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juvenile/adult component of the population. Electrofishing data was specifically used for initial captures in the population estimate, length-frequency analysis and determining movement of Gila in ~ Westwater Canyon. Gila were identified to species using a suite of diagnostic characters (i.e., degree of frontal depression, presence of scales on nuchal hump, "angle of the dangle", etc.) in conjunction with the "art of seeing well" (Douglas et al. 1998). Information collected from all Gila spp. captures included ~ total length (mm), weight (g), sex (mature chubs; 1998 and 2000), and dorsal and anal fin ray counts. In addition, PIT tag numbers were recorded from recaptured chubs. Initial chub captures of fish greater than 150 mm received a PIT tag and the number was recorded. Information collected for all fish species caught included total and standard lengths (mm) and weight (g). Information collected for other endangered species captured included total and length (mm), weight (g), and PIT ~ tag number. Data Analysis Population Estimate ~ Population estimates were determined for adult humpback chub and roundtail chub (>200 mm) in Westwater Canyon using closed population models within Program CAPTURE (Otis et al. 1978, White et al. 1982, Rexstad and Burnham 1991). Program CAPTURE was used for model selection to help determine the most appropriate estimator but population estimates were routinely calculated using several estimators (Appendices I-II): M° (null estimator), Jackknife Mh, Darroch Mt, Chao f Mth, Chao Mt, and Chao Mh. A separate adult population estimate was calculated for each species in each year. Program CAPTURE was used to determine confidence intervals around the estimate, the coeffiecient of variation, and the probability of capture. Linear regression analyses were conducted on the resulting population estimates for the respective species to examine short-term trends in the populations throughout the period of this study. Confidence intervals were determined for all estimators. Profile likelihood intervals are provided in lieu of 95% confidence intervals for M° (null estimator) and the Darroch Mt. The profile likelihood interval helps to account for model selection uncertainty by providing wider confidence intervals (Appendix I; David R. Anderson and Gary C. White, Colorado State University, Ft. Collins, ~ Colorado personal communication). In addition, these intervals tend to give more correct confidence intervals for small samples (Ross Moore, Mathematics Department, Macquarie University, Sydney, Australia personal communication). All confidence intervals are provided for comparison among all estimators used to calculate population estimates in Westwater Canyon (Appendices I-II). CPUE Catch per unit effort (CPUE) was determined for trammel net effort toward the capture of humpback chub and roundtail chub through the period of this study. CPUE was compared between passes within and among years using the Kruskal-Wallis nonparametric ANOVA with Dunn's multiple comparisons test to examine the equality of samples and the two-sample Kolmogorov-Smirnov to ~ compare the distribution of catch rates. In addition, total annual CPUE comparisons were tested 3