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2002 to 2004 study period also had a more stable, albeit slightly higher than historical, summer- <br />winter base flow pattern because power generation fluctuations at Flaming Gorge Dam were <br />minimized. In Lodore Canyon, drought in 2002 to 2004 resulted in low base flows, and thermal <br />regimes in the study area were more similar to those in the pre-dam era than during any other <br />post-impoundment period. This ensured a close match of Green and Yampa River water <br />temperatures during drought years when Colorado pikeminnow larvae were drifting downstream <br />from the Yampa River in summer. <br />Green River peak flows in Whirlpool Canyon in the pre-impoundment period showed a <br />typical dome-shaped hydrograph, with low late-summer, autumn, winter, and early-spring base <br />flows, rising to a peak in late spring and early summer. Post-impoundment Green River peak <br />flows in Whirlpool Canyon were lower and arrived earlier than historically, an effect of Flaming <br />Gorge Dam. Whirlpool Canyon flow peaks during 2002 and 2004 were lower than the historical <br />average while the 2003 peak flow exceeded the average historical condition (1946 to 1962). <br />Base flows in Whirlpool Canyon in the 2002 to 2004 period matched the historical average <br />pattern reasonably closely. Thermal regimes in 2002 to 2004 were similar to historical ones <br />because dam-related cooling was probably overwhelmed by enhanced warming during low <br />flows. <br />We used raft-based electrofishing gear, seines, drift nets, and trammel nets to sample <br />Green River fishes from Browns Park downstream to Island-Rainbow Park. When data <br />obtained with all gears were combined, native fishes in the 2002 to 2004 period comprised only <br />10.3% of total catch and non-natives were 89.3%; the remaining 0.4% were hybrids. Fish <br />species richness was lowest in upstream reaches and cold-water or cool-water tolerant species <br />were more abundant in electrofishing samples. Predominant taxa included brown trout, white <br />sucker, fathead minnow, and mountain whitefish. Species richness was higher in downstream <br />v