Lake trout
Salvelinus namaycush(Walbaum, 1792)

member of the Salmon Family (Salmonidae)












What's In a Name?
Lake trout: named for the habitat in which it is found

Salvelinus (sal-veh-lynn´-us) taken from a word meaning "little salmon"
namaycush (nam´-ay-cush) a Native American name, translated as "tyrant of the lakes"


    Where Do They Live?
Lake trout in Minnesota live primarily in Lake Superior and many of the deep, cold lakes of St. Louis, Lake, and Cook counties. They also occur in a few lakes of the upper Mississippi River drainage. They were introduced to Grindstone Lake near Sandstone many years ago. Lake trout only do well in lakes where the water temperature does not exceed 18° C (65° F). They spend most of their time in the deep water where there is plenty of oxygen and no vegetation. Other species that occur in the same habitat include lake whitefish, bloaters, burbot, and deepwater sculpins.


How Big Do They Get?
How Long Do They Live?
In Lake Superior, lake trout reach 114.3cm (45 in) or more and can weigh over 18.2 kg (40 lbs). They are usually smaller in inland lakes, and even in Lake Superior you are most likely to catch lakers in the range of 450-650 mm (18-26 in) and about 1.4-2 kg (3-4.5 lbs). Minnesota's state record for lake trout is a whopping 19.7-kg (43 lbs 5 oz). It was caught from Lake Superior in Cook County. Lake trout commonly reach the ages of 12-16, but they can live for 25 years.

    What Do They Eat?
Young lake trout first eat a diet of copepods and waterfleas. Then add opossum shrimp. Adult trout eat mostly fish including ciscoes, bloaters, smelt, and cottids. Other things that have turned up in lake trout stomachs are freshwater sponges, both aquatic (water) and terrestrial (land) insects, shrews, and even yellow warblers.

What Eats Them?
Young lake trout are eaten by a variety of piscivorous (fish-eating) fishes. Adults have very few predators because they live in deep waters. Their major predator, besides humans, is the sea lamprey, which has contributed greatly to the decline of lake trout populations in the Great Lakes.


How Do They Reproduce?
Lake trout spawn in the fall, mostly in October though early November, when water temperature falls below 10° C (50° F). They spawn over boulder beds where water currents keep the rocks clear of silt. Lake trout do not dig nests, but the early arriving males clear away algae, slime, and any other debris by fanning the rocks with their fins and scraping them with their bodies. Males are not territorial and they do not fight over females. Spawning takes place over the rock as males press along side of females. Sometimes two males and one female are involved. Sometimes several males and females form a spawning group. Each fish will repeat the spawning act many times over a period of days or weeks. The fertilized eggs sink to the rock bottom and fall into the protective crevices. Here the current of the passing water keeps the eggs oxygenated and silt free. A single female may lay 2,000-20,000 eggs depending on her size. The embryos develop for 4 to 5 months and hatch into alevins (free swimming embryos) then in February and March. The alevins live in the rock crevices for another few weeks while they finish their fin development. Then they disperse into the lake.


Conservation and Management
Lake trout used to be a very important commercial fish in the Great Lakes. A combination of predation by the sea lamprey, declines in the cisco populations (their main food), and overfishing caused their populations to go way down. Today they are recovering in Lake Superior, but they probably will never return to their previous numbers. The lake now has exotic competitors, like coho and chinook salmon, as well as exotic forage fish like smelt and alewives. The ecosystem is a very different one from what it was when the lake trout was king.

"Cool Fact": For many years the Canadian and American governments have been working to control the sea lampreys in the Great Lakes. They do this by using poisons that selectively kill larval sea lampreys.




Permission is granted for the non-commercial educational or scientific use of the text and images on this Web document. Please credit the author or authors listed below.

Photographs by Konrad P. Schmidt
Text by Ted Halpern, Nicole Paulson,& Jay T. Hatch in cooperation with
the Minnesota Department of Natural Resources' MinnAqua Aquatic Program

This page developed with funds from the
MinnAqua Program (Minnesota Department of Natural Resources, Division of Fisheries)
and the
Sport Fish Restoration Program (Fish and Wildlife Service, US Department of the Interior)

Maintained by Jay T. Hatch
General College and James Ford Bell Museum of Natural History
University of Minnesota, Minneapolis/St. Paul

Last updated 23 October 2002