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Colorado pikeminnow nursery areas are. Non-native species were found in lower densities in Westwater Canyon than above or below the canyon - again a function of canyon habitat availability. Non-native densities were negatively correlated with the peak flow at the State Line gage. The analysis of chub recruitment was based on a comparison of cohort (as determined by length frequency analysis) densities (electrofishing CPE) relative from year to year. From this analysis, it appeared the 1994 cohort recruited the best; the 1993 cohort the worst. YOY produced in 1994, although not particularly abundant, had grown larger (45 mm TL by mid-August) than either the 1992 or 1993 cohorts. In addition, overwinter flows for the 1994 YOY cohort were lower and more stable than experienced by the other two cohorts. Survival of all juvenile chubs (> 100 mm TL) appeared to be high, although not quantified. The humpback chub population in Westwater Canyon was monitored at three sites established for the Interagency Standardized Monitoring Program (ISMP): Miner's Cabin (RK 199.9 - 198.6), Cougar Bar (RK 194.4 - 193.6), and Hades bar (RK 192.2 - 191.8). Densities of adult humpback chub, as referenced by trammel net CPE (fish / 23 m net hour), fluctuated greatly from trip to trip but overall remained fairly stable -with the trend in CPE slightly up at Miner's Cabin and slightly down at the other two. The same data for roundtail chub indicated a relatively strong downward trend at all sites. Lincoln- Peterson population estimates, although compromised by large 95% confidence intervals, showed a similar trend in population size for the two species. LIST OF KEY WORDS Colorado River, Westwater Canyon, humpback chub, roundtail chub, reproduction, recruitment, monitoring, population estimates, flow recommendations xii