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364 CHAPTER 15 recent declines. The protected fishes included threatened and endangered species on FWS lists and those proposed for listing. Species of special concern are not protected by law but were considered either more secure than protected species or too poorly studied to determine if they need full protection. Johnson listed 517 taxa, including described and undescribed species and subspecies, that had legal protection and 709 of special concern in the United States and Canada. By 1986, over 90% of the fishes listed by Deacon et al. (1979) as in need of assistance had at least special-concern status, and 62% were fully protected by state or federal law. Only four states and six provinces had no protected fishes or fishes of special concern. A sobering statistic was that 56% of the described fish species of the United States and Canada were receiving some degree of protection and 32% were fully protected by one or more governments under endangered species laws in all or a portion of their ranges. The most up-to-date and authoritative information on endangered, threatened, and special concern fishes of North America is that of Williams et al. (1989). The authors, members of the American Fisheries Society Endangered Species Com- mittee, updated the list compiled by Deacon et al. (1979) by adding 139 new taxa and removing 26. Williams et al. (1989) listed 364 fishes in North America that deserved endangered (103), threatened (114), or special-concern status. Twenty- two of the listed fishes were endemic to Canada, 254 to the United States, and 123 to Mexico. Fifty-six of the new taxa on the list were Mexican fishes added because of new information on their status and the serious degradation of aquatic habitats in that country. Fishes of the southwestern and southeastern United States showed most adverse impacts of habitat loss and introductions of exotic species. No fish was removed from the 1979 list because of successful recovery efforts. Although recovery plans have been approved for 47 of the 82 species of U.S. fishes listed as threatened or endangered by FWS'(1990), the American Fisheries Society lists far more fishes than does the FWS. Williams et al. (1989) stated that recovery efforts had been locally effective for some species but that North America's fish fauna has generally deteriorated. Future management for conser- vation of entire ecosystems and establishment of long-term monitoring programs for fish populations and aquatic habitats were encouraged. 15.4 CASE HISTORIES 15.4.1 Causes of Fish Endangerment Ono et a!. (1983) presented many case histories on rare and endangered fishes. North American fishes have been forced to the brink of extinction by several human activities. Our case histories and those presented by Ono et al. illustrate that habitat alteration, introduction of nonnative species, and overexploitation have had the greatest impacts on native fishes. Lake sturgeon, shortnose sturgeon, ciscoes of the Great Lakes, Atlantic (Acadian) whitefish, and the cui-ui have declined significantly because of their desirability as food fish. Introduction of nonnative fishes has significantly impacted western trouts and fishes of such diverse habitats as North American deserts, the Colorado River system, Pacific coast streams, and Texas springs. However, there is no doubt that human capacity to change habitats has been the most significant threat to native North American fishes. In their case histories, Ono et al. (1983) reviewed situations in