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ENDANGERED SPECIES 377 populations, but other subspecies can be conserved by protecting only a few populations. Their data suggested that some subspecies of cutthroat trout have long evolved separately from others and that taxonomic revision of the species is needed to (1) reflect these distinct evolutionary histories, and (2) allow develop- ment of good conservation plans for the diverse groups now considered a single species. Rearing and reintroducing endangered fishes have generally met with limited success. Ono et aI. (1983) discussed several failed attempts to propagate rare fishes. But, for some species such as the endangered cui-ui of Pyramid Lake, Nevada, artificial propagation is the key to survival. State and federal agencies at first seemed reluctant to embrace reintroduction because of its potential to limit other water uses. Nonetheless, reintroductions of rare fishes began in the southwestern United States in the early I 980s. Elimination of the requirement that critical habitat be designated when species were listed and provision of experi- mental populations by the 1982 ESA amendments initially stimulated increased interest in reintroduction. However, regulations6nalized in 1984 were so com- plicated that many reintroduction plans were disrupted again (Rinne et at. 1986). Williams et aI. (1988) examined recovery plans for 39 endangered and threatened U.S. fishes and found that 82% of them called for reintroductions to establish new populations, begin artificial propagation, or set up educational exhibits. Many fishes have been introduced to North America, primarily to provide sport and food (Courtenay and Kohler 1986), and others have been moved within North American countries to areas outside their native ranges. Effects of such introduc- tions may include habitat alteration, introduction of parasites or diseases, reduction in growth or survival (or even elimination) of native fishes, and changes in community structure. Adverse effects of introduced exotics have contributed to 66% of fish extinctions in North America in the past century (Miller et at. 1989). When an introduction seems the only solution to a problem, guidelines to facilitate sound decision making should be followed (see Chapter 12). Artificial barriers have been used to separate endemic rare fishes from potential predators, competitors, or sources of hybridization (Ono et al. 1983). Threatened fishes may be the objective of properly managed sport fisheries. Kucera et at. (1985) and Gresswell (1988) described introductions of threatened greenback and Lahontan cutthroat trouts to establish sport fisheries. Sport fisheries should not be developed at the expense of natural populations or habitats. Although exploitation of endangered fishes is controlled as mandated by the ESA, regulations may be necessary to restrict their incidental catch or limit the extent to which they are taken by mistake. Such regulations are often considered a form of people management. 15.5.2 Managing People Economic, political, and social constraints often have strong bearing on decisions related to managing endangered fishes. The snail darter controversy and other case histories illustrate this point. Conflicts between endangered fishes and construction projects or other human activities with significant economic, politi- cal, and social support are certain to continue. Simply gaining funding for research on and management of endangered fishes requires consideration of these factors. Fish and game agencies continue to struggle to support nongame programs with ~