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ECOLOGY AND CONSERVATION OF NATIVE FISHES IN THE UPPER COLORADO RiVER BASIN ]63 was approved in 1979 (U.S. Fish and Wildlife Ser- vice 1979), revised in 1990 (U.S. Fish and Wildlife Service 1990a), and amended and supplemented with recovery goals in 2002 (U.S. Fish and Wildlife Service 2002b). Historic abundance of humpback chub is un- known, and historic distribution is surmised from various reports and collections, which indicate the species presently occupies about 68% of its historic habitat of about 756 km of river. The species exists primarily in relatively inaccessible canyons of the Colorado River basin and was rare in early collec- tions (Tyus 1998). Common use of the name "bonytail" for all six Colorado River species or sub- species of the genus Gila confounded an accurate early assessment of distribution and abundance (Holden and Stalnaker 1975a, 1975b; Valdez and Clemmer 1982). Also, human alterations throughout the ba- sin prior to faunal surveys may have depleted or elimi- UTAH ARIZONA farmi~gton nated the species from some river reaches before its occurrence was documented. Five populations of humpback chub are cur- rently known in the upper basin (i.e., Black Rocks, Westwater Canyon, Cataract Canyon, Desolation/ Gray Canyons, Yampa Canyon; Figure 4), and one from Grand Canyon in the lower basin (U.S. Fish and Wildlife Service 2002b). Small numbers have also been reported from Moab Canyon (Taba et al. 1965; Valdez and Clemmer 1982), Debeque Can- yon (Valdez and Clemmer 1982), Cross Mountain Canyon (Wick et al. 1981), Whirlpool and Split Mountain canyons (Holden and Stalmaker 1975a), Little Snake River (Wick et al. 1991), and White River (Lanigan and Berry 1979; U.S. Fish and Wildlife Service 1982a). Based on historic collections, popu- lations have been extirpated from Hideout Canyon in Flaming Gorge (Bosley 1960; Gau6.n et al. 1960; McDonald and Dotson 1960; Smith 1960), and WVOMING f( CO\..O'U.DO o 50 \00 '50 200250 . I SCALE OF KILOMETERS o 51) 100 ,50 1M tfIfl'" . SCALE OF MILES ----~ --- NaVajO FleservoirN E W MEXICO Figure 4.-Humpback chub popularions (shaded) and recent capture locations of wild bonytail (filled circles) in the upper Colorado River basin.