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Logan, Utah), the null estimator (Mo) was used to determine the population estimates of adult humpback chub in Westwater Canyon, 1998-2000. The adult humpback chub population estimate was 4,744 individuals in 1998 (Table 1). The profile likelihood interval around this estimate was 3,760 - 14,665 (CV = 0.23; p-hat = 0.035). In 1999, the adult humpback chub population estimate decreased to 2,215 individuals (Table 1). The profile likelihood interval around this estimate was 1,608 - 7,508 (CV = 0.28) with a slightly higher ~ probability of capture (p-hat = 0.041). The adult humpback chub population estimate in 2000 remained approximately the same at 2,201 individuals (Table 1). The probability of capture also remained the same (p-hat = 0.041). However, the profile likelihood interval was tighter (1,335 - 4,124; CV = 0.28). The relationship among these three estimates indicates ashort-term decreasing trend in the Westwater Canyon adult humpback chub population (Figure 1). However, the slope of this short- term trend does not significantly depart from zero and each point estimate exceeded the minimum viable population identified in the recovery goals (USFWS 2002). . CPUE Total trammel net captures for humpback chub were 501 in 1998, 278 in 1999, and 277 in 2000 (Table 2). Total captures in 1998 included 486 adults, 12 of which were recaptured. An additional three subadult humpback chub were captured in trammel nets. In 1999, 267 adults were included in the total captures. Eight of these individuals were recaptured. subadult captures in the trammel nets r were once again three individuals. The total captures for 2000 included 261 adult humpback chub. Eleven of these were recaptured. subadult captures included in total trammel net captures for 2000 were slightly increased at five individuals. Mean catch per unit effort (CPUE) decreased across all passes from 1998 to 2000 (Figure 2). The ~ slope of this decreasing trend significantly departs from zero (p < 0.05). The Kruskal-Wallis test indicated there were no significant differences between passes within years, but there were significant differences (p < 0.05) between passes among years. The Kolmagorov-Smirnov test indicated there were no significant differences in the distribution of catch rates between passes within 1998 and 1999. However, there were significant differences (p < 0.05) between passes within ~ 2000 and among years. Comparisons of mean CPUE and the distribution of catch rates between years (all passes combined) indicated significant differences (p < 0.05) between all years. Length-Frequency ~ The length-frequency histograms for Westwater Canyon humpback chub indicated similar bimodal distributions for 1998 and 1999, with a majority of fish in the 240-280 mm and 310-350 mm size classes (Figure 3). In 2000, this distribution became trimodal, with the size classes being 230-260 mm, 280-310 mm, and 340-360 mm. The largest humpback chub caught in each year was 380 mm in 1998, 390 mm in 1999, and 410 mm in 2000 (Figure 3). ` 5