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Bestgen et al. 2006). Upstream reaches of Lodore Canyon now have a mix of sizes, including small fish, as reproduction has been noted throughout the canyon and upstream. In Whirlpool Canyon, modal size was lower than upstream and fish in the 151 to 200-mm TL size class or smaller were most abundant (Christopherson et al. 2005; Bestgen et al. 2006). Large numbers of fish, including smallmouth bass, in drift net samples in the Green River upstream of the Yampa River in 2003 and 2004 associated with turbidity events suggested susceptibility to displacement. Such displacement likely also occurred in the Green River downstream of the Yampa River because the Yampa contributed only about 25% of the flow downstream of the confluence during those events. The literature also suggested negative effects of flow increases on early life stages of smallmouth bass (Lukas and Orth 1995, Peterson and Kwak 1999, references therein); Winemiller and Taylor (1982) documented negative effects of turbidity and high flows on disruption of smallmouth bass spawning, nest destruction, and displacement of young. Increased flows levels via dam releases or turbidity events may be a potential controlling mechanisms for early life stages of smallmouth bass in this portion of the river. We believe that displacement or direct mortality of early life stages of smallmouth bass by flow or turbidity events, as noted in 2004 drift net samples, reduced survival of those age-0 fish and subsequently reduced abundance of the same year class of age-1 smallmouth bass in Lodore and Whirlpool canyons in 2005 (Fig. 16). Inexplicable abundance reductions in 2005 were also noted by Christopherson et al. (2005, M. Fuller conducted sampling in The Whirlpool reach), who conducted abundance estimates for smallmouth bass associated with removal efforts in 2004 and 2005 in the Green River in Whirlpool Canyon. They could not explain the reduction in smallmouth bass abundance in 2004 from 8,000 compared to about 3,300 fish in 2005, a decline of 59%, because they only had 31 % removal rate in 2004. Importantly, that decline did not account for recruitment of abundant smaller bass into the 2005 population, which is usually ample enough to replace the bass removed in the subsequent year: age-1 smallmouth bass were about 41 % of the population sampled in 2004. Christoperson et al. (2005) correctly surmised that a large portion of the difference in abundance in 2004 and 2005 was due to low recruitment 28