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1 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. phase of a propagation program is fundamental in the recovery of endangered species because the species must possess sufficient genetic diversity to allow survival and recruitment of the fish in altered and partially restored environments. 1 1 The importance of maintaining detailed and accurate propagation records for captive broodstocks cannot be overemphasized. Records should include the origin, genetic profile, and unique identifying number of each adult broodfish as well as its production record and progeny performance. Genetic characteristics of broodstocks and progeny must be known so that augmentation or reintroduction efforts can be monitored and evaluated to determine survival of hatchery-reared fish and their interaction with wild stocks (Gauldie 1981; Hynes et al. 1981). It is especially important to obtain a random sample of fish that represents the donor population by sampling adults within and among spawning times throughout the spawning range of that stock. The number of wild fish removed at any one time should be limited so that the remaining wild fish are not adversely affected by their removal unless the species is in immediate danger of extinction. In general, no more fish should be removed than can be spawned at a particular time or maintained in available holding facilities. Following successful contribution to the F, generation, wild fish should be returned to the river reach where they were collected. If further stocking is deemed necessary, additional wild fish can be captured and used to supplement the genetic diversity in broodstocks. 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 19