Changes in Walleye (Stizostedion vitreum vitreum) Population in Rainy Lake and Factors in Abundance, 1924–75

Abstract

Annual commercial harvests of walleye (Stizostedion vitreum vitreum) from Rainy Lake steadily declined from 150,000 kg in the 1920s to 19,000 in the early 1970s; total (all species) harvests averaged 374,000 kg from 1924 to 1975, 45% greater than the MEI estimated allowable harvest. The walleye catch per unit of effort from commercial 102 mm gill nets declined from 43.63 kg/km in 1948 to 18.43 in 1969. Growth rate of walleye increased from 1959 to 1965, probably as a compensatory response to decreased abundance. The increased growth rate, in conjunction with heavy exploitation, caused the mean age of the walleye commercial catch to decline from 1957 to 1967. Both spring water levels and brood stock abundance were significant factors in walleye abundance 5 yr later. From multiple linear regression analysis, these two variables accounted for 65% of the variation in commercial walleye CUE. Key words: Percidae, Stizostedion, walleye, population dynamics, abundance, yield, exploitation, water level, Rainy Lake, Ontario–Minnesota