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Larval razorback suckers were reported to drift passively from spawning sites in Lake Mohave, Nevada (Marsh and Minckley 1989; Minckley et al. 1991). Some razorback larvae were collected up to one-fourth mile from the mouths of backwaters indicating that the larvae have locomotion ability, at least in low water velocity habitats (Wick, 1996, personal communication). Adult razorback suckers exhibited moderate migratory movements of 12 to 16 miles from feeding and resting areas to spawning sites (Tyus 1987; Tyus and Karp 1990). However, individual fish have been documented to move more than 60 miles and one fish moved about 129 miles (Tyus 1987). Razorback sucker larvae are known to drift downstream from spawning areas but habitats used by juvenile fish has not been documented because few juveniles have been captured (Carter et al. 1986; Maddux et al. 1993; Marsh and Minckley 1989; Minckley et al. 1991). Minckley et al. (1991) documented that razorback sucker larvae occupy shallow areas within a few weeks after hatching. Razorback suckers flourish in quiet water habitats such as off-channel ponds where they grow rapidly (Osmundson and Kaeding 1989). Valdez and Wick (1983) stated that backwaters and embayments are important nursery habitats to juvenile endangered fishes because they are low water velocity habitats with warmer water temperatures and more food organisms than the adjacent river. Adults of this species generally occupy quiet eddies and pools in the mainstem rivers (Miller et al. 1982). During high runoff periods, adults congregate in large backwaters at the mouths of rivers, flooded bottomlands, and off-channel ponds that have a connection to the river (Tyus and Karp 1990). Razorback suckers spawn over or near gravel bars in water that is 2 to 3 feet deep with water velocity of about 1.0 foot per second (Wick et al. 1982). Kidd (1996) reported that he observed spawning razorback suckers in significant numbers between 1971 and 1980 at five sites on the Upper Colorado River, two of which are between Palisade and Rifle. These sites were all greater than 5 acres in area, more than 1,500 feet long, generally 3-5 feet in depth, and did not depend entirely upon the river to maintain water levels. Kidd attributed the rapid decline of the razorback sucker population in the Upper Colorado River to the loss of spawning sites after areas near DeBeque were lost during the high water years of 1983 and 1984 and during Interstate Highway construction. A-2