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Seine samples also showed significant differences in fish abundance across seasons (Xz = 19.08, 2 df, p < 0.0001). Abundance was highest in autumn (2.47 fish/ 10 m2, 95% Cl = 2.12 to 2.90), intermediate in summer (1.83 fish/ 10 mz, 95% CI = 1.44 to 2.28), and lowest in spring (1.25 fish/10 m2, 95% CI = 0.92 to 1.70). Species richness in seine samples collected from 2002 to 2004 was high in summer (N = 25) and autumn (N = 26), and lower in spring (N = 23). Seine samples also showed significant differences in fish abundance across years (x2 = 8.05, 2 df, p = 0.0178). Abundance was highest in 2003 (2.17 fish/10 mz, 95% CI = 1.82 to 2.57), intermediate in 2002 (1.88 fish/10 mz, 95% CI = 1.54 to 2.30), and lowest in 2004 (1.31 fish/10 mz, 95% CI = 0.93 to 1.86). Species richness (including hybrid combinations) in seine samples collected in the 2002 to 2004 period was highest in 2003 (N = 28), intermediate in 2002 (N = 25), and lowest in 2004 (N = 23). Individual species patterns.-High variation and interactions noted in statistical analyses and the large influence of a few abundant non-native fishes prompted us to examine patterns of fish abundance at annual, seasonal, and reach scales for each native and several common non- native species in seine samples collected during 2002 to 2004. Abundance of common native fishes was highest in 2002, and in most years, highest in summer. For example, bluehead and flannelmouth sucker and speckled dace abundance was highest in 2002 in all reaches, and comparatively low in 2003 and 2004 (Fig. 36 and 37). Abundance in all years was relatively low in spring, high in summer, and low again by autumn, except for speckled dace in Browns Park, which was rare in all seasons. Each species was relatively common in Browns Park, increased in abundance in Lodore and Whirlpool canyons, and declined in abundance in Island-Rainbow Park. Roundtail chub was most abundant in 2002 but was absent in Browns Park, rare in Lodore Canyon, most common in Whirlpool Canyon, and low in Island-Rainbow Park. Most specimens were captured in summer, and in two cases, showed highest relative abundance then (Fig. 37). Mottled sculpin was most abundant in Lodore Canyon, less so in Browns Park, and uncommon in downstream reaches (Fig. 38). Seasonal abundance of mottled sculpin was highest in summer in Lodore Canyon, where we often found small individuals in shallow near shore runs over sand substrate or in macrophytes. Mountain whitefish showed a distinctly different distribution 41