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<br />660
<br />
<br />GREAT BASIN NATURALIST
<br />
<br />Vol. 46, No.4
<br />
<br />them into the shallow nursery habitat that
<br />forms during this period in the Green River.
<br />Such a temporal adaptation fits in well with
<br />the life strategy of P. lucius, for the length of
<br />exposure of P. Lucius young to predators is
<br />reduced. This reduced time for the young to
<br />feed is balanced by delivering them into ideal
<br />conditions for growth.
<br />This species selects highly oxygenated
<br />white-water rapids and riffles for spawning
<br />sites that may be 100 km or more from their
<br />preferred adult habitat at that time (Archer
<br />and Tyus 1984). Although the mechanism by
<br />which these fish congregate in spawning areas
<br />is unknown, a homing response (Tyus 1985)
<br />could result in sufficient breeding adults re-
<br />turning to a small area to insure good genetic
<br />recombination and, therefore, maintain a high
<br />degree of genetic diversity in the population.
<br />
<br />Natural Adaptations
<br />and Controlled Systems
<br />
<br />Ptychocheilus Lucius evolved as a species
<br />adapted to conditions existing at the close of
<br />the Cenozoic era. These same adaptations en-
<br />abled it to compete and survive in the isolated
<br />and depauparate Colorado River Basin in the
<br />Holocene until the coming of man. Although
<br />cause-effect relationships between water de-
<br />velopment and the decline of the Colorado
<br />squawfish have not been proven de facto, it is
<br />generally agreed that such development neg-
<br />atively affects the fish (Ono et al. 1983). The
<br />life strategies developed from comparing life
<br />history attributes of P. Lucius with late Ceno-
<br />zoic climatic, geologic, and fossil records sug-
<br />gest that evolving life strategies that adapted
<br />P. Lucius to the natural system would ill befit
<br />the fish to a controlled system.
<br />Paramount in the life strategy of P. Lucius is
<br />the need for unimpeded movement within
<br />the riverine system, and blockage of major
<br />stream sections where P. Lucius occurs has
<br />resulted in the extirpation of the fish from
<br />these areas (Tyus 1984). In addition, the
<br />downstream transport of larva and establish-
<br />ment of shallow euphemeral embayments for
<br />nursery areas are needed, and a proper dis-
<br />charge regime must be maintained for spawn-
<br />ing and rearing of young.
<br />Life strategies proposed herein for P. Lucius
<br />need refinement and further substantiation.
<br />Only by understanding these strategies, how-
<br />ever, can we place its evolution in proper
<br />context and provide for its future.
<br />
<br />ACKNOWLEDGMENTS
<br />
<br />The research upon which concepts in this
<br />paper are developed was supported, in part,
<br />by the Fish and Wildlife Service, Bureau of
<br />Reclamation, National Park Service, Bureau
<br />of Land Management and the States of Colo-
<br />rado and Utah. Principal field personnel in-
<br />cluded C. W. McAda, B. D. Burdick, K. C.
<br />Harper, R. M. McNatt, J. J. Krakker, Jr., W.
<br />B. Harned, E. J. Wick, and D. L. Skates.
<br />Administrative direction was furnished by W.
<br />H. Miller and D. L. Archer. My thanks are
<br />given to W. R. Hansen and R. L. Jones, who
<br />provided suggestions for the manuscript.
<br />
<br />LITERATURE CITED
<br />
<br />ARCHER. D. L., AND H. M. TYus. 1984. Colorado squawfish
<br />spawning study, Yampa River. U.S. Fish Wildl.
<br />Serv., Colorado River Fish. Proj., Salt Lake City,
<br />Utah. 34 pp.
<br />ARCHER. D. L.. H. M TYUS. AND L. R. KAEDING. 1985.
<br />Colorado River fish monitoring project. Final re-
<br />port. U.S. Fish Wildl. Serv., Colorado River Fish.
<br />Proj., Salt Lake City, Utah.
<br />BECKMAN, W. C. 1952, Guide to the fishes of Colorado.
<br />University of Colorado Museum, Boulder, Colo-
<br />rado. 110 pp.
<br />HAYNES, C. M., T. A. LITLE, E. J. WICK, AND R. T. MUTH.
<br />1984. Larval Colorado squawfish (Ptychocheilus
<br />luaus Girard) in the upper Colorado River Basin,
<br />Colorado. 1979-1981. Southwest. Nat. 29: 21-34,
<br />HOLDEN, P. B.. AND E. J. WICK. 1982. Life history and
<br />prospects for recovery of Colorado squawfish.
<br />Pages 98-108 in W. H. Miller, H, M. Tyus, andC.
<br />A. Carlson, eds., Fishes of the upper Colorado
<br />River system: present and future. West, Div.,
<br />Amer. Fish. Soc" Bethesda, Maryland. 131 pp,
<br />MILLER R. R. 1961. Man and the changing fish fauna of
<br />the American Southwest. Pap. Mich. Acad. Sci.,
<br />Arts, Lett. 46: 365-404.
<br />MILLER. W. H., D. L. ARCHER, H. M. TYus, AND K. C.
<br />HARPER 1982. White River fishes study. Final
<br />report. U.S. Fish WildI. Serv., Colorado River
<br />Fish. Proj., Salt Lake City, Utah.
<br />MILLER. W. R, D. L. ARCHER, H. M. TYus, AND R. M.
<br />McNATt. 1982. Yampa River fishes study. Final
<br />report, U.S. Fish Wildl. Serv., Colorado River
<br />Fish. Proj" Salt Lake City, Utah.
<br />MINCKLEY. W. L. 1973. Fishes of Arizona. Arizona Game
<br />and Fish Department, Phoenix, Arizona.
<br />ONO. R. P., J. D. WILLIAMS, AND A. WAGNER, 1983. Vanish-
<br />ing fishes of North America. Stone Wall Press,
<br />Inc., Washington, D. C. 257pp.
<br />SMITH, G. R. 1981. Effects of habitat size on species rich-
<br />ness and adult body sizes of desert fishes. Pages
<br />125-171 in R. J. Naiman and D. L. Soltz, eds.,
<br />Fishes in North American deserts. John Wiley and
<br />Sons, New York.
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