The Effects of Different Intensities of Fishing on the Whitefish Populations of Two Alberta Lakes

Abstract

Two Alberta lakes, Wabamun and Pigeon, of about the same size and general nature have been fished for whitefish since 1918. After several yrs. of unusually heavy yields Lake Wabamun was closed during 1942 and 1943. Fishing began again in 1944 and has continued to date. Pigeon Lake was subjected to heavy fishing in 1941 and has continued to yield about twice its previous annual yields. Samples of the whitefish have been taken throughout the period 1942-1946 and analyzed for age composition and rate of growth. The whitefish of Lake Wabamun, which was closed for two years, show no change in growth rate and an increase in average age. The whitefish of Pigeon Lake, subjected to heavy fishing, show accelerated growth rate and decreased average age. The increase in growth rate compensates for the decreased average age so that a 100 fish of the present catch weigh 12 percent more than 100 fish of the 1942 catch. A further increase in efficiency may be expected when all the fish are growing at the rate of the youngest year classes now present. Along with increased growth rate and diminished average age in Pigeon Lake, there has been a decrease in the age of spawning fish. Thus, although younger fish are caught, the spawning escapement has not altered appreciably.