Effects of a maximum length limit on a slow-growing Largemouth Bass population

Abstract Objective Length-based regulations remain the primary approach to managing black bass Micropterus spp. However, effectiveness can vary depending on angler attitudes toward harvesting fish. Voluntary catch and release of legal-sized fish can render length limits ineffective, while the abuse of liberal length limits can lead to overexploitation of sport fish populations. Therefore, knowledge of angler attitudes paired with current information on population dynamics is important for effectively measuring the success of implemented regulations. In 2016, a 406-mm maximum length limit for Largemouth Bass M. nigricans was implemented statewide in Florida, United States. Concerns arose about how this regulation might affect slow-growing Largemouth Bass populations, particularly in mesohaline marshes, where fish tend to be smaller and shorter lived than those in freshwater habitats. Methods To evaluate the effect of this regulation, we compared angler attitudes and population dynamics before and after implementation on the Escambia River marsh. Relative abundance estimates from daytime electrofishing samples were used to quantify changes in population size between years. Year-class strength and total annual mortality were estimated from age data, and exploitation was estimated with high-reward tagging. Access-point creel surveys were conducted to determine fishing effort, catch rate, and angler attitudes toward Largemouth Bass harvest. Results Relative abundance estimates were similar from year to year, but total mortality increased and a shift in age structure occurred after the regulation was implemented. Creel survey estimates indicated high (≥30%) harvest rates yet low angler effort. Conclusions Although high harvest rates, increased total mortality, and a shift in age structure were observed, low angler effort and exploitation rates combined with similar abundance estimates suggest that the current level of harvest is not negatively affecting Largemouth Bass abundance.