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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
THE LAKE TROUT
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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Update: June 2012
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