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4 <br />tion), Bruce DeMarais and W.L. Minckley (Arizona State University), R. <br />Riley (National Park Service), and personnel of Cottonwood Cove Resort <br />and Marina all provided assistance. Permits were issued by the States <br />of Arizona and Nevada. <br />STUDY AREAS <br />Spawning adult razorback suckers concentrate in Arizona Bay, <br />Hammerhead Cove, and Six Mile Area of Lake Mohave (Fig. 1). The first <br />two locations were selected as primary sites, Arizona Bay because it <br />supports a large aggregation of suckers (Bozek et al. 1984, Langhorst et <br />al. 1985), which are readily observed and sampled during calm weather, <br />and Hammerhead Cove because larvae are abundant and readily observed and <br />captured there except during turbulence of major storms. Both areas <br />were regularly visited and sampled from January to May 1985. Physical, <br />chemical, and biological features of Lake Mohave were previously <br />described by Allan and Roden (1978), Priscu (1978), Baker and Paulson <br />(1980), Paulson et al. (1980); Bozek et al. (1984); and Minckley (1983). <br />Adjacent to Arizona Bay is a natural backwater, separated from Lake <br />Mohave by a wave-formed spit of coarse gravel (Fig. 2). This protected <br />habitat was selected for rearing razorback sucker larvae in isolation. <br />The backwater has maximum depths of 1.7 to 3.7 m and surface areas of <br />0.85 to 2.1 ha at lake elevations of 193.5-195.5 m, respectively, and is <br />fed by Lake Mohave water that exchanges freely through the porous berm. <br />Water temperatures paralleled those of the lake, but averaged slightly <br />cooler (-1.10C) in winter and warmer (+ 1.80C) in spring; thermal <br />differences were most pronounced during early morning in winter (maximum <br />observed T = 2.OoC) and late afternoon in summer (maximum T = 3.20C).