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involving four personnel and two seines does not appear as substantial an effort considering the hundreds of miles of river, adjacent ponds, and flooded bottomlands that are infested with NNC. Perhaps there is potential to lengthen the 'window of opportunity' by increasing the frequency of removal in selected habitats, adjusting the timing of removal to include additional removal in the fall, or by using different methods or gear types, such as the electric seine being built and evaluated by Colorado State ~ University (Cameron Watford, personal communication). These methods should be explored along with more precise methods for evaluating native fish response to removal efforts. A response may be subtle and difficult to detect statistically with current ISMP methods, but nonetheless important to the i endangered fishes. 5.0 CONCLUSIONS Conclusions specific to our working hypotheses were: 1) Cyprinid removal by seining all backwaters in a river reach will deplete nonnative cyprinid abundance at a backwater level. • Green River ~ i. Depletion was observed within some individual backwaters within one-day sampling occasions. ii. No consistent or significant declines in catch or catch rate were observed in individual backwaters where fish were removed on consecutive removal trips. • Colorado River i. Depletion was observed within some individual backwaters within one-day sampling occasions. ii. Backwaters were seldom available to be seined more than one trip so the trip removal effect could not be evaluated. ~ 2) Cyprinid removal by seining all backwaters in a river reach will deplete cyprinid abundance of a reach leve% • Green River i. Significant differences were observed between treatment and control reaches in the ~ Green River, but no decline in catch rate in treatment areas was observed relative to catch in control areas. ii. Temporary reductions in abundance of nonnative adults were observed at a reach level in the Green River. iii. In five unique backwaters sampled on each trip, declines in combined catch and , catch rate were observed at a reach level in consecutive removal trips. -19- 1