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Razorback sucker larvae observed or captured in reservoirs occupied nearshore environments over a variety of substrate types and were generally found in the vicinity of spawning areas (Sigler and Miller 1963, Hinckley 1983, Bozek et al. 1984, Marsh and Langhorst 1988). Marsh and Langhorst (1988) collected only one larval razorback sucker in deepwater trawls in Lake Mohave, indicating that larvae did not use these habitats extensively. Larvae in Lake Mohave were generally in shallow water (0.3-1.0 m deep), but have been collected at the surface in water as deep as 4.9 m (Bozek et al. 1984). Gently-sloping terraces of wave-sorted gravel and cobble substrate where adults spawn also provides larval habitat. Larvae spend most of the day in the substrate (Bozek et al. 1984) and sediment-free interstitial spaces that are i well-oxygenated may be important. Habitat of juvenile razorback suckers is even less known than that of larval life stages. Taba et al. (1965) collected several juveniles ("90-115 mm long") in a shallow backwater over mud substrate in the Colorado River near Moab, Utah. During most seasons, adult razorback suckers in lotic environments occupied nearshore and mid-channel habitats, including slow runs, deep eddies, pools, and backwaters over silt and sand substrate, and were sometimes associated with instream cover (Hinckley 1973, McAda and Wydoski 1980, Tyus et al. 1982, Valdez et al. 1982a, Tyus 1987, Osmundson and Kaeding 1989a, Tyus and Karp 1989). During spring and early summer, adult razorback suckers have been captured in large numbers in warm, low-velocity 28