7031 - Laserfiche WebLink

Home Browse Search

~DJ/l I C(I q ((< ()7'c~1 ENDANGERED AND THR.EATENED FISHES OF THE WEST James E. Deacon' ABSTRACT.- The endangered and threatened fish fauna of the United States exhibits problems resulting primarily from habitat modification by man. The evolutionary history of the fauna has left it especially sensitive to biotic interactions. In addition, many forms are of such restricted distribution that the entire taxon can be destroyed by very minor perturbations. The effects of habitat modification on woundfin and roundtail chub in the Virgin River of Utah, Arizona, and Nevada are discussed. Parasitism by Lemea on White River springfish is shown to coincide with population decline in some, but not all, cases. Population declines of Pahrump killifish are related to biotic inter- actions with both goldfish and mosquitofish. Population size of Devils Hole pupfish are shown to be quite responsive to small changes in habitat availability. Fishes of the West are affected by the same general kinds of ecological problems that are causing extinctions throughout the world. The interplay of economics with perceived value in society has led us into the numerous ecolOgical problems facing us today. There is some evidence to suggest that society is making some preliminary ef- fort to slow the rate of extermination. Perhaps this is happening because the conclusions of ecologists, philosophers, and theologians regarding the relationship of man and environment are to some extent being translated into legisla- tion as well as into conventional wisdom. .1 The fish fauna of the western United States has frequently been characterized as one hav- ing a relatively low diversity and containing an unusually high percentage of endemic taxa exhibiting limited distributions (Miller 1959, Smith 1978). These appear also to be the primary features contributing to the fact that much of the fauna is threatened to some degree. Recently, the Endangered Species Com- mittee of the American Fisheries Society compiled a listing of threatened fishes of North America (Deacon et al. 1979). The fishes on that list from the western United States are presented here as a data base for the general discussion (Tables 5 and 6). The predominant threats to all taxa listed were generalized into five broad categories and each taxon was assigned one or more of these categories. Threat categories were as follows: (1) The present or threatened destruction, modification, or curtailment of the habitat or range. (2) Overutilization for' commercial, sporting, scientific, or educational purposes. (3) Disease or parasitism. (4) Other natural or manmade factors affecting continued exist- ence (hybridization, introduction of exotic or translocated species, predation, competition). (5) Restricted range of the taxon. A com- lDepartment of Biological Sciences, University of Nevada, Las Vegas, Nevada 89154.. --1 parison of threats to western fishes north of Mexico with those to eastern fishes is of gen- eral interest and illustrates significant differ- ences between the two faunas (Table 1). Habitat modification (Category 1) is clear- ly the most prevalent threat to native fishes throughout the world, and this is certainly true ~n North America. There are a few spe- cies in the West, however, that are not now so threatened. No eastern species, however, has escaped problems raised by physical al- teration of the habitat. No western species has been or is threat- ened by overexploitation (Category 2), but about 7 percent of the eastern fishes on the list are or were so threatened. Six species of ciscoes occurring in the Great Lakes were subjected to overfishing by commercial fish- ermen, changes resulting from the in- troduction of the sea lamprey, and general environmental degradation (Scott and Cross- man 1973). In addition, the Atlantic whitefish has been subjected to overfishing as well as habitat alteration. They represent the only fish taxa in the United States or Canada to be on the American Fisheries Society list of threatened species, in part, because of over- exploitation. Disease and parasitism (Category 3) have 41 ---.,. J..