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EXECUTTVE SUMMARY <br />We evaluated aspects of the protocol offered by Stanford et al. (1996) for restoration of <br />biota in regulated rivers. The chronology of river regulation events and associated biotic <br />evaluations that occurred in the regulated reach of the Green River upstream of the Yampa River <br />from 1962 to 1996 offered an opportunity to determine the effectiveness of thermal enhancement <br />and discharge re-regulation to restore native fishes. Prior to closure of Flaming Gorge Dam, the <br />Green River supported an intact native fish assemblage and few non-native fishes. Closure and <br />operation of Flaming Gorge Dam eliminated most native fishes in the regulated reach of the <br />Green River from 1967 to 1978 because low water temperatures inhibited reproduction. The <br />annual hydrograph exhibited no spring peak and high summer base flow, and sediment load was <br />reduced. Thermal enhancement of the regulated reach via dam penstock modification in 1978, <br />immediately restored reproduction by most common native fishes in Lodore Canyon, a 32-km <br />section of the Green River upstream of the Yampa River. Reproduction by rare Colorado <br />pikeminnow and razorback sucker was not detected. <br />Discharge re-regulation begun in 1992 partially restored spring peaks and lowered early <br />summer base flows. Electrofishing conducted from 1994 to 1996 demonstrated that native fishes <br />were numerically dominant in Lodore Canyon. Prevalence of cold water fishes in Lodore <br />Canyon declined since 1980, and abundance of cool or warm-water fishes increased. Sampling <br />also indicated increased abundance of adult Colorado pikeminnow in Lodore Canyon since 1980 <br />and individuals were detected in spring, summer, and autumn. Length changes of recaptured fish <br />and length-weight relationships indicated high growth rates. Lodore Canyon maybe an <br />important feeding habitat for adult Colorado pikeminnow. Drift net sampling did not detect <br />reproduction by that species. Increased abundance of Colorado pikeminnow in Lodore Canyon <br />since 1980 maybe from flow re-regulation, additional summer warming, or individuals <br />dispersing from expanding populations elsewhere in the basin. Roundtail chub and razorback <br />sucker were rare and may be declining in abundance. Populations of other native fishes appeared <br />stable. <br />iv <br />