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1 <br />1 <br /> <br />1 <br />1 <br />1 <br /> <br />1 <br />1 <br />1 <br /> <br />1 <br /> <br /> <br />1 <br /> <br />flow and sediment withdrawal in the Yampa River, including a loss of backwater <br />nursery habitat. <br />The preceding demonstrations of system-wide changes following alteration <br />of natural flow and sediment regimens, emphasizes the futility of recommending <br />flows for an entire system using models developed for discrete stream reaches. <br />The consequent loss and alteration of downstream habitat and indigenous biota <br />would negate benefits from such water development. <br />Stream Flow/Fish Fauna <br />Regulation of the natural flow regimen of the Colorado River (Figure 1) <br />and introduction of non-native fishes, ha <br />fauna, and a concomitant proliferation of <br />phenomenon is most apparent in reservoirs <br />from dams. The Yampa River has yet to be <br />diversions, and regulated flows. Because <br />fauna is similar to 'Historic conditions. <br />s caused a dramatic decline of native <br />introduced forms. This basin-wide <br />and areas immediately downstream <br />converted into a system of dams,. <br />of this, composition of native fish <br />Fishes indigenous to the Yampa River evolved under a regimen of variable <br />flows; a system of floods and drought. Conversely, many of the fishes <br />recently introduced into the Green River system evolved under more mesic <br />conditions. Studies investigating effects of spring and late summer/fall <br />flows on abundance and growth of small fishes in the upper Green River system <br />suggest that the native fauna is well adapted to a regimen of fluctuating <br />annual flows. <br />Late summer-fall is a critical period for growth and survival of young <br />Colorado squawfish, and flows in the Green River system at this time are <br />historically and predictably low. Pucherelli et al. (19$8) found that <br />39 <br /> <br />