A comparison of electrofishing methods and fyke netting to produce reliable abundance and size metrics

Because different fishing gears may introduce different degrees of bias, we set out to compare two active sampling methods (alternating current (AC) and pulsed direct current (DC) boat electrofishing) and one passive method (modified fyke netting) in sampling sportfish in a midwestern US reservoir. Currently, the Illinois Department of Natural Resources uses AC electrofishing to sample reservoirs but a switch to DC is underway. Understanding how this switch will impact fisheries data is critical for future management decisions. We found catch per unit effort (CPUE) for all sportfish combined was greater (p < 0.0001) with AC electrofishing than DC electrofishing. Though not significant, largemouth bass (Micropterus salmoides) were sampled at a higher rate using DC electrofishing. Channel catfish (Ictalurus punctatus, p = 0.0494) and sunfish (Lepomis spp., p < 0.0001) were sampled at a significantly higher rate with AC electrofishing. We found a positive relationship between AC and DC electrofishing CPUE for largemouth bass (r ² = 0.702); however, no relationship between AC electrofishing and DC electrofishing was found for sunfish CPUE. Length frequency distributions of sunfish were significantly different for each gear used. The lack of a relationship between AC and DC electrofishing CPUE for sunfish species suggests data from future DC electrofishing may not be comparable to historical data obtained from AC electrofishing.