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sucker comprised 59% of samples and smallmouth bass were 2.5% (Wick et al. 1985; Anderson 2002; 2005). A population explosion by smallmouth bass in the Yampa River began about 2001 (Anderson 2002; 2005), when smallmouth bass comprised 67% of seine samples and native fishes (roundtail chub only) were 1.4% of samples. In four years of sampling similar areas from 2003 to 2006, native fishes were 1% or less of the fish community in samples collected in riverine habitat (Bestgen et al., Yampa River Native fish response evaluation, RIP project 140). Native fish abundance was higher in isolated pools where smallmouth bass abundance was lower. Increased abundance of native fishes in seine samples in the period 2005-2006 may be due to a number of factors. This is discussed further below. Presence and severity of turbidity events in the Green River may also be an explanation for the relatively high variability in abundance of native fishes observed in seine samples collected from 2002-2004 compared to 2005-2006 (Bestgen et al. 2006, in part). We observed relatively high native fish abundance in seine samples in summer 2002 when no severe turbidity events were observed. Alternatively, in 2003 and 2004 we observed low native fish abundance in summer and two severe turbidity events occurred in each year. Similar to 2002, higher relative abundance of native fish in 2005 and 2006 was also associated with absence of extreme turbidity events. High turbidity may cause fish to lose orientation and be transported downstream. This hypothesis was supported by high catch rates of fish in drift net samples in the Green River in 2003 and 2004 after flood events (Fig. 43, in Bestgen et al. 2006). This also occurred in the Yampa River, when Colorado pikeminnow (and other taxa) abundance in drift samples typically increased when turbidity events occurred (Bestgen et al. 1998). Because such events in the Green River happened after native fish reproduction occurred, no additional larvae were available for re-colonization and their abundance remained low through autumn. Non- native fish were likely similarly reduced by turbidity events (e.g., red shiner and sand shiner in Whirlpool Canyon, summer 2003) but, because many of those taxa spawn into late-summer, populations could recover by autumn to achieve high population levels we observed. Fish 22