Reproduction of Lake Trout in Algonquin Park, Ontario

Abstract

In lakes of Algonquin Park, Ontario, lake trout (Salvelinus namaycush namaycush) spawn on clean, wave swept shoals of broken rubble ranging from 1 1/2 to 4 inches in diameter and in water from 6 inches to 12 feet deep. Weather conditions may influence the time and duration of the reproductive period but it most often occurs in the last half of October and lasts about 10 days. Water surface temperatures are usually between 50 and 55°F. Spawning occurs chiefly at night from sunset to about 10:30 p. m. Nightly counts were made of the fish on the beds during spawning in Lake Louisa in 1947. Courtship behaviour is described. Males made up 60–85 percent of the spawning population. The size composition of the spawning population varied markedly from lake to lake because of different growth rates. The smaller trout spawn first. Egg frequency estimates on the spawning beds averaged 50 per square foot. Saprolegnia infection of the eggs on the beds appears to be the main cause of egg mortality. Northern brown bullhead (Ameiurus nebulosus) and Menominee whitefish (Prosopium cylindraceum quadrilaterale) were the chief egg predators. Water level drawdowns in late fall and winter may expose some eggs and make large areas of potential beds unavailable for spawning. Time of hatching ranges from mid-February to late March, an incubation period of 15 to 21 weeks. The fry leave the spawning beds by at least mid-May.