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The Lake Trout
Nature Bulletin No. 553-A   Febraury 8, 1975
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Until thirty years ago, the Lake Trout was the choice food fish as well as the most highly prized game fish in the Great Lakes. Before that time, commercial fishermen caught and marketed millions of pounds of them from lakes Huron, Michigan, and Superior. This fish practically disappeared from the first two and, was decreasing rapidly in Lake Superior. They were never plentiful in Lake Erie.

This disaster was due almost entirely to the depredations of the parasitic sea lamprey which, about 40 years ago, bypassed Niagara Falls through the Welland Canal and spread slowly into the upper Great Lakes. The lake trout is its principal victim. (See Nature Bulletin No. 106, March 8, 1947 -- The Lamprey). After many years of effort, a joint research program by Canada and the United States has found ways to control that pest which has allowed a comeback of this magnificent fish along with other members of the Salmon family that have been stocked.

The lake trout -- called Mackinaw Trout in Canada -- is the largest of the trout. Great Lakes fishermen using nets have captured a few weighing over 100 pounds. In the Chicago markets they usually range from 2 to 10 pounds. It is a fish of cool deep freshwater lakes. In Lake Superior it is often taken at depths as great as 800 feet. Like other kinds of trout, it cannot endure warm water and spends most of its life where the temperatures are between 40 and 50 degrees Fahrenheit -deep in summer, shallower in cool weather.

The native home of the lake trout is in Canada, Alaska, and our northern states from Maine to Minnesota. In modern times, man has successfully introduced it into large deep lakes of California, the Pacific Northwest, Bolivia, Peru, and New Zealand.

In autumn -- usually late October -- the adults come into shallow water and spawn over a gravel or rock bottom. A group of males may join forces to clean off a common spawning area but the sexes do not pair off, no nest is built, and there is no parental care after the eggs are laid. Lake trout eggs are among the largest fish eggs known -- about one-fifth of an inch in diameter, pale amber in color, and translucent. A 24-pound female may lay 15, 000 eggs, a small number compared with most kinds of fishes. They develop very slowly and, in late February or March, hatch out fry with large inky black eyes and a huge yolk sac. They are transparent enough that the heart can be seen beating inside.

To avoid heavy losses from enemies and unfavorable conditions during the prolonged egg stage, they are often held in hatcheries. Eggs are stripped from "ripe" females, fertilized by milt from males, and allowed to develop in jars of cold running spring water. After hatching, they are sometimes reared to fingerling size, on a diet of ground meat, and then released.

In the wild, the first food of the young is small aquatic animals. Later, it feeds voraciously on other fish, especially herring, and almost any animal food, large or small. Among the strange items which have been found in their stomachs are an open jackknife, tin cans, rags, raw potatoes, ham bones, corncobs, and a watch and chain. In captivity they have lived as long as 24 years.

Anglers usually troll for lake trout with wire lines and spoons in deep water. In spring, when they are found in shallow water, some are taken by fly casting or with live bait. The record fish taken on rod and reel was 47-1/2 inches long, weighed 63 pounds, and was caught in 1930 in Manitoba, Canada.

The hybrid between a speckled and a lake trout is a "splake.

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