Changes in fish populations over an 80-year period: Big Pine Lake, Wisconsin
From 1897 to 1977, landowners recorded sport catches for Big Pine Lake, a 256 hectare lake in northern Wisconsin that has experienced light fishing pressure. The species composition of the catch remained fairly stable for 40 years, from 1897 through 1940, with muskellunge Esox masquinongy, walleye Stizostedion vitreum vitreurm, and black bass (Micropterus spp.) all accounting for substantial fractions of the total. Northern pike Esox lucius were first recorded in 1946, apparently having entered after an outlet dam washed out in 1944. Subsequent increases in the proportion of northern pike coincided with declining percentages of muskellunge. By the 1950s, the relative abundance of walleye declined, ultimately almost to zero, while the percentage of bass more than doubled. This change began during the warmest decade on record. By 1977, the walleye population had rebounded, bass had declined to pre-1940 levels, northern pike were abundant, and muskellunge were relatively scarce. Long-term changes in summer temperatures and colonization by northern pike appear to have been important factors causing changes in species composition. Effects of human exploitation have been slight. Although the species composition changed dramatically over the 80 years, the only sustained change has been the substitution of northern pike for muskellunge.