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pikeminnow were captured only on the fourth and final sampling trip (August 25-28); they ranged from 25 ~ to 42 mm TL, and were all YOY with the exception of two large adults >500 mm TL. In 2000, a total of 1,489 YOY Colorado pikeminnow were captured, distributed among all trips from July 17-August 17. Lengths ranged from 16 to 52 mm TL, with average lengths increasing through the sampling period ~ (Figure 11). Numbers of fish captured and effort (area seined) varied from year to year due to discharge, amount of available habitat, and sampling protocols (Tables 5 and 6). During four trips in 1998, the area ~ seined was 22,194 m2 in treatment areas, and 5,082 mz in control areas. During four trips in 1999, the area seined was 34,400 m2 in treatment areas and 4,548 m2 in control areas. During five trips in 2000, the area seined was 131,580 m2 in treatment areas, and 29,400 m2 in control areas. Effort in 1998 was ~ limited because sampling was discontinued in habitats with large numbers of sucker larvae in the first seine haul, as outlined in the methods. Incomplete records were kept of the habitats where sampling was discontinued. There are only three records indicating sampling was discontinued, but there were a few occurrences on each trip that were not recorded. In 2000, the low stable flows produced more available habitat than previous years. The number of fish captured varied substantially among years (Table 5). In the three years of the study, 219,709 fish were captured in both treatment and control reaches. Nonnative cyprinid captures were lowest in 1998, with only 13,740 fish removed; however, native fish captures were very high (9,138), primarily larval suckers (8,829). Nonnative cyprinid captures were highest in 1999, with 84,598 nonnative fish removed; however, 1999 also had the lowest number of native fish (316). A total of 47,653 nonnative fish were removed in 2000. The highest number of Colorado pikeminnow (1,210) was captured in 2000; other native fish captures totaled 1,150 including larval suckers (Table 5). Nonnative cyprinids comprised the overwhelming majority of all fish captured (Figure 12). No other nonnative species comprised more than 2.5% of the total catch in any single year. Percentages of nonnative fish in treatment reaches increased in 1999 and remained relatively high in 2000. The relatively high proportion of natives in 1998 was comprised of larval suckers, likely primarily native ~' species. Colorado pikeminnow juveniles comprised 0.2% of the total in 1998, 0.1 % in 1999, and 2.3% in -12-