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<br />
<br />Figure 9. Relationships between the average cohort total length
<br />(TL) at repatriation (release) and recapture (survival) of subadult
<br />razorback suckers in Lake Mohave, Arizona and Nevada (dark-
<br />ened diamonds), and the San Juan River, New Mexico and Utah
<br />(open diamonds), based on cohorts of more than 100 individuals.
<br />The top graph displays the minimum first year survival; the bot-
<br />tom graph, the minimum survival to the fourth year after release.
<br />Benefits to native fishes must be a specified target in any
<br />future endeavors on the lower Colorado River; otherwise the
<br />fishes will disappear. System upkeep and repair, sport-fish
<br />management, alterations that may influence listed fishes and
<br />their habitats, and other manipulations are the concerns of
<br />the various agencies already involved. Enforcement of closures
<br />for security, questions of beneficial use of water, legal con-
<br />cerns over water apportionment, concern for evaporation
<br />from new water surfaces, and other issues will also need
<br />consideration.
<br />Our greatest concern is that nonnatives maybecome es-
<br />tablished in places dedicated to native fish production. It is
<br />unreasonable to expect off-channel, isolated habitats to
<br />entirely avoid vandalism or inadvertent addition of non-
<br />natives. Education and information programs for boaters,
<br />anglers, and others will be essential. Nonetheless, contam-
<br />ination will predictably occur, necessitating renovation
<br />and reestablishment of native populations. This might be
<br />achieved by regularly destroying and reconstructing habi-
<br />tat, introducing a surrogate for natural processes of chan-
<br />nel realignment, aggradation (oxbow filling), and degra-
<br />dation (scour).
<br />232 BioScience • March 2003 / Vol. 53 No. 3
<br />Conclusion
<br />Ongoing programs to manage native fishes in the lower
<br />Colorado River focus on individual species and are largely
<br />without benefit of an overall plan. Their ultimate con-
<br />tributions to recovery are unknown. At best, fulfillment
<br />of the major commitment to native fishes envisioned by
<br />developers of a lower river recovery implementation pro-
<br />gram waits in the distant future. Nonetheless, genetic
<br />and demographic conditions of the native resources are
<br />inarguably worse today than a decade or two ago, and cer-
<br />tainly they are worse than at the time of target species' re-
<br />spective listings as endangered. Further deterioration
<br />seems inevitable unless innovative management scenar-
<br />ios are developed and implemented in the near term.
<br />We offer a practical plan for management of lower
<br />Colorado River native fishes that is biologically sound, fis-
<br />cally responsible, and considerate of potentially conflict-
<br />ing resource uses. The plan incorporates state-of-the-art
<br />information from conservation genetics and population
<br />dynamics arenas and offers a realistic mechanism by
<br />which to ensure the continued presence of healthy pop-
<br />ulations of native fishes in the lower river ecosystem.
<br />Proactive decisions and fund allocations by bureaucrats,
<br />coupled with aggressive implementation by fisheries man-
<br />agers, are all that is required to realize the full benefits of
<br />the plan. What may well be missing is the political will to
<br />carry it out.
<br />Acknowledgments
<br />The US Fish and Wildlife Service, Region 2, convened a
<br />scientific work group (SWG) in 1999 to draft a plan for
<br />management of endangered fishes in the lower Colorado
<br />River. This article is one outcome of that process. The
<br />members, technical advisors, and support group of the
<br />SWG included the following people, in addition to the authors:
<br />from the US Bureau of Reclamation, Thomas Burke and
<br />Glen Gould; from the Nevada Department of Wildlife, Jon
<br />Sjoberg, Mark Warren, and Gene Weller; from the US Fish and
<br />Wildlife Service, Chester Figiel, Lesley Fitzpatrick, Owen
<br />Gorman, Stuart Leon, Cynthia Martinez, C. O. Minckley,
<br />Sam Spiller, Pete Stine, Manual Ulibarn, and Robert Williams;
<br />from the California Fish and Game Department, Chris Hayes;
<br />from the Arizona Game and Fish Department, Rob Bettaso,
<br />Tom Liles, and Kirk Young, and from the New Mexico De-
<br />partment of Game and Fish, David Propst.
<br />References cited
<br />Brower A, Reedy G Yelin-Kefer J. 2001. Consensus versus conservation in the
<br />upper Colorado River Basin Recovery Implementation Program.
<br />Conservation Biology 15:1001-1007.
<br />Carlson CA, Muth RT. 1989. The Colorado River: Lifeline of the American
<br />Southwest. Pages 220-239 in Dodge DP, ed. Proceedings of the Interna-
<br />tional Large Rivers Symposium, Canadian Journal of Fisheries and
<br />Aquatic Sciences 106 (special publication).
<br />Dowling TE, Minckley WL., Marsh PC, Goldstein ES. 1996a. Mitochondrial
<br />DNA variability in the endangered razorback sucker (Xymuchen texanus):
<br />Analysis of hatchery stocks and implications for captive propagation.
<br />Conservation Biology 10: 120-127.
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