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<br />Figure 1. Sketch map of the lower Colorado River basin.
<br />crappies, sunfishes, and striped bass dominate in reservoirs.
<br />Common carp; red shiner; channel, bullhead, and flathead cat-
<br />fishes; live-bearers (mosquitofish and mollies); and African
<br />cichlids are in most river channels, backwaters, and reservoirs.
<br />Other species, such as smallmouth bass, are more localized.
<br />Most nonnatives are ecological generalists, widespread and
<br />competitive within their natural ranges, and predatory or
<br />omnivorous (Marsh acid Pac:ey2003).
<br />Historical perspectives on
<br />Colorado diver management
<br />Efforts to control the Colorado River began soon after the ar-
<br />rival of western Europeans. Levees, diversions, and other
<br />structures were built to reduce the impact of the flood and
<br />drought that plagued development. The river resisted until
<br />1935, when Hoover Dam was closed to form Lake Mead, a
<br />reservoir large enough to hold 2 years' average flow. Other
<br />dams followed; the total capacity of today's reservoirs is suf-
<br />ficient to store more than 4 years' flow.
<br />Only a few people were alarmed by these early changes (e.g.,
<br />Miller 1946). Serious controversy did not arise until the
<br />1960s, first over the effects of channel dredging on wildlife and
<br />sport fish, then over concern for the native biota (Miller
<br />1961, Minckley and Deacon 1968). Early researchers con-
<br />cluded that development had dramatically altered the system,
<br />and public pressure to prevent species' losses was growing. The
<br />Endangered Species Act (ESA) of 1973, together with other
<br />environmental legislation, inspired the evolution of a "con-
<br />servation industry"-state and federal biologists, consul-
<br />tants, and academic contractors-funded by the de-
<br />velopment community in response to the new rules.
<br />In principle, ESA decisions are based on the best
<br />biological information, but many issues relating to
<br />species' conservation are largely socioeconomic or
<br />political. Thus, factors other than biology influence
<br />most plans and projects, reducing benefits to the
<br />species of concern. The US Fish and Wildlife Service
<br />(USFWS), charged with enforcing ESA and pro-
<br />moting sport fishing, has difficulty balancing these
<br />conflicting demands. State agencies face the same
<br />dilemma. Moreover, state and federal conservation
<br />agencies are placed in a position of challenging the
<br />responsibilities of other agencies that deal with re-
<br />sources such as water and power-agencies that are
<br />better funded and have more political clout. Ac-
<br />commodating the political, socioeconomic, and bio-
<br />logical concerns of opposing constituencies and
<br />such powerful adversaries is challenging at best.
<br />As recovery efforts have expanded, confronta-
<br />tions have increased: conservationists versus devel-
<br />opers, sport fish managers versus native fish propo-
<br />nents, and special interest groups versus protected
<br />natural resources. Agency intransigence or failure to
<br />comply with legislative requirements has been met
<br />by litigation, especially by nongovernmental orga-
<br />nizations (NGOs). Legislative relief has been sought
<br />and granted, for example, in the form of less than fully pro-
<br />tected experimental populations, "reasonable and prudent al-
<br />ternatives" (RPA) to jeopardy opinions, and other exemptions
<br />that have amended the ESA. (A jeopardy opinion by
<br />USFWS is a determination that a federally funded project will
<br />adversely affect a listed species or its critical habitat. RPAs are
<br />mitigation actions intended to offset project impacts.) Pro-
<br />visions for habitat management plans (HMP) have appeared,
<br />under which nonfederal entities can develop and operate
<br />projects with a "take" of listed taxa permitted so long as
<br />species' existence is not jeopardized. The conservation industry
<br />has answered site-specific questions quickly in response to tithe
<br />constraints. But these data have not been analyzed to any con-
<br />siderable degree; the reports based on them have benefited nei-
<br />ther from peer review nor from the scrutiny afforded by
<br />publication in the open literature; and public availability of
<br />these reports has been short-term or nonexistent. The con-
<br />sequence is that major decisions are based on local and some-
<br />times hastily collected information, often broadly applied.
<br />The lead agency for all four big-river fishes is USFWS Re-
<br />gion 6, which has jurisdiction only upstream of Glen Canyon
<br />Dam. That office inherited a study program (1963-1980)
<br />originally stimulated by the poisoning of the Green River in
<br />Wyoming and Utah (Holden 1991), which led to the Colorado
<br />River Fishery Project (1979-1987), which was converted in
<br />1987 to a 15-year, $60 million Recovery Implementation
<br />Program (RIP; USFWS 1987). The RIP was designed to allow
<br />continued water development and use while simultaneously
<br />pursuing recovery of endangered fishes (Wydoski and Hamill
<br />220 BioScience • March 2003 /Vol. 53 No. 3
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