Exploitation of Walleye (Stizostedion vitreum vitreum) in Lac Des Mille Lacs, Northern Ontario, by Commercial and Sport Fisheries, 1958–75

Abstract

Harvests by three types of gear from Lac des Mille Lacs showed considerable differences in size selection of walleye (Stizostedion vitreum vitreum). Angling gear was most selective for smaller walleye (primarily 4–6 years old) and commercial gill nets and trap nets were most selective for larger walleye (primarily 5–11 years old), indicating there was not effective competition for fish of the same size. The great difference in size selectivity of the gears should serve as a caution against basing inferences about the status of stocks based on harvest from a single or similar gear.From 1971 to 1975 the total annual harvest (5.24 kg/ha) exceeded the theoretical potential yield (3.91 kg/ha) by 34%.The large number of age-groups (1–12), the high sport fishery catch per unit of effort (0.40 fish per man-hour) and the lack of appreciable change in rate of growth suggested no inimical effects on the walleye fishery due to exploitation.Walleye accounted for 62% of the total harvest (1971–75) reflecting both the preference for this species and their vulnerability to conventional (passive) commercial gear. The sport fishery harvest for the same period accounted for 92% of the total harvest. Key words: Percidae, exploitation, Stizostedion, gear selectivity