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

Use of Angling Gear to Evaluate the Potential Benefits of Minimum Length Limits on a Highly Mobile Midwestern Blue Catfish Population

“…Our estimates of growth, the TL-weight relationship, and mortality for the Blue Catfish population in Mark Twain Lake were within the range of estimates reported for other reservoir populations. Values for asymptotic length (L ∞ = 1,017 mm) and the growth coefficient (K = 0.12) fell within the reported range of 534-1,440 mm for L ∞ and 0.06-0.26 for K (Mauck and Boxrucker 2004;Boxrucker and Kuklinski 2006;Holley et al 2009;Dorsey et al 2011;Daugherty and Smith 2012). However, growth…”

“…2009; Dorsey et al. 2011; Daugherty and Smith 2012). However, growth rates of individuals were highly variable, which appears to be characteristic of this species (Mauck and Boxrucker 2004; Hilling et al.…”

“…Variable year‐class strength is common among fish populations (Daugherty and Smith 2012) and can influence estimates of A (Miranda and Bettoli 2007). We pooled age composition data for Blue Catfish across the 7‐year study to reduce the effects of variable year‐class strength on estimating A , as recommended by Miranda and Bettoli (2007).…”

Modeled Walleye Regulation Outcomes in a Midwestern Reservoir with Varying Forage and Walleye Density

“…In combination with the new barrier, increased stocking led to the establishment and retention of several large year-classes of Walleye. Annual strong year-classes can drastically alter size distribution due to density-dependent growth (Daugherty and Smith 2012), and repeated stocking of Walleye in Ontario resulted in extremely high biomass and reduced growth (Kaufman et al 2009). Similarly, Walleye growth in Lake Erie declined during years of high abundance and strong year-classes MODELED WALLEYE REGULATION OUTCOMES IN A RESERVOIR (Hartman and Margraf 1992).…”