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those collected in this study were perhaps 8 to 12 years of age. Vanicek and Kramer (1969) documented a decrease in fish growth rates in the Green River from 1958 to 1965 which they attributed to the cold water flowing from the recently constructed Flaming Gorge Dam. This condition is likely to occur in the White River if a dam is built. The sex of the squawfish could not be determined by external features or by expressing sex products. Seethaler (1978) reported that squawfish greater than 400 mm in length are usually mature, therefore, those collected in this study should have been mature. Since no nuptial tubercles were observed, the fish captured in July were either immature, mature but not ripe, or were females. Specimens collected in September could not be sexed since both male and female appear similar after spawning season. In this study, squawfish were collected in relatively shallow water. One fish was captured in 3 ft (1 m) of water along a low sand bar bank where the bottom was a combination of sand and silt. Two other fish were captured immed- iately downstream from a shallow sand bar where the depth was about 4 ft (1.3 m). Finding fish in waters of this depth may be a function of the efficiency of the sampling gear rather than habitat preference of the fish. Electivity curves derived for adult squawfish demonstrated that the fish prefer eddies, runs and backwaters with a predominately sand substrate (Holden, 1977). Velocity may vary from 0 to over 3 ft (.9 m) per second and depth from 1 ft (.3 m) to 9 ft (3 m). Other authors have reported similar findings (Seethaler 1978). Young-of-the-year squawfish have been found in shallow backwaters where there is little current and a silt bottom (Holden, 1977). Juvenile squawfish have also been found in the deeper sections of backwaters (Vanicek, 1967; Holden, 1977). Although this type of habitat was extensively sampled throughout this study, no young squawfish were found. This finding suggests that the upper 42 mi (76 km) of the White River is not an important squawfish spawning area. Humpback Chub Complex (Gila cypha x Gila elegans) The humpback chub (Gila cypha) has never been abundant in the Colorado River Basin even though it is uniquely suited to the swift currents of large rivers. It is distinguished by the large nuchal hump which rises abruptly from behind the head. Specimens most nearly representing the G. c ha type species, have been collected from the Colorado River in Ruby Canyon (McAda et al., 1977). Individuals with smaller nuchal humps and which have some of the charac- teristics of the bonytail chub (G. ele ans) are more commonly found. The