Green River basin: one that spawns in the lower Yampa River, and one that spawns in the lower Green River. Adult pikeminnow occupy about 520 mi of river channel divided almost equally between the ~ Green River (240 mi) and its two main tributaries, the Yampa and the White rivers (280 mi). Adults are found in the Yampa River from its mouth to Craig, in the White River from its mouth to Meeker, and in the Green River from the Yampa confluence upstream to Swallow Canyon in Browns Park. The Green River mainstream below its junction with the Yampa River was once thought to contain about 8,000 adult fish, or about 23 ~ fish per mile (Tyus 1991), and the Green River basin (including Green, Yampa, and White rivers) probably supports twice that many adults. The Colorado pikeminnow population in the UCR consists of approximately 600 - 650 subadult and adult fish (Osmundson and Bumham 1996). McAda and Kaeding 5