An age-structured model for erratic crappie fisheries

White crappie Pomoxis annularis and black crappie P. nigromaculatus are important freshwater sportfishes in North America. Because of erratic recruitment (the number of fish that survive to age 1 each year) fishery yields are inconsistent. We developed a simple age-structured model to help manage crappie fisheries. The model changes population biomass by age-specific somatic growth, and population abundance through recruitment and age-specific natural and fishing mortalities. Using empirical stock-recruitment data and a stochastic component to simulate the effects of abiotic environmental fluctuations on recruitment, the model simulated empirical recruitment dynamics of a crappie population over 30 years in a large impoundment. Effects of density-dependent growth and natural mortality were modeled, but did not substantially affect the yield given the observed magnitude of recruitment fluctuations. Model predictions of population biomass and yield tended to be high relative to empirical estimates, but not unrealistic. Erratic recruitment of crappie populations has made development of management strategies elusive. This model should help fishery managers examine potential management alternatives. (C) 1998 Elsevier Science B.V. All rights reserved.