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<br />-71 <br />0000 1 <br /> <br />I. PURPOSE AND NEED <br /> <br />A. General. The Colorado River and its tributaries provide water for municipal <br />use, irrigated agriculture, industry, and mining (Bishop 1971). Bishop <br />emphasizes that these various uses of water have resulted in conflicts. <br />Water development in the Upper. Colorado' River Basin altered the natural <br />river ecosystem (Miller et ale 1982; Wydoski 1980). Dam construction and <br />storage of water to serve human needs changed the natural hydrograph through <br />dam operations that released water for the irrigation season (Johnson 1974) <br />or for generating power during peak use periods. Changes in the hydrograph <br />have, in turn, altered aquatic habitats, particularly backwater and <br />floodplain habitats that are vital to the early life stages of native <br />fi shes. Co 1 dwater releases from dams have reduced water temperatures of the <br />natural and historic warmwater aquatic ecosystem. Water quality has been <br />impacted from toxic heavy metals through mining activities and from <br />increased selenium concentrations through irrigated agriculture. Nonnative <br />fish species were introduced in the rivers and ~anmade reservoirs, both <br />Intentional and accidental introductions of nonnative fish species have <br />changed the composition of the natural fish community. <br /> <br />Human alteration of the Upper Colorado River Basin (Figure 1) has resulted <br />in four endemic fishes (razorback sucker, Xvrauchen texanus; bony tail, Gila <br />eleqans; humpback chub, Gila ~; and Colorado squawfish, Ptvchocheilus <br />1 uci us) bei ng 1 i sted as lIendangeredll under the Endangered Speci es Act. <br />Although numerous factors have contributed to listing these native fishes <br />as endangered, several factors appear to be particularly important. Habitat <br />alteration and introduction of nonnative fish species were considered to be <br />the most important factors in the extinction of 40 native North American <br />fishes (27 species and 13 subspecies) during the past century (Miller et ale <br />1989) . These two factors undoubtedly contributed to the demise of the <br />endangered Colorado River fishes. <br /> <br />B. Purpose. Endangered fishes in the Upper Colorado River Basin have been and <br />continue to be impacted by a number of factors including water depletions, <br />disrupted natural hydrograph through the operation of dams for irrigation <br />and hydro-power, losses of riverine backwaters and floodplain habitat from <br />altered streamflows, barriers to native fish migration, and predation by and <br />competition from nonnative fish species. Various recovery actions have been <br />taken to resolve water depletions, streamflow patterns, migration barriers <br />to fish by dams, and rehabilitation or restoration of floodplain habitat. <br /> <br />In 1996, the Recovery Implementation Program for Endangered Fishes in the <br />Upper Colorado River Basin (Recovery Program) developed a strategic plan to <br />control nonnative fish species. Recovery Program participants, representing <br />various interests, were directly involved in the development of the <br />strategic plan to control nonnative fish species that is summarized by Tyus <br />and Saunders (1996). <br /> <br />Nonnative fishes compose 76% of the fish species (42 of 55 species) in the <br />riverine enVironment of the Upper Colorado River Basin (Tyus et ale 1982). <br />These nonnative fishes constitute most of the fish numbers (96.7 - 99.6%) <br />found in backwater habitats in the Upper Basin (Cranney 1994; McAda et ale <br /> <br />1 <br />