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varies from site to site. Some populations seem to be pure, but others contain a high percentage of hybrids. Prospects for the Future Because of its more widespread distribution and greater abundance, and its utilization of artificially created habitat, the razorback sucker seems to have a more hopeful future than do the three species pre- viously discussed. The problem of successful repro- duction must be solved before the continued existence can be assured and increased abundance can be effec- ted. Adult razorback suckers flourish in reservoirs and pond type environments, but the young have not been found in such environments. It would be most important to know what the optimum spawning condi- tions are, in regard to depth, velocity, and sub- strate. It will also be important to learn what associated non-native fishes are least harmful and what species are most harmful to successful reproduc- tion. Artificial propagation of razorback suckers has been conducted for several years at the Willow Beach Federal Hatchery, Arizona. Populations could be main- tained in reservoirs by stocking fish reared in a hatchery, but if reproduction is not successful in a reservoir or a section of a river, reproduction by stocked razorback suckers cannot be expected. Because the razorback sucker has not yet been listed as endangered or threatened by the federal government, it has not been eligible for federally funded projects on endangered species, and has re- ceived much less attention than have the squawfish and humpback chub. It would be useful, for a better understanding of the species, to document its occur- rence in all off-channel pond habitats, correlating the abundance of razorback suckers with habitat char- acteristics such as size, shape, depths, and associa- ted fish species. An analysis of the common demoni- nators of the factors that favor the success of the species could then be made. If this were done, future man-made modifications might be designed to benefit the razorback sucker and perhaps the squawfish. 25