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eddies formed downstream of debris fans (Valdez and RyeI1995). In larger rivers of the Upper Colorado River Basin humpback chub were found in relatively deep (mean =10.3 ft) and slow velocity (mean =0.6fi1sec) water. Karp and Tyus (1990) and additional data presented in this study suggested that humpback chub in the Yampa River use low velocity habitats near shore. Humpback chub used deeper habitats when available, however, during baseflow periods the abundance of deep-water habitat declines, fish are capable of using shallower habitats. Colorado pikeminnow and humpback chub are members of the native fish community of the Colorado River Basin. The following sections describe other members of the Yampa River fish community, both native and nonnative. These fishes are dependent on the primary and secondary production present in the river. The remainder of the this chapter describes habitat associations and diet of select native and nonnative fishes to provide a context for interpreting radio telemetry data for the Colorado pikeminnow and humpback chub. Other native fishes Native fish species present in the potamon reaches of the Yampa River include flannelmouth sucker Catostomus latipinnis, bluehead sucker Catostomus discobolus, roundtail chub Gila robusta, and speckled dace Rhinichthys osculus. All of these species are potential prey for the Colorado pikeminnow. In a recent study, the Colorado Division of Wildlife made population estimates at two sites on the Yampa River in September 1998. The native fish component comprised 71% of the fish over 15 cm caught downstream of Sunbeam (RN60-64), but were only 14% of the catch at Duffy Tunnel (RM 104.5-110.0) (Anderson, in press). Historic distribution of the tlannelmouth sucker included medium to large streams throughout the upper and lower Colorado River basin (Joseph et al. 1977; Arizona Game and Fish 1996). Currently flannelmouth sucker populations in the lower basin have been reduced and restricted to areas of suitable habitat (Minckley 1985). In the upper basin this species still persists in much of its original range (Holden and Stalnaker 1975); however, flannelmouth sucker populations have become lost or depleted in areas that are influenced by impoundments (Chart and Bergesen 1992). Flannelmouth suckers remain common in the upper basin in medium to large streams with natural temperature and flow regimes. Carlson et al. (1979) reported that flannelmouth suckers composed between 12.5% and 53.7% of the total fish captured from July 1975 through October 1977 at six sites on the Yampa River between Dinosaur National Monument and the town of Hayden, Colorado. The percent composition offlannelmouth sucker, for all fish over 15 cm, was estimated to be 37% downstream of Sunbeam (RM 60-64) and 7 32