Rescinding a 254-mm Minimum Length Limit on White Crappies at Ft. Supply Reservoir, Oklahoma: The Influence of Variable Recruitment, Compensatory Mortality, and Angler Dissatisfaction

Abstract

A 254-mm minimum length limit on crappies Pomoxis spp. was implemented on January 1, 1990, in Ft. Supply Reservoir, Oklahoma, to improve population size and age structure and angler catch rates but was rescinded 6 years later because of angler complaints. Before the regulation, the population was characterized by fast-growing and short-lived white crappies P. annularis; the spring fishery was supported by age-2 fish. Size structure fluctuated widely before the length limit was implemented, ranging from 1% to 40%, but stabilized after the length limit, exceeding 20% in 5 of the next 6 years. Age structure (percent age 3 and older) never exceeded 10% before the length limit, was greater than 10% the first 4 years after the length limit was imposed, and then declined to less than 10% in 1994–1995. Before the length limit, estimated conditional natural mortality was 45% and exploitation was 40%. Survival from age 1 to age 2 averaged 27% before the length limit and did not change substantially following its implementation. Abundance of quality-size (200–249 mm) and preferred-size (>250 mm) white crappies increased after the length limit was imposed. Angler catch rates increased following the regulation, but harvest rates were unchanged and harvest by number and yield declined. A Beverton–Holt equilibrium yield model, fitted using the pre-length-limit data, accurately predicted a reduction in yield. It was apparent from this study that typical fish population metrics are insufficient for managing a crappie fishery. Angler effort declined dramatically after the length limit was imposed, and vocal anglers registered their displeasure with their inability to harvest crappies. Reservoir-specific or lake-specific human dimensions data are also needed to properly assess angler desires before regulations are imposed. Managers should be flexible with regulations and be responsive to changing angler and fishery needs.