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2000. No razorback sucker larvae or juveniles were identified during the project. Little change was observed in the composition of native and nonnative fishes among years, and little difference was observed between treatment and control reaches (Figure 12). Nonnative fish captures were lowest in 1998 and highest in 1999 in both the treatment and control reaches (Figure 13). Nonnative cyprinids grew and reproduced during the sampling period. ~ Changes in age structure (adults/subadults) were observed between trips each year. The numbers and relative abundance of subadults (<40 mm TL) tended to increase during the year in 1998 and 2000, but in 1999, the highest catch of subadults was observed on the first trip. The relative abundances of subadult ~ nonnative cyprinids likely were underestimated because seine mesh size was selected to exclude fish less than 25 mm. Although this assumption was not specifically evaluated, small fish were frequently observed to escape through the seine. However, sucker larvae greater than 20 mm were often captured. ~ In all years in the treatment reaches, numbers of adults (> 40 mm TL) declined on each trip until the final trip, which may indicate some short-lived impacts of removal on the adult population. In contrast, no consistent decline in adult NNC in the control reaches was observed (Figure 13). ~ Results of the ANCOVA comparisons of NNC CPE indicated a significant difference among years, removal trips, and river reaches (Table 4; Figure 14). Differences among years were attributed to the high CPE in 1999. Differences among removal trips reflected an overall upward trend in 1999 and , 2000. In treatment reaches, NNC CPE decreased on the first three trips in 1998 and 1999, but increased on the final trip. In control reaches, NNC CPE tended to increase on all trips in all years, except for trip 3 in 1999 (Figure 15). Nonnative CPE was not statistically different between treatment and control reaches, although the significant interaction effect between treatment and control reaches (reach'TC effect [Table 4]) suggested that CPE in control sections were sometimes greater than those in treatment sections within specific river reaches (Figure 16). Colorado pikeminnow CPE was higher in 2000 than in 1998 or 1999, but this difference was likely not statistically significant, and similar increases were observed in both treatment and control reaches (Figure 14). We examined NNC CPE in each of the two individual backwaters that were sampled on two consecutive trips in 1998 to test between-trip differences (Figure 17). In one backwater (RM 60.3), the ~ -13- 1