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18 <br />of about 12 mm, then apparently disappear. Large numbers of larvae have <br />been found only in the vicinity of Hammerhead Cove, Arizona, approxi- <br />mately 8 km down-reservoir from Arizona Bay. Larvae have generally not <br />been sampled from the water column at night without first attracting <br />them with bright light to the surface, and few were taken during <br />daylight. Food habit analysis provides some evidence that larvae forage <br />at or near bottom. We suggest that benthic larval razorback suckers <br />move offshore into deeper water adjacent to spawning areas. Three <br />independent sources of evidence support this conclusion: (1) sucker <br />larvae eat at least some benthic organisms, (2) larvae were not captured <br />in surface water away from shorelines, and (3) larger larvae apparently <br />inhabited deeper portions of the Arizona Bay backwater. Two potential <br />fates await larvae in the limnetic habitat: (1) being eaten, or (2) <br />being transported downstream. <br />While we know that predation occurs in near-shore habitats, we <br />anticipate this factor to be significantly more important off-shore. <br />The primary potential predator there being threadfin shad, which <br />occupies primarily pelagic habitats during winter (Johnson 1969), feeds <br />on a variety of planktonic and benthic organisms, including larval <br />fishes (Burns 1966, Ingram and Ziebell 1983), and is undoubtedly the <br />most abundant fish species in Lake Mohave. Although temperature- <br />sensitive, threadfin shad may move throughout the lake without this <br />restraint in winter when Lake Mohave is isothermal (Priscu 1978, Paulson <br />et al. 1980). Populations of threadfin shad and larval razorback sucker <br />may thus overlap in time and space, and predation by the former has <br />potential to reduce densities of the latter. This may have occurred, <br />but gone undetected, in the Arizona Bay backwater.