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VIII. STOCKING AS A MANAGEMENT TOOL'FOR ENDANGERED FISH RECOVERY A. Guidelines for Stocking Captive-Reared Endangered Fishes. Suitable habitat must be available in river reaches that are proposed for stocking to increase the likelihood of successful stocking. The reasons for holding, rearing, and stocking endangered fishes are summarized in Box 5. Criteria for holding, rearing, or stocking captive-reared endangered fish, criteria for when to stock, and action required are provided in Box 6. Guidelines for preparation of stocking plans for release of captive-reared endangered fish into the Upper Colorado River Basin are summarized in Box 7. Box 5. Reasons for holding, rearing, or stocking endangered Colorado River fishes. 1. Place endangered fish in refuges to protect genetic diversity in instances where the stock may become extinct in the near future from population declines or catastrophic risk. 2. Production of endangered fishes for experimental stocking to obtain biological, ecological, or environmental information from field experiments that are essential to the recovery effort. 3. Production of endangered fishes for augmentation stocking to enhance severely depleted stocks. 4. Production of endangered fishes for restoration stocking of extirpated populations or stocks. B. Choice of Founders for Broodstock Development. The first priority for obtaining founders for a broodstock is to use founders from the appropriate wild stock or population and to use acceptable breeding strategies that will maintain genetic diversity similar to the wild stock (Kapuscinski et al. 1993). Strategies for broodstock development can be prearranged to reduce genetic risks to wild stocks. Adult fish from each stock evolved life history patterns (other things being equal) that allowed adaptation to their environment in the Upper Colorado River Basin. If the endangered fish stock or population from a specific river reach has been extirpated or is extremely low, then the founders should be obtained from a stock that would be the nearest neighbor from an evolutionary (not necessarily geographic) standpoint. Fish from nearest neighbor stock should exhibit life history patterns similar to the extirpated population and be taken from an environment that has the greatest ecological similarity to the environment where the species is to be restored. If restoration cannot be done by natural reproduction, small numbers of wild founders should be collected from the wild stock to minimize demographic impacts on the genetic resources, life history patterns, and recruitment of the wild stock. 1 1 1 A 11 26 1