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effects of electrofishing on these species were similar to those of non-electrofishing <br />gears and that electrofishing was no more harmful than other gears. <br />INTRODUCTION <br />Electrofishing has been used extensively to sample fishes in the Upper Colorado <br />River Basin and its use has increased to monitor population status and trends of <br />endangered fishes in the basin (Osmundson and Burnham 1998; McAda 2002). <br />Although a practical and effective technique, electrofishing has received increased <br />scrutiny because of documented lethal or sub-lethal effects to individual fish (Sharber <br />and Carothers 1988; Dalbey et al. 1996). Snyder (1992, 1995) reviewed studies that <br />exposed injuries to individual fish and along with Nielsen (1998) recommended that its <br />use be curtailed or severely limited with endangered species. Electrofishing is usually <br />selected over other sampling gears in the Colorado River Basin because it is more <br />effective in fast, turbid waters. Schill and Beland (1995) argued that electrofishing is no <br />more harmful than other sampling gears and the most important implication is whether <br />electrofishing has population-level effects. Effective sampling is essential for obtaining <br />adequate data for research or to determine population status and all gear types have <br />the potential to cause injury, harm, or death to an individual animal. However, it is <br />critical that a sampling gear not cause population-level effects, especially with rare <br />species. <br />This study examined capture-recapture data for three endangered fish species <br />from the Upper Colorado River Basin with the objective of determining if the effects of <br />