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Thaw specimens wets soamwhat largos than your= roundtail chubs found during the same study is the Green Rivas near Jensen, Utah, and are largos than both roundtails and bonytails collected by Vaaicek and Kramer (1969) in the Green River of Dinosaur National Monument. Larger young are expected is Desolation Canyon because of the probable earlier spawning time. The subterminal.mouth of the humpback chub suggests bottom feeding (Miller 1946). This assumption has not been tested since no stomach analyses of this species have been made. Humpback chubs have been observed feeding oa the surface is Desolation Caayoa and several netted at Black Rocks and is Dinosaur National Monument were caught vest' sear the surface (personal come-usicatioa, P. Holden, Logan, Utah; personal communication, N. Asmaatrout, BZM, Moab, Utah). This suggests that the humpback is a surface feeder, as is the bosytail chub (Vaaicek and Rramer 1969). Hinckley (1973) noted that humpbacks caught below Glea Canyon Dam had fed primarily on planktonic crustaceans which apparently originated is Lake Powell. No food habit studies have bees conducted on specimens from more natural environments. Reasons for Decline The major reason for decline of humpback chub populations has been the operation of Flaming Gorge and Glen Canyon dams, and Perhaps Hoover Dam. Impouadmeats-and cold tailwaters created by these dams have eliminated humpback chub populations from significant portions of prior habitat (Vaaicek et al. 1970; Bolden and Stalnaker 1975; Suttkus et al. 1975; Suttkus and Cleaner 1977; Smith et al. 1978)• 1Sie fish eradication program oa~the Green giver prior to closing Flaming Gorge Dam probably adversely affected humpback chub populations in Diaosanr National Monu- ment (Miller 1963, 1964), although pre-eradication studies were sot conducted is this area and, therefore, so objective data are available to support this assumption. - Desolation Canyon and Black Rocks populations have sot been known sufficiently long for population changes to be documented. It seems reasonable to assume. that reduced flews far below the cold, fluctuating 8