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have failed to survive to the juvenile stage in all habitats studied. When stocked in diverse, fishless arenas, however, larvae typically mature without augmentation or enhancement of food supply. Twenty-three species have been accidentally or intentionally introduced into Lake Mohave as sportfish or forage, with at least three-fourths known or predicted to consume eggs or larval fishes. Many of the same species also are introduced throughout the Colorado River basin. It seems unlikely that efforts to eradicate or suppress these predators will be successful, and certainly not in time to benefit razorback suckers. Alternatives for stabilization: Alternatives for stabilizing the razorback population in Lake Mohave seem to hinge on enhancement of survival in early life history stages. It is clear that the species can be secured for the future either through culture or some other human intervention that includes a period of protective custody. We, however, share the deep concerns of a growing number of conservationists and fisheries managers (Isacksson, 1988; Meffe and Vrijenhoek, 1988; Hindar et al., 1991; Waples, 1991) that genetic variability will suffer if ex situ captive breeding is applied exclusively. Many imperiled species are so numerically and genetically depleted by the time recovery efforts are initiated that maintenance of any genetic variability at ali is a major concern. For razorback suckers this is not the case, since the relatively large, remnant population retains considerable variability as indicated by its high mtDNA diversity (Table 3). The existing population must have been produced by a large number of genetically variable females occupying the pre-development Colorado River. The species' longevity has allowed persistence of genetic diversity long enough for us to recognize and respond to its presence, hopefully in a beneficial way. We examine three available options for management of razorback sucker in Lake Mohave, keeping in mind the need to produce large numbers of fish as well as maximize 24