Using Electrofishing Catch Rates to Estimate the Density of Largemouth Bass

Abstract

Catch rates are commonly used to indirectly index population density, e.g., nighttime electrofishing to survey Largemouth Bass Micropterus salmoides populations. However, the relationship between catch rate and population density must be known in order for catch rate to serve as an accurate index. We sought to determine if Largemouth Bass electrofishing catch rate was linearly or nonlinearly correlated to population density in high density populations using measurement-error models and Monte Carlo simulations. Previous studies of the relationship between Largemouth Bass electrofishing catch rate and density have occurred in low-density populations (<50/ha). We hypothesized that high-density Largemouth Bass populations may result in gear saturation during electrofishing sampling, i.e., too many fish for dipnetters to capture resulting in missed captures. This would therefore underrepresent the population's density. The nighttime electrofishing catch rate of 66–294 Largemouth Bass/h was linearly related to their population density (77–152/ha) over 15 experimental events. The linear relationship suggests electrofishing catch rate is an appropriate index of population density in similar high-density Largemouth Bass populations.

Received August 11, 2014; accepted December 3, 2014

ACKNOWLEDGMENTS

We thank staff of the North Platte and Kearney Nebraska Game and Parks Commission, and the University of Nebraska Kearney for help in the field and laboratory, especially J. Kreitman, C. Huber, J. Lorensen, B. Newcomb, B. Eifert, B. Peterson, R. Alberts, N. Munter, J. Munter, C. Uphoff, D. Schumann, and M. Cavallaro. This project was funded by the Nebraska Game and Parks Commission through Federal Aid in Sport Fish Restoration, Project F-190-R.