Montana Water Center - aquatic sciences lab

Aquatic Sciences Laboratory - Species Profiles

Lake Trout
Salvelinus namaycush

Lake trout have been introduced in Montana for recreational purposes, by both legal and illegal means, but relic native populations exist from the last glaciation period in Elk Lake, Twin Lakes, St. Mary Lake and Waterton Lake. They are a highly prized sportfish due in part to their tendency to fight hard, their voracious feeding habits, and good flavor. Additionally, lake trout are the largest of the char (current Montana state record is 42.5”, 42.69 lbs. from Flathead Lake in 2004) and the longest lived of any salmonid (reportedly up to 62 years).

Lake trout have a unique reproductive behavior in relation to other salmonids. Neither females nor males construct a redd or nest. Instead, mature lake trout congregate over rocky bottom areas, generally on windswept shores where fine sediment deposition is kept to a minimum. In most habitats, the rocky outcroppings chosen are in shallow waters, but instances of deep water spawning grounds have been noted. When a female is ready to spawn, a male comes along side to fertilize her eggs, which then fall into crevices among the rock outcroppings. Spawning generally occurs during the fall (October & November), with the fry emerging from the rocks in the spring (March or April).

While the loss of lake trout in the Great Lakes from invasion of sea lampreys and overexploitation by fishing has been seen as a tragedy, with extensive amounts of money and resources devoted to their restoration, Montana lake trout have become more of a pest. There are two prominent instances of the problem they pose. Lake trout were illegally introduced into Yellowstone National Park and since have become a dominant predator of Yellowstone cutthroat trout in Yellowstone Lake, adding more pressure to a population already threatened by whirling disease and competition/hybridization with introduced trout. In recent years, lake trout have begun to spread throughout waters of Glacier National Park, due in part to the introduction of mysis shrimp (a major prey of young lake trout), and have become a threat to native populations of bull trout, mainly through competition.

References:

Brown, C.J.D. 1971. Fishes of Montana. Big Sky Books, Bozeman, MT.
Behnke, R.J. 2002. Trout and Salmon of North America. The Free Press, New York.
Flavelle, L.S., M.S. Ridgway, T.A. Middel, and R.S. McKinley. 2002. Integration of acoustic telemetry and GIS to identify potential spawning areas for lake trout (Salvelinus namaycush). Hydrobiologia 483: 137-146.
Stapp, P. and G.D.Hayward. 2002. Effects of an introduced piscivore on native trout: insights from a demographic model. Biological Invasions 4: 299-316.

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