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