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<br />ured to traverse diagonally from pool to pool create a maximum riffle gradient <br />of 1.3 percent. This maintains maximum riffle velocities below 3.5 ft/s <br />(Kubitschek and Medford 1997). This type of structure is more natural than the <br />fish passageway constructed at the Redlands Diversion Dam in 1996 on the Gunnison <br />River. Unlike the fish passageway at Redlands Diversion Dam on the Gunnison <br />River, the GVIC passage structure does not have a trapping facility to allow <br />researchers to definitively determine the number and types of species using the <br />passageway. <br /> <br />The Recovery Implementation Program (RIP) is pursuing fish passage at two <br />other diversion dams on the Upper Colorado River upstream of the GVIC Diversion <br />Dam to allow endangered fi sh uni mpeded movement to hi stori c stream reaches <br />upstream. Providing passage at GVIC will only extend the range of endangered <br />fishes upstream about 3 miles to Price-Stubb Dam. However, providing passage at <br />both Price-Stubb and Government Highline Diversion dams will potentially open up <br />an additional 50 miles of historic habitat upstream. <br /> <br />Purpose and Objectives <br /> <br />The purpose of this investigation was to evaluate whether sub-adult and <br />adult Colorado pikeminnow and other native and nonnative fishes would move <br />upstream through the passage structure at the GVIC Diversion Dam. <br /> <br />Specific objectives were to: <br /> <br />1. determine if sub-adult and adult Colorado pikeminnow and other native <br />and nonnative fishes would move upstream via the passage structure, <br />with emphasis on upstream movement of native species during low flows, <br /> <br />2. determine the extent of movement of sub-adult and adult Colorado <br />pikeminnow in the immediate vicinity of the GVIC Diversion Dam, with <br />emphasis on movement upstream past the diversion dam, and <br /> <br />3. determine the utility of using the type of fish passage structure <br />constructed at GVIC as a recovery tool for Colorado pikeminnow and <br />razorback sucker at other i nstream barri ers in the Upper Colorado <br />River Basin. <br /> <br />Anticipated end products from this evaluation included: <br /> <br />1. data on passage--number of species; numbers per species from <br />recaptured, marked fish, <br /> <br />2. data on temporal and spatial movement and distribution of transmitter- <br />tagged Colorado pikeminnow upstream, downstream, and in the immediate <br />vicinity of the diversion dam, and <br /> <br />3. numbers and species of nonnative fish removed from the river. <br /> <br />3 <br />