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Bluehead suckers feed by scraping periphyton from rocks (Joseph et al. 1977). The mouthparts of the bluehead sucker and other sucker species in the subgenus Pantosteus are specifically adapted for scraping algae from rocks (Sigler and MiJler 1963; Joseph et al. 1977). Vanicek (1967) found that gut samples from bluehead suckers from the Green River contained mud, filamentous algae, and chironomid larvae. Carlson et al. (1979) reported that gut samples from bluehead suckers in the Yampa River contained mostly periphyton and a few invertebrates during August and September 1975. Young bluehead suckers are eaten by piscivorous species. Piscivorous fishes that feed on bluehead suckers primarily include roundtail chub and several introduced nonnative species (Joseph et al. 1977). Most populations of bluehead suckers occur in smaller streams and at higher elevations than those inhabited by Colorado pikeminnow, so bluehead suckers in most systems do not constitute a major food source for Colorado pikeminnow (Joseph et al. 1977). The roundtail chub is endemic to the Colorado River drainage. Historically, roundtail chub commonly occurred in most tributaries of the upper Colorado River Basin (Vanicek 1967; Holden and Stalnaker 1975; Joseph et al. 1977). Holden and Stalnaker (1975) reported that roundtail chub were abundant or common at all sites sampled at the Yampa River, and most sites in the Dolores River. Carlson et al. (1979) found that roundtail chub composed between 2.8% and 14.3% of the total fish captured from July 1975 through October 1977 at five sites on the Yampa River between Dinosaur National Monument and the town of Craig, Colorado. The percent composition of roundtail chub, for all fish over 15 cm, was estimated to be 6.7% downstream of Sunbeam (RM 60-64) and 3.8 percent 50 miles upstream near Duffy Tunnel (Anderson, in press). In the Yampa River most roundtail chubs collected by Carlson et al. (1979) were in eddy or pool habitat. McNatt and Skates (1985) found roundtail chub common at most sites in the Green River and Yampa River in Dinosaur National Monument. Olson (1967) stated that roundtail chub were common in collections in Navajo Reservoir during 1965. Feeding habits of round tail chub are described as "opportunistic" and "sporadic" (Vanicek 1967). Joseph et aJ. (1977) reported that roundtail chubs of all age classes are primarily carnivorous. Young roundtail chub typically inhabit the slower, shallower water along the shoreline of the stream (Sigler and Miller 1963). Young chubs in the Green River consumed primarily aquatic insects (particularly chironomid larvae and ephemeropteran nymphs) (Vanicek 1967; Vanicek and Kramer 1969). Joseph et al. (1977) provided additional evidence of young roundtail chub feeding mostly on aquatic invertebrates found at the bottom of pools and eddies. Most growth in young fish occurs between late May and October (Vanicek 1967). 34