The lake trout is the largest trout native to the Great Lakes. This fish strongly prefers a water temperature of 45-55 degrees. Thus, while lake trout may be found in shallow water only 10 to 15 feet deep in spring and fall, it follows these frigid water temperatures to depths of 100 to 200 feet in the summer and winter. Although it seems to have a feeding preference for ciscoes, it also concentrates on alewives, smelt or sculpin, and sometimes takes crustaceans, insects and other fish.
Many lake trout seem to return each fall to use the same spawning beds, although some don’t show this homing behavior. The eggs are deposited after dark, often on shoals. Young lake trout become sexually mature at 6 or 7 years of age. The average adult weighs in at 9 – 10 pounds but some individuals weigh up to 50 pounds. The life-span of the lake trout may exceed 25 years.
Parasitization by sea lampreys severely reduced the lake trout populations in Lake Michigan to near-extinction from 1935 to 1965. Chemical contaminants and over-fishing pressures have also contributed to the problem. However, the invaluable lake trout is coming back. Today, lake trout are avidly sought after by both commercial and sport anglers, but enjoyed mostly for the sport.