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Habitat variation Differences in catch rates between run and riffle habitats were assessed for species that likely serve as forage for Colorado pikeminnow; these were bluehead sucker, flannelmouth sucker, roundtail chub, white sucker (including white sucker x native sucker hybrids), and salmonids (brown trout, rainbow trout, and mountain whitefish combined). No comparisons were made within Stratum 1, where no riffles were present within the three sample reaches. On a river-wide basis, catch rates of bluehead and flannelmouth suckers, the two most abundant species, were significantly higher (T-K, P < 0.05) in riffles than in runs (Figure 9). In downstream strata 2-6, where bluehead suckers made up a large majority of forage-size fish, very few were captured from run habitats. In the two uppermost Colorado River strata (strata 10 and 11), catch rates within runs and riffles were nearly the same. The capture rate in riffles of the Gunnison River stratum was especially high. Bluehead sucker catch rates in riffles were significantly higher (P < 0.05) than in runs only in strata 5-9 and 12. For flannelmouth suckers, the difference in catch rate between the two habitat types was not as pronounced as for bluehead suckers. The mean catch rate in riffles appeared to be higher than in runs in nearly all strata; only in uppermost Stratum 11, were catch rates in runs apparently higher than in riffles. However, within individual strata, no differences were statistically significant (P > 0.05). For roundtail chub, capture rates in upstream strata 7-12 were similar both among strata and between riffles and runs within strata. Catch rates in Stratum 11 appeared to be higher in runs than in riffles but the difference was not significant (P < 0.05). In downstream strata 1-6 capture rates were very low in both habitat types (Figure 10). White suckers displayed a pattern similar to roundtail chub: few captures in either habitat type in the lower strata and little difference in capture rates between habitat types in upstream strata 7-10 and Stratum 12. Only in Stratum 11 was the capture rate in runs significantly different (higher) than in riffles (Figure 10). Salmonids were common only in uppermost Stratum 11; capture rates there were significantly higher (P < 0.05) in riffles than in runs (Figure 10). Body Condition of Native Fish Spatial Variation Relative body condition generally increased in an upstream direction for each of the three primary native species (Figure 11). In the Gunnison River stratum, mean condition of each species was significantly (P < 0.05) higher than in any Colorado River stratum group. Within the Colorado River stratum groups, results from pairwise comparisons were varied. For bluehead sucker, mean relative condition within each stratum group was significantly higher than in all more downstream stratum groups. This was also the case with flannelmouth suckers, with the exception that the two most downstream stratum groups were not significantly different from one another. For roundtail chub, sufficient data were only available for the two upstream stratum groups; these were not significantly different (P > 0.05). Length weight regression coefficients for the three primary native species are provided in Table 1. 18