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Montana Field Guide

Montana Field Guides

Lake Trout - Salvelinus namaycush

Species of Concern
Native Species

Global Rank: G5
State Rank: S2
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
The Native Lake trout is currently ranked "S2" in Montana because it is at risk due to very limited and/or potentially declining population numbers, range and/or habitat, making it vulnerable to extirpation in the state. This species is a glacial relic in Montana known from native (never-stocked) populations occurring in Waterton Lake, Glenns Lake, Cosley Lake, and St. Mary Lake in Glacier National Park and Lower St. Mary Lake on the Blackfeet Indian Reservation, as well as a couple of small populations in the upper Missouri River basin. Otherwise, all other populations in the state are introduced.
General Description
The Lake Trout is a char of the same genus as Bull Trout and Brook Trout. Lake Trout are native in the St. Mary and Missouri River drainages and have been introduced to a few other scattered mountain lakes, Flathead Lake, and Fort Peck Reservoir. Lake Trout are a major game fish in much of Canada and were at one time a staple of the Great Lakes fishery. In Montana, the Lake Trout of Flathead Lake have achieved trophy status, growing to 42 pounds. Lake Trout inhabit very deep, cold lakes, living in water up to 200 feet deep. They spawn in the fall on the rocky substrate of the shoreline. They scatter or broadcast their spawn, a rarity in the trout group. Small Lake Trout feed on plankton and aquatic invertebrates but fish over 2 to 3 pounds eat a fish diet. Lake Trout are a highly-prized food fish in Canada and are catching on as a game fish in Montana with the advent of downriggers, electronic fish finders, and other specialized techniques.

For a comprehensive review of the ecology, conservation status, threats, and management of this and other Montana fish species of concern, please see Montana Chapter of the American Fisheries Society Species of Concern Status Reviews.

Diagnostic Characteristics
Lake trout are typically trout-like in shape. Like other chars, lake trout have light spotting on a dark background that can range from light green to almost black. A narrow, sometimes indistinct, white anterior border is present on the pectoral, pelvic and anal fins. Lake trout can be distinguished from other chars by their deeply forked tail

Species Range
Montana Range

All Ranges
(Click legend blocks to view individual ranges)

Range Comments
Lake trout are native to northern North America, with their historic range determined primarily by the extent and dynamics of the Pleistocene glaciations. The lake trout's native range includes portions of all of the Canadian provinces except Newfoundland and Prince Edward Island, and the states of Alaska, Maine, Illinois, Indiana, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New York, Ohio, Pennsylvania, Vermont and Wisconsin. Native Montana Populations are found within the Big Hole and Red Rock Drainages and the Hudson Bay Drainages of Glacier Park.

Observations in Montana Natural Heritage Program Database
Number of Observations: 276

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Deep, cold lakes and reservoirs (Montana Department of Fish, Wildlife, and Parks 2003). Deep cold water lakes and reservoir with some rocky bottom and on abundance of forage fish. Spawns over rocky shoal areas in lakes in depths from 10 to 120 feet.

Food Habits
Young lake trout feed on plankton and aquatic invertebrates. Diet is largely other fish after reaching 2-3 lbs. in weight.

Whereas lake trout can be found in cold rivers and shallow lakes in the northern portion of its range (Scott and Crossman 1973), in Montana native lake trout inhabit a few relatively deep, cold lakes remaining from the Pleistocene glaciations.

Reproductive Characteristics
Broadcasts spawn Oct-Nov. Eggs hatch in following March or April when water temperatures reach 34-38 degrees F. Fry soon move into deep water. No parental care.

The genetic uniqueness and significance of Montana's native lake trout populations to the post-glacial distribution of the species mandate that these remnant native populations be conserved.

Threats or Limiting Factors
Lake trout populations have been decimated by over-harvest, habitat loss, pollution, and introductions of non-native fish species, especially sea lampreys (Petromyzon marinus) into the Great Lakes. Efforts to re-establish native lake trout populations have generally not met management goals.

  • Additional ReferencesLegend:   View Online Publication
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    • Cox, B.S. 2010. Assessment of an invasive Lake Trout population in Swan Lake, Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 79 p.
    • Dux, A.M. 2005. Distribution and population characteristics of lake trout in Lake McDonald, Glacier National Park: Implications for suppression. M.Sc. Thesis. Bozeman, MT: Montana State University. 87 p.
    • Mullins, M.S. 1991. Biology and predator use of cisco (Coregonus artedi) in Fort Peck Reservoir, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 68 p.
    • Nelson, P.H. 1953. Life history and management of the American Grayling (Thymallus signifer tricolor) in Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 45 p.
    • Owens, R.W., and R.A. Bergstedt. 1994. Response of slimy sculpins to predation by juvenile lake trout in southern Lake Ontario. Transactions - American Fisheries Society. 123(1): 28-36.
    • Poore, M.D. 1973. The fishery resource of Mystic Lake, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 30 p.
    • Rahrer, J.F. 1963. Age and growth of four species of fish, Flathead Lake, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 16 p.
    • Syslo, J.M. 2010. Demography of Lake Trout in relation to population suppression in Yellowstone Lake, Yellowstone National Park. M.Sc. Thesis. Bozeman, Montana: Montana State University. 104 p.
    • Tennant, L.B. 2010. Spawning and early life-history characteristics of Bull Trout in a headwater-lake ecosystem. M.Sc. Thesis. Bozeman, MT: Montana State University. 67 p.
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Citation for data on this website:
Lake Trout — Salvelinus namaycush.  Montana Field Guide.  .  Retrieved on , from