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<br />l"' ~
<br />
<br />Allendorf
<br />
<br />are many more species of fish than mammal and bird
<br />species combined (Mayr 1969).
<br />The dependence of fish on water has also brought
<br />many species into conflict with humans over increas-
<br />iflgly valuable water resources. An analysis of the source
<br />of threats to the fishes of the United States is revealing.
<br />Ono, Williams, & Wagner (1983) listed five categories
<br />of threats to 151 fish species that they considered to be
<br />endangered or threatened: habitat alteration, overuti-
<br />lization for commercial purposes, disease, introduction
<br />of exotic or non-native fishes, and restricted natural
<br />range. Individual species were threatened by any com-
<br />bination of these five factors. A surprising 98% of all
<br />species were threatened by habitat alter . . The next
<br />most common t eat was introduced fisltes, which
<br />threatened 37% of the species. The final major threat
<br />was restricted natural range (24%). Less than 5% of the
<br />species were threatened by either commercial harvest-
<br />or disease.
<br />The paper in this issue by Meffe & Vrijenhoek (1988)
<br />considers genetic aspects of conservation and recovery
<br />programs of fishes in the deserts of western North Amer-
<br />ica, where the conllict for water resources has been
<br />most acute. Over 75% of the U.S. federally listed endan-
<br />gered species occur in the Southwest (Sheldon 1988).
<br />Meffe & Vrijenhoek compare two models of genetic
<br />population structure in desert fishes based upon geo-
<br />graphic isolation and gene flow. They emphasize "the
<br />need to incorporate experimental studies of population
<br />genetics and fitness into management of endangered
<br />fishes. "
<br />Sheldon's paper in this issue describes conservation
<br />problems intrinsic to species living in flowing water be-
<br />cause of the geometry of river systems. He emphasizes
<br />the importance of recognizing the threats of fragmenta-
<br />tion of drainage networks by impoundments and the
<br />homogenization of faunas by interbasin connections and
<br />introductions. His analysis of these problems makes the
<br />important conclusion that biogeographic considerations
<br />are essential in any plan for the conservation of North
<br />American fishes.
<br />These three papers provide different perspectives on
<br />the challenges to conservation biology provided by
<br />fishes. The most striking common theme of these papers
<br />is the issue of the objectives of fish conservation biol-
<br />ogy. What should we be trying to "conserve"? Each pa-
<br />per struggles with this question, and each concludes
<br />with a different answer.
<br />
<br />Acknowledgments
<br />
<br />I thank Pete Brossard for inviting me to organize the
<br />symposium, the Society for Conservation Biology for
<br />providing financial assistance for travel to the speakers,
<br />Dave Ehrenfeld for his help and patience, the reviewers
<br />
<br />Conservadon Biology of Fishes
<br />
<br />147
<br />
<br />of these papers for their time and helpful comments, and
<br />Nils Ryman for his suggestions on this paper. I was sup-
<br />ported by grant BSR.86000108 from the National Sci-
<br />ence Foundation while this paper was prepared.
<br />
<br />Literature Cited
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<br />Allendorf, F. W., and R. F. Leary. 1988. Conservation and dis- /
<br />tribution of genetic variation in a polytypic species, the cut. .
<br />throat trout. Conservation Biology 2:170-184.
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<br />Allendorf, F. W., N. Ryman, and F. M. Utter. 1987. Genetics and -./
<br />fishery management. Past, present, and future. Pages 1-19 in
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<br />Bogart, J. P. 1980. Evolutionary implications of polyploidy in
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<br />FAOIUNEP. 1981. Conservation of the genetic resources of I
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<br />Federal Register. 1987. Endangered and threatened wildlife
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<br />Goode, G. B. 1898. Pisciculture. Pages 126-129 in the Ency-
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<br />Komfield, I., D. C. Smith, P. S. Gagnon, and J. N. Taylor. 1982.
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<br />Mayr, E_ 1969. Principles of Systematic Zoology. McGraw-Hill
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<br />Meffe, G. K., and R. C. Vrijenhoek. 1988. Conservation genetics
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<br />Meyer, A. 1987. Phenotypic plasticity and heterochrony in
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<br />
<br />Conservation Biology
<br />Volume 2, No.2, June 1988
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