Angler Catch Rates and Factors Affecting Growth of Walleye in Escanaba Lake, Vilas County, Wisconsin

Abstract

Walleye (Stizostedion vitreum vitreum) is the most sought after sport fish in northern Wisconsin with licensed anglers. Management of such an important natural resource is increasingly difficult, effective management of walleye fisheries needs to take into account the fundamental parameters of a fish population. The objectives of this study were to determine the factors influencing growth of walleye in Escanaba Lake, Vilas County, Wisconsin, and to determine if angler catch rates and catchability of adult walleye in Escanaba Lake vary with population density. Growth of walleyes was modeled as a function of density independent and density dependent variables in Escanaba Lake during 1980-1996. Von-Bertalanffy growth parameters (L∞, K, and t0) were estimated with nonlinear regression from the mean annual length-at-age of walleyes in spring, 1980-1996. The rate at which length approaches asymptotic length of walleye in Escanaba Lake was directly related to the number of growing degree-days in October of the previous year and inversely related to the abundance of age-0 walleyes in the previous year. Asymptotic length was inversely related to the number of growing degree-days in October of the previous year and directly related to abundance of age-0 walleye in the previous year. To increase growth of walleye in Escanaba Lake, angling regulations would need to increase prey abundance or increase the length of the growing season. Angler catch rates were modeled of adult walleye were modeled as a function of adult walleye density to determine if catchability of walleyes to angling was density dependent in Escanaba Lake during 1980-1995. Linear regression was used to describe the relationship between angler catch rates (number per 1,000 angler-hours) and catchability (q) of walleyes from a compulsory creel census and mark-recapture estimates of walleye abundance (number per acre). For walleye of all ages (3 and older), angler catch rate was directly related to population density, whereas catchability was unrelated to population density. For walleye of individual ages 3-8, angler catch rate was also positively related to population density. Catchability was also unrelated to population density for individual ages 3-4 and 6-8, but declined with population density for age 5. I conclude that the catchability of walleyes to angling in Escanaba Lake does not vary with population density, and therefore, that angling is self-regulating.