Age and Growth of Crappies in Alabama Reservoirs and Evaluation of the Statewide Minimum-Length-Limit

Abstract

Black Crappies Pomoxis nigromaculatus and White Crappies P. annularis in Alabama are currently regulated with a 229-mm minimum length limit (MLL) and a 30 fish/person/day bag limit. With the recent increased angler use of technologies that may allow anglers to target crappies more efficiently, evaluation of current regulations was warranted. We used electrofishing to collect 6,125 crappies between 2022 and 2024. We enumerated, measured morphometrics, sexed, and aged all fish. We estimated growth, mortality, and recruitment in all reservoirs and these data were variable among reservoirs. We developed reservoir-specific age-structured Beverton-Holt equilibrium yield models. We ran models using four MLLs to observe predicted population effects with multiple regulation scenarios, which included an assumed “no MLL.” Reservoirs characterized by fast growth and low conditional natural mortality had the most favorable tradeoff associated with a MLL that maximized yield, limited decreases in harvest, and increased the number of memorable sized crappies. In five reservoirs, we split up data collected from the upper riverine versus the lower, main lake sections to analyze differences in population data between sections. We found fish collected did not reach the same size in most upper sections, compared to the lower section, possibly indicating growth overfishing in upper sections of these reservoirs, but could also be caused by underlying factors such as variation in habitat, density dependence, species interactions, and sampling bias. These data will be useful for managers to evaluate multiple regulation scenarios among crappie populations in different reservoirs. These data, coupled with angler preferences, would be useful for evaluating the most favorable regulation(s) that also have a biological underpinning.