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Relative abundance of the 1992, 1993, and 1994 cohorts is graphically presented in Figure 12. Data tracking each cohort from Age 0 through their third growing season (Age 2+) is depicted. Age 0 densities refer to late summer seine haul information. Age 1+ and Age 2+ densities refer to electrofishing data. Obviously, Age 0 and Age 1 and 2 CPEs are not directly comparable (seine catch vs electrofishing). Therefore the intention is to compare the relative abundance of similar age groups between cohorts. In this analysis, the 1992 Age 0 cohort was the strongest and the 1994 Age 0 cohort was the weakest. However, the 1994 Age l+ cohort was better represented in electrofishing samples than the other two cohorts. By the time the cohorts were in their third growing season, the 1992 cohort was collected at a rate of 0.34 fish / hr, the 1994 cohorts was collected at a rate of 0.28 fish/hr and the 1993 cohort at 0.19. Catch rates of the 1992 and 1993 cohort increased through time (Age 1 to Age 2) which suggests either; a. differential sampling efficiency (larger fish are more susceptible to electrofishing) and / or b. immigration of juvenile chubs into the study area. The 1995 cohort, as discussed in the YOY catch analysis, was simply non-existent, which was substantiated in the 1996 J electrofishing sampling (refer to Appendix Table 4). Survival of the 1996 cohort, the strongest of the five YOY cohorts studied, was beyond the scope of the present study. Late Juvenile and Adult Monitoring The late juvenile and adult fish community was sampled on twelve occasions throughout the five year study. The overwhelming majority of effort was expended in the upper canyon (upstream of the major rapids in Westwater Canyon), i.e., between RK 199.2 and 190.4. Humpback chubs were collected on every occasion at every site sampled in the upper canyon. On two occasions, sampling occurred in the lower canyon (below the rapids) at RK 182.9 in April of 1992 and at RK 186.4 in 7uly of the same year. Humpback chub were not collected in the lower canyon and roundtail chubs were collected in lower numbers than upstream. In support of this apparent lack of adults, YOY CPEs were significantly less from this area of the canyon than both above and within the canyon. For these reasons, subsequent to July 1992, sampling was concentrated in the upper canyon. Native species dominated the collections of larger sized fish, both along the shorelines (electrofishing and hoop netting) and in the main channel (trammel netting). Native chubs accounted for 57.4% and 71.4% of the electrofishing and hoop net catch, respectively, with the overwhelming majority of those fishes collected electrofishing (Figures I3). Roundtail chubs were the most abundant species collected at the Miner's Cabin site, but were outnumbered by unidentified juvenile chubs at the lower two. Main channel habitats were sampled with trammel nets. More effort was expended on this technique than any other and it produced 57.3% of our total catch (N=3992). Native chubs dominated the trammel net catch; humpback chubs accounted for 28.6% of the total catch, roundtail chubs were the most abundant species accounting for 37.3%, and unidentified chubs comprised 6.4% all sites combined (Figure 14). Again, roundtail chubs were the most numerous species collected throughout the study at each of the three intensively sampled sites followed closely by humpback chubs. Juvenile Gila spp. and other unidentified adult chubs were more abundant at the two lower sites but did not comprise more than 10 % of the total trammel net catch at any location. Humpback chub trammel net catch rates are graphically presented for each trip and each sampling location in Figure 15. The trend in humpback chub catch rates seemed erratic throughout the study but basically fluctuated around the following site means: RK 198.6 = .40; RK 194.4 = .47; and RK 192 = .32. A regression analysis of these CPES against the sampling date (the 1992 b and d trips were used in the analysis) indicated a positive trend at RK 198.6 (RZ = .5726; p=.08) and a slight downward trend at the other sites: RK 194.4 (RZ = -.125; p=.74) and RK 192 (RZ = -.196; p=.5 87). Taking into account the probability values, densities of humpback chub increased at Miner's Cabin and changed very little elsewhere throughout the course of this five year study. In Figure 15, the July, 1994 and 1996, 16