Frequency of Strong Year-Classes: Implications on Fishery Dynamics for Three Life History Strategies of Fishes

Abstract

Many studies have examined variation in year-class strength and associated density-dependent growth of fishes. Few studies, however, have considered the effects of these factors on fishery quality. We examined how the frequency of strong year-classes affects fish harvest and size structure for three species with varying life histories. We modeled both random and systematic occurrences of strong year-classes for white bass Morone chrysops (short-lived species), largemouth bass Micropterus salmoides (species with intermediate longevity), and blue catfish Ictalurus furcatus (long-lived species). For white bass and largemouth bass, intermediate frequencies of strong year-classes (i.e., every 3–10 years) incrementally reduced harvest but improved the proportional size distribution (PSD) under current fishing regulations. The greatest improvements in PSD with minimal effects on harvest (relative to annual strong year-classes) occurred when strong year-classes were produced every 3 years for white bass and every 5 years for largemouth bass. In contrast, production of strong blue catfish year-classes every 6 years maximized harvest and resulted in a fivefold increase in PSD relative to a strong year-class frequency of every 1–2 years. Greater annual consistency in harvest and PSD for fishes with intermediate and high longevity was achieved when strong year-classes occurred systematically rather than at random. Our results suggest that intermediate frequencies of strong year-class production, relative to species longevity, serve to balance harvest and size structure characteristics. The use of fish stocking or water level manipulations to systematically produce strong year-classes can also improve the consistency of annual harvest and size structure for longer-lived fishes (>10 years).

Received March 28, 2012; accepted August 27, 2012

ACKNOWLEDGMENTS

We thank P. Michaletz and R. Schultz for providing white bass length-at-age data and J. Schlechte for providing valuable input for model development. Constructive comments on earlier versions of this manuscript were given by A. Barkoh, R. Betsill, K. Bodine, D. Buckmeier, M. Driscoll, J. Schlechte, and M. Quist. Funding for this project was provided through Federal Aid in Sport Fish Restoration Program Grant F-22-D to the Texas Parks and Wildlife Department, Inland Fisheries Division.