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EXECUTIVE SUMMARY <br />Colorado pikeminnow, Ptychocheilus lucius, humpback chub, Gila cypha, and <br />razorback sucker, Xyrauchen texanus, are endangered fishes that reside in the Upper <br />Colorado River Basin and are often captured by electrofishing for research or <br />management purposes. Because of increased evidence of electrofishing injuries in fish <br />and concerns about potential negative effects on populations there have been <br />recommendations to curtail its use on endangered fishes. The objective of this study <br />was to determine if the effects of electrofishing on these three species were similar to <br />the effects of other sampling gears. Two hypotheses tested whether 1) recapture rates <br />or 2) growth rates were similar for electrofishing and non-electrofishing gear types. <br />A database of endangered fish captures and recaptures between 1975 and 2000 <br />was compiled and used for all analyses. Recapture rate was calculated for fish that <br />were recaptured at least once. For all three species, recapture rates of fish initially <br />captured by electrofishing were similar to recapture rates of fish initially captured by <br />non-electrofishing gears. Differences in recapture rate, based on gear type, ranged <br />from 1.2% to 2.7% and except for Colorado pikeminnow the rates were not statistically <br />different. Although recapture rates for Colorado pikeminnow were statistically different <br />(P=0.04), the difference in rates was small (2.4%) and determined not biologically <br />meaningful. Mean monthly growth rate was calculated for fish for the first and second <br />growing season between initial capture and first recapture. Growth rates for each of the <br />three species were similar for fish initially captured by electrofishing or <br />non-electrofishing gears and not statistically different. These results indicate that <br />vi <br />