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<br />End Products <br /> <br />1. Data on passage--number of species; numbers per species from <br />recaptured, tagged fish. <br /> <br />2. Data on temporal and spatial movement and distribution of <br />radiotagged Colorado squawfish upstream, downstream, and in the <br />immediate vicinity of the diversion dam. <br /> <br />3. Numbers and species of nonnative fish removed from the river. <br /> <br />V. Study area: Upper Colorado Riyer from the Price Stubb Dam (river mile <br />188.3) downstream to Lorna (river mile 152.6); Lower Gunnison River-- <br />river mile 3.0-0.7; GVIC canal system--Palisade to Grand Junction. <br /> <br />VI. Study Methods/Approach <br /> <br />A two-year biological study is planned following construction of fish <br />passage at GVIC Diversion Dam to evaluate if fish will move upstream <br />through the passage structure. Field efforts for this evaluation will <br />rely on two separate techniques, both applied independently to <br />determine if sub-adult and adult fish will use the passageway to pass <br />over the GVIC Diversion Dam (river mile 185.1). The first method will <br />involve mark and recapture efforts in the immediate vicinity of the <br />diversion dam using electrofishing. Sub-adults and adults of the most <br />common large-sized, native fishes, flannelmouth sucker, bluehead <br />sucker. and roundtail chub, will be captured and PIT tagged. Plans are <br />to PIT tag approximately 1,000 fish from these three species. Attempts <br />will be made to PIT tag the number of flannelmouth, bluehead, and <br />roundtail to closely approximate the relative percentage that each <br />species comprises the population in the 15-mile reach of the Upper <br />Colorado River. Other common sub-adult and adult nonnative fishes such <br />as common carp and white sucker that are captured will be marked with <br />external, individually numbered Floy tags. <br /> <br />Other nonnative fishes such as centrarchids (largemouth bass, green <br />sunfish, etc.). ictalurids (channel catfish, black bullhead), and <br />esocids (northern pi ke) that are captured as "by-catch" wi 11 be removed <br />and disposed. The reason for removing these introduced fish is that <br />they are suspected of adversely affecting the native mainstem fishes of <br />the Colorado River basin in some fashion. Warmwater gamefish, such as <br />centrarchids, ictalurids, and esocids, are listed as frequent <br />contributors to the decline of native fishes and are thought to have <br />the greatest adverse effect on endangered native fishes. An increasing <br />body of evidence characterizes the negative interactions of nonnative <br />fishes with the endangered big river fishes (Hawkins and Nesler 1991; <br />Minckleyet al. 1991; Maddux et al. 1993; Lentsch et al. 1996). Some <br />of this evidence is indirect that includes inferences from field data <br />or results from laboratory studies of predation by nonnatives on <br />natives. Laboratory studies have documented agonistic behavior. <br />resource sharing, and vulnerability to predation (Papoulias and <br />Minckley 1990; Karp and Tyus 1990; Ruppert et al. 1993; Johnson et al. <br /> <br />4 <br />