Efficacy of largemouth bass stock enhancement in achieving fishery management objectives in Florida

Abstract

Stock enhancement is a practiced management strategy for sustaining and rebuilding largemouth bass fisheries in Florida and throughout their native and introduced range. However, quantitative assessment comparing efficacy of stocking to traditional management approaches are rare. We adapt an age-structured population model that explicitly represents the size and density-dependent effects on mortality and somatic growth to assess potential outcomes of stocking largemouth bass relative to traditional length-based harvest regulations. We explore two management situations in which stocking might be considered: maintaining high abundance in an exploited population and rebuilding a population that has been depleted. We find that different stocking scenarios comprised of combinations of size, density, and duration at which fish were stocked influence three fishery response metrics: abundance of catchable fish, abundance of trophy-sized fish and relative wild spawner biomass. Stocking larger juveniles can bypass some of the compensatory density dependence and yield a net augmentation of total abundance of catchable largemouth bass, but usually leads to a reduction in the abundance of the wild population and the number of trophy-sized bass. We find enhancements of small (25 mm) fingerlings fail to help maintain or augment wild populations, but could be effective at rebuilding depleted bass populations and may replace the need for effort restriction. Our study suggests stocking is a comparatively powerful tool for achieving high catch rates in largemouth bass fisheries, but may perform poorly at meeting other objectives of largemouth bass management such as production of trophy fish.