Exploitation of Northern Pike in Seven Small North-Central Minnesota Lakes

Abstract

Exploitation of native northern pike Esox lucius was studied in seven small (<300 ha) north-central Minnesota lakes in view of historical declines in northern pike sizes and heightened interest in experimental length limit regulations. Northern pike in the seven lakes had different population densities, size distributions, and exploitation rates. Creel surveys showed that anglers released 75% of the northern pike that they caught. Annual exploitation rates based on tag returns observed during a stratified creel survey ranged from 0.04 to 0.22 among the seven lakes. Good agreement was found between two methods for estimating annual exploitation in all but one lake. The size-selective nature of the recreational fishery was evident in annual exploitation rates. Annual exploitation rates for the larger northern pike (>500 mm total length) were approximately 2 to 9 times greater than for smaller fish (≤500 mm). Relatively high total annual mortality rates (mean = 0.48) compared to annual exploitation rates (mean = 0.10) indicated that natural mortality was an important aspect of northern pike population dynamics. Demands by anglers interested in catching larger fish and the high rates of catch-and-release observed in this study imply that success of experimental length limit regulations for northern pike should not be judged only by yields.