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L <br />numbers of NNC adults (> 40 mm TL) declined on each trip until the final trip. No consistent decline in <br />~ adult NNC in the control reaches was observed (Figure 5). <br />Results of the ANCOVA comparing NNC CPE indicated significant differences among years and <br />between treatment and control reaches (Table 4). The three-year mean CPE in treatment and control <br />~ reaches was 8.87 and 13.71 fish/m2 (t-test, t = -2.82, df = 243, P = 0.005) respectively, although the <br />difference was observed primarily in 1998 and 1999 (Figure 6). In both the treatment and control <br />reaches, NNC CPE tended to increase from trip to trip in 1998, and was more variable in 1999 and 2000 <br />~ (Figure 7). <br />Effects of removal efforts within a group of five unique backwaters that were treated on each trip <br />and each year, and thus were treated more often than other habitats, were not significant (df = 98, F = <br />~ 1.95, P = 0.17; Figure 8). The CPE generally declined on the first few consecutive trips, but increased on <br />the final trip during 1998 and 2000. In 1998 at the smallest scale of removal (one-day sampling occasion) <br />we observed a depletion effect in the first four seine hauls (Figure 9). However, this effect was short-lived <br />as CPE tended to increase by the beginning of the next trip. This effect could not be examined in 1999 <br />and 2000 due to changes in sampling protocol. <br />Colorado pikeminnow CPE did not appear to vary among years (Figure 6). Trends in CPE in both <br /> <br /> <br />treatment and control reaches were similar and no differences were observed between treatment and <br />control reaches in 1998 through 2000. <br />Block Nets <br />Of the habitats that were blocked with nets, only two (School Bus and White washes) were <br />inundated for the entire study period. The third habitat, Red Wash, only had one week of inundation. <br />Inundation refers to the period when nets had water in front of and behind them, water levels were <br />~ shallow enough to allow for seining, and nets had not been breached or overtopped. Results were not <br />consistent in these two habitats. <br />Generally, the percentage of adult nonnative cyprinids was lower inside the blocked section than <br />~' outside. Percentage of adults inside the block nets in School Bus Wash averaged 31% compared to 49% <br />-10- <br />1 <br />