Optimal Stocking Densities of Walleye Fingerlings in Minnesota Lakes

Abstract

A generalized additive model was developed that described the effects of fingerling stocking density on the abundance of walleyes Sander vitreus in 551 lakes in Minnesota. Walleye abundance was measured as a catch per effort (CPE) from 1,511 standard Minnesota Department of Natural Resources gill-net assessments conducted during 1986–2004. In addition to fingerling stocking, the effects of lake morphometry, productivity, and fish community variables on walleye CPE were also described using a generalized additive model. Lake morphometry variables had sharply nonlinear effects on walleye abundance. Walleye abundance declined in lakes with areas less than 1,000 acres and increased rapidly in lakes with depths of less than 30 ft. The lake productivity variable, total alkalinity, was positively related to walleye abundance. Abundance of northern pike Esox lucius had a negative effect and abundance of yellow perch Perca flavescens a positive effect on walleye abundance. The response of walleye abundance to fingerling stocking was asymptotic: peak walleye abundance occurred at stocking densities greater than 0.65 lb·littoral acre⁻¹·year⁻¹. A fingerling stocking density of 0.50 lb·littoral acre⁻¹·year⁻¹ is recommended as a balance between increased abundance and relative costs of stocking for most lakes in Minnesota.