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If sufficient adult endangered fish are available and removal from the wild will not jeopardize the genetic characteristics of the founder stock, a minimum target of 50 adults (25 males and 25 females) should be used to develop broodstocks since the likelihood of inbreeding will be minimized. Broodstocks will be developed through paired matings that produce pedigreed family lots. An inbreeding rate of 1% was estimated for an effective population size of 50 fish that is considered to be acceptable for maintaining the genetic diversity of wild fish stocks. When stocks are low, a minimum breeding strategy using a 5 X 5 di-allele cross will be used to develop broodstocks. A 5 X 5 breeding strategy has an effective population size of 10 fish and an estimated inbreeding rate of 5%. In the event that 5 males and 5 females are not available, a factorial mating will be used to capture the genetic contribution from all fish of the least numerous sex. However, additional wild adults will be used to supplement the broodstock that are developed from a 5 X 5 or factorial cross when they are available to increase the effective population size that will, in turn, reduce the estimated inbreeding rate. Adaptive management will be used to implement these genetics management guidelines. The guidelines will be reviewed annually by the Biology Committee and revised if necessary. II. PHILOSOPHY, MISSION, AND GOALS FOR GENETICS MANAGEMENT A. Background. Various water development activities in the Upper Colorado River Basin have presented barriers to fish passage or changed the historic water regime of the river system, thereby affecting streamflows, water temperatures, and low velocity habitats that are crucial to the successful recruitment of endemic fishes (U.S. Fish and Wildlife Service 1987a, 1987b, 1990a 1990b, 1991). Nonnative fishes were introduced, either intentionally or accidentally, that have become established in the river and are suspected to be competitors with, or predators on, the native fishes (Miller et al. 1982). These biological and environmental changes, as well as others, have resulted in the four endemic large river fishes, razorback sucker (Xyrauchen texanus), bonytail (Gila elegans), humpback chub (Gila cvpha), and Colorado squawfish (Ptychocheilus lucius), being listed as "endangered" under the Endangered Species Act of 1973, as amended. To protect the endangered fishes while allowing water development to continue in the Upper Colorado River Basin to meet the needs of society, the U.S. Fish and Wildlife Service coordinated an effort to develop a Recovery Implementation Program (Program) for endangered fish (U.S. Fish and Wildlife Service 1987a, 1987b). This effort includes participation by many potentially affected interests in the upper Colorado River: the States of Colorado, Utah, and Wyoming; U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, Western Area Power Administration, water development interests, and environmental organizations (Wydoski and Hamill 1991). J