Within the Crown of the Continent, lake trout (Salvelinus namaycush) are a native species to Waterton and St. Mary lakes. After being introduced to the Flathead Lake in 1905, lake trout eventually migrated upstream and so far have colonized nine of the fifteen lakes that contain native bull trout on the west side of Glacier National Park.
Lake trout inhabit very deep, cold lakes and spawn in the fall on rocky substrates found in shallow water. Young lake trout feed on plankton and aquatic invertebrates. As they grow larger, they switch to a fish diet. In lakes that lake trout have colonized, native fish, such as the threatened bull trout, are slowly being replaced as the dominant aquatic predator. Once lake trout inhabit a lake, bull trout populations generally cannot be sustained.
Lake trout were discovered for the first time in Glacier’s Quartz Lake in 2005. Efforts are ongoing to evaluate the long term feasibility of removing lake trout from Quartz Lake, and potentially Logging Lake, to protect the park’s native fisheries.