Evaluation of the Standardized Electrofishing Project for the Upper Colorado River Endangered Fish Recovery Program

The Upper Colorado River Endangered Fish Recovery Program has established standardized electrofishing to monitor Program progress. During August 2014, five boats and four rafts (units) were brought to Grand Junction, Colorado, to evaluate standardization. All boats used two 23-cm-diameter spheres as anodes and the hull as cathode; rafts used one 23-cm sphere and two sets of three droppers as cathodes. Each unit was assigned three 0.8-km reaches on the nearby Colorado River. All units used 60-Hz pulsed DC at 20% duty cycle and initially set current according to standardization, making adjustments as needed thereafter. Twenty-three species and 505 fish were caught with species per reach ranging from 2 to 10 and fish per reach 2 to 36. There were no significant differences in CPUE of species or fish per reach among units (P > 0.05). Only two species were sufficiently abundant to extend statistical analysis: Flannelmouth Sucker Catostomus latipinnis (241) and Bluehead Sucker Catostomus discobolus (104). One-way ANOVA of CPUE per reach for both species gave non-significant results (P > 0.05). We concluded that the standardized protocol achieved comparability among the units tested but large variance in catch data will require valid sampling methods to detect real population trends.