Estimating Harvestable Largemouth Bass Abundance in a Reservoir with an Electrofishing Catch Depletion Technique

Abstract

We developed a Leslie catch depletion method that uses electrofishing gear to estimate the abundance of harvestable (≥251 mm total length) largemouth bass Micropterus salmoides. In March-April 1992 and 1993, 10 coves, ranging in surface area from 2.3 to 3.7 ha, in Lake Guntersville, Alabama, were enclosed with a block net. and largemouth bass were removed during four to seven 1-h collection periods. Catch per effort regressed against cumulative catch declined linearly over time in all coves. Density ranged from 6 to 143 fish/ha and biomass ranged from 3 to 112 kg/ha. In two coves, larger fish were caught during initial collection periods, which dictated regression of catch per effort for weight against cumulative weight caught. Catchability was constant over time and was not affected by day versus night electrofishing or by the time interval (≤16 h) between collection runs. Coefficients of determination for regressions between catch per effort of subharvestable (≤250 mm TL) largemouth bass and cumulative catch of these fish were highly variable and appeared to co-vary with the biomass of harvestable largemouth bass. This catch depletion method provides a less expensive and potentially more realistic assessment of largemouth bass populations in spring than cove rotenone sampling conducted during summer and allows live release of fish.