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Drift net sampling detected reproduction by Colorado pikeminnow in Lodore Canyon in <br />2006, along with a possible razorback sucker. Reproduction by Colorado pikeminnow was not <br />noted in other years. Drift net sampling revealed that fish, including early life stages of <br />smallmouth bass, were displaced in response to turbidity and higher flow events in 2003 and <br />particularly, 2004. <br />We were able to link displacement of smallmouth bass in 2004 in the Green River with <br />reduced year-class strength and population abundance in 2005. The abundance reduction was <br />documented in this study with catch-effort statistics. The decline was also observed in a study <br />designed to remove smallmouth bass from the Green River downstream of the Yampa River, <br />where a 58% reduction in abundance was observed from 2004 to 2005. Only a portion of the <br />reduction was due to removal. Sampling and length-frequency histograms indicated a near <br />complete failure of the 2004 year class as age-1 fish in 2005, an age group that made up about <br />40% of the population sampled by electrofishing in 2004. Reductions of this magnitude are <br />rarely observed or persist in removal studies between years. These data suggested that flow <br />manipulations from Flaming Gorge Dam may be useful to disadvantage survival and recruitment <br />by early life stages of smallmouth bass. Additional information is needed on smallmouth bass <br />early life history to understand when flow manipulations may be most useful. Effects of flow <br />fluctuations on native fishes should also be considered. <br />Colorado pikeminnow continued to use Lodore Canyon heavily in summer in 2002 to <br />2006, based on captures we made and those in a concurrent companion study. Ripe male <br />Colorado pikeminnow were detected there in 2001 and 2003, which in concert with detection of <br />larvae in 2006, indicates conditions suitable for reproduction in some years. <br />Based on our 2002 to 2006 sampling, the net effect ofnon-native fish predators and flow <br />and temperature regimes on the native fish community, was mixed. During this study, we were <br />vii <br />