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2 . if not extinct in the lower basin. Therefore, the upper basin, includ- ing Grand Canyon, provides the last possible stronghold for these unique f'ishes. \'This group includes North America's largest minnow ptychocheilus lucius (Colorado squawf'ish); Gila cypha (humpback chub), and Xyrauchen texanus (humpback sucker)--both having abruptly humped backs, hypothe- sized to be adaptations for swift-water environments; Gila elegansj (bonytail chub)--showing streamlined morphology adapted to swift water; Gila robusta (raundtail chub)--a more robust minnow of the upper sections of the basin; Catostomua latipinnis (flannelmouth sucker )--the most cOllD1lOn endemic fim, and Catostomus di scobolus (bluehead sucker )--not a true endemic but found as two polymorphs in the upper Colorado basin. Much of th e upper basin still flows free, but two major reservoirs were built in the 1960's. Flaming Gorge Reservoir is located on the upper Green River, the major tributary of the Colorado. Lake Powell, behind Glen Canyon Dam, is just upriver from Marble and Grand Canyons (Figure 1). t. ). Very little is !mown of the distribution, abundance, or life history requirements of the fishes in the upper basin. Evermann and Rutter (1895) swmnarized the collections made prior to 1894. Since that time few reports have appeared. Wagner and Workman (1961) and Taba, Murphy, and Frost (1965) made collections in the Colorado River below Moab, utah. Smith (1959) and McDonald and Dotson (1960) conducted pre- impoundment surveys in Glen Canyon. A fish eradication program in September, 1962 (Binnes, et. al., 1964) effectively eliminated most of the native species above and for many miles below Flaming Gorge before closure of the dam in November, 1962. Vanicek, Kramer, and Franklin (1970) documented the distribution of native fishes below the dam fol- lowing closure and swmnarized pre impoundment surveys. They found the