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2 <br />during early impoundment (Moffett 1943; Wallis 1951) and below Hoover <br />Dam (Moffett 1942; Dill 1944). Bonytail chubs have not been reported <br />from Lake Mead since 1967, but razorback suckers are frequently sighted <br />in that reservoir (Allan and Roden 1978). Bonytail chubs are now thought <br />to be extirpated throughout most of the lower river. Small populations <br />of razorback suckers still occur in Lake Havasu and Senator Wash <br />Reservoir and scattered individuals inhabit the river and irrigation <br />canals below Parker Dam (Minckley 1973, 1983; Ulmer 1981). Large <br />populations of bonytail chubs and razorback suckers were observed <br />spawning over gravel shelf areas of Lake Mohave during the early 1950's <br />(Jonez and Sumner 1954). Bonytail chubs are now rare in Lake Mohave, but <br />a small population still persists in the reservoir. Razorback suckers <br />are presently considered abundant in Lake Mohave (Minckley 1983). <br />Reservoir spawning activity of razorback suckers has been observed <br />in Lake Mead (Wallis 1951, Jonez and Sumner 1954), Lake Havasu (Douglas <br />1952), Senator Wash Reservoir (Ulmer 1981), and Lake Mohave (Jonez and <br />Sumner 1954). Jonez and Sumner (1954) observed what they believed to be <br />larval razorbacks near spawning areas south of Eldorado Canyon, and <br />Ulmer (pers. comm.) collected larvae near Arizona Bay in 1981. One <br />larval razorback sucker was collected below Hoover Dam in an <br />invertebrate sampler during 1979 (Paulson et al. 1980a). Several <br />razorback eggs and larvae were collected in drift samples in the same <br />area in 1984 (.G. Mueller, pers. comm.). Bonytail chubs also have been <br />observed spawning in Lake Mohave, but larvae have never been collected <br />from that reservoir (Jonez and Sumner 1954). A large number of <br />young-of-the-year razorback suckers were collected from the shores of <br />Lake Mohave prior to filling in the early fifties (Sigler and Miller <br />1963). Juvenile or subadult fish of either species have not been