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16 Backwater nursery habitats were influenced by inundation and resuspension of organic material from shorelines during increased flows and ultimately influenced backwater nursery habitats. This energy source was important for standing crops of fish food organisms (Grabowski-and Hiebert 1989). Backwaters in the Ouray area, where young Colorado squawfish were most abundant, were richer in food than upstream areas studied. Reduced water- level fluctuations in that area resulted in more stable backwater habitats and possibly reduced the export of nutrients and food (Grabowski and Hiebert 1989). Juveniles Colorado squawfish reach about 74 mm total length by age-2; their greatest growth occurs during their third and fourth years just prior to attaining maturity. Little is known about the habitat requirements of juveniles, but they were captured in a variety of shoreline habitats including backwaters and flooded bottomlands. Juvenile Colorado squawfish may be more numerous in the lower Green River (Tyus et al. 1987) because of the downstream drift of larvae. If so, a long-distance upstream movement by juveniles is needed to repopulate upstream areas. Because only large-sized fish are found in the upper Yampa River and the highest concentration of juveniles occur in the lower Green River, upstream movements probably occur during the late juvenile or early adult stages (Tyus 1986 and 1990; Tyus et al. 1987). These movements require unrestricted access, which is considered essential to the species. HUMPBACK CHUB General Status Humpback chub originally inhabited the main stem Colorado River from what is now Lake Mead to the canyon areas of the Green and Yampa River basins. They were considered less common than other endemic fish of the region but occur in fairly large numbers where reproducing populations exist. The greatest concentrations of humpback chub occur in the Grand Canyon portion of the Colorado and Little Colorado Rivers and Westwater/Blackrocks region of the Colorado River. Smaller populations and incidental catches are reported from Yampa .River; Desolation, Gray, and Whirlpool Canyons of the Green River; and Cataract Canyon of the Colorado River. The recovery goals for humpback chub established through the Recovery Program are to "maintain or establish and protect five self-sustaining populations, natural habitat, and two refugia." Adults Humpback chub occur in several canyon-bound sections of the Green River basin, including the lower portion of the Little Snake and Yampa Rivers and Whirlpool, Desolation, and Gray Canyons of the Green River (Holden 1978; Tyus et al. 1982x, 1982b, and 1987; Karp and Tyus 1990x; M. Moretti and E. Wick, pers. comm.). Surveys conducted prior to and after closure of Flaming Gorge Dam indicated that all three forms of Colorado River chubs were locally common in the Green River. This includes bonytail and roundtail chubs in upper Green River above Ouray, Utah. Humpback chubs occurred in Desolation and Gray Canyons and in the Flaming Gorge basin of the upper Green River (Smith 1960;