Latitudinal Comparisons of Walleye Growth in North America and Factors Influencing Growth of Walleyes in Kansas Reservoirs

Abstract

We compared the growth of walleyes Stizostedion vitreum in Kansas to that of other populations throughout North America and determined the effects of the abundance of gizzard shad Dorosoma cepedianum and temperature on the growth of walleyes in Kansas reservoirs. Age was estimated from scales and otoliths collected from walleyes (N = 2,072) sampled with gill nets from eight Kansas reservoirs during fall in 1991-1999. Age-0 gizzard shad abundance was indexed based on summer seining information, and temperature data were obtained from the National Oceanic and Atmospheric Administration. Parameter estimates of von Bertalanffy growth models indicated that the growth of walleyes in Kansas was more similar to that of southern latitude populations (e.g., Mississippi and Texas) than to that of northern (e.g., Manitoba, Minnesota and South Dakota) or middle latitude (e.g., Colorado and Iowa) populations. Northern and middle latitude populations had lower mean back-calculated lengths at age 1, lower growth coefficients, and greater longevity than southern and Kansas populations. A relative growth index (RGI; (L _t /L _s) × 100, where L _t is the observed length at age and L _s is the age-specific standard length derived from a pooled von Bertalanffy growth model) and standardized percentile values (percentile values of mean back-calculated lengths at age) indicated that the growth of walleyes in Kansas was above average compared with that of other populations in North America. The annual growth increments of Kansas walleyes were more variable among years than among reservoirs. The growth increments of age-0 and age-1 walleyes were positively related to the catch rates of gizzard shad smaller than 80 mm, whereas the growth of age-2 and age-3 walleyes was inversely related to mean summer air temperature. Our results provide a framework for comparing North American walleye populations, and our proposed RGI provides a simple, easily interpreted index of growth.