Exploitation of Largemouth Bass in Wheeler Reservoir, Alabama and Simulated Effects of Minimum Length Limit Regulations

Between the early and late 1990s, a nearly 10-fold decline in angler catch rates of large (?2.27 kg) largemouth bass (Micropterus salmoides) was observed in Wheeler Reservoir, Alabama. The objective of our study was to estimate the exploitation rate of largemouth bass and compare predicted population responses from simulated minimum length limit (MLL) regulations in an attempt to explain this reduction. Exploitation was seasonal, with most of the harvest occurring during spring. Spring and early summer exploitation estimates adjusted for tag loss and angler non-reporting ranged from 10% to 15% in 2001, 9% to 14% in 2002, and 6% to 10% in 2003. No fish were reported as harvested in the first four months following tagging in October 2002. Simulation modeling predicted that a 406-mm MLL could potentially increase by 56% the proportion of a cohort that would recruit to 508-mm (approximately 2.27 kg), compared to a 305-mm MLL. Thus, current exploitation rates and an angler enforced 305-mm MLL did not account for the dramatic decline of largemouth bass ?2.27 kg in Wheeler Reservoir. Additionally, nearly half as many fish were predicted to recruit to the more restrictive 406-mm MLL, compared to a 305-mm MLL. Our results have implications for largemouth bass management in reservoirs that have a substantial contingency of tournament anglers. Restrictive length limits have the potential to increase the abundance of trophy length fish in a population but at the cost of restricting the number of fish available for anglers to catch and weigh-in at a tournament.

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