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These numbers will minimize the likelihood of inbreeding. Broodstocks will be developed through paired matings that produce pedigreed family lots. An effective population size of 50 fish will result in an inbreeding rate of only 1%, which is considered acceptable for maintaining 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. 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. This will increase the effective population size that will in turn reduce the estimated inbreeding rate over time. II. PHILOSOPHY AND GOALS FOR GENETICS MANAGEMENT A. Background. various water development projects throughout the Region have created barriers to fish passage or changed the hydrology of river systems, thereby affecting stream flows, water temperatures, sediment, and habitats that are crucial to the successful recruitment of endemic fishes (U.S. Fish and Wildlife Service 1987a, 1987b, 1990a 1990b, 1991). Non- native fishes have been introduced, either intentionally or accidentally. They have become established and are suspected to be competitors with, or predators on, the native species (Miller et al. 1982). These biological • and environmental changes have resulted in the endemic fishes, razorback sucker (Xvrauchen texanus), bonytail (Gila ele ans), humpback chub (Gila cypha), Colorado squawfish (Ptychocheilus lucius), pallid sturgeon (Scaohirhvnchus albus), Neosho madtom oturus lacidus (N P ), greenback cutthroat trout (Oncorhvnchus clarki stomias) and others being listed as endangered, threatened, or candidate species under the Endangered Species Act of 1973, as amended. To protect endangered fishes, while allowing continued water development, the U.S. Fish and Wildlife Service (Service) coordinated development of the Upper Colorado River Recovery Implementation Program (Program) for endangered fish (U.S. Fish and Wildlife Service 1987a, 1987b).. This program includes participation by the States of Colorado, Utah, and Wyoming; U.S. Bureau of Reclamation, Service, Western Area Power Administration, water development interests, and environmental organizations (Wydoski and Hamill 1991). Similar coordinated partnership approaches have been undertaken for recovery of the greenback cutthroat trout, pallid sturgeon, bull trout, arctic fluvial grayling and others. B. Philosoohv and Goals for Genetics Management. Our philosophy is to maintain the genetic integrity of wild and captive-reared fishes in all waters of Region 6. The rationale for this philosophy is that natural refugia provide a source of preadapted genetic diversity that increases the probability for successful recovery of the species (Krueger et al. 2 40