Lake trout (Salvelinus namaycush) are native to Canada, Alaska, the Great Lakes, New England, and parts of Montana. Lake trout were intentionally stocked in Lewis and Shoshone lakes in 1890 by the U.S. Fish Commission (a predecessor of today's US Fish and Wildlife Service). The species was first documented in Yellowstone Lake in 1994 and evidence from chemical patterns in the ear bones of lake trout captured in the late 1990s indicate that they were introduced illegally from a nearby lake some time in the 1980s. Despite major efforts to remove them by gillnetting, the lake trout are having a significant ecological impact on the native Yellowstone cutthroat trout, an important food for other native animals. Lake trout differ from cutthroat trout as potential prey because they can grow larger, occupy deeper areas of the lake, and spawn in the lake instead of shallow tributaries.
Cutthroat trout comprise about 80% of a mature lake trout's diet. Biologists estimate 41 cutthroat trout are saved each year for every mature lake trout caught. Learn More: Lake Trout Information Continued...
Nonnative lake trout in Yellowstone Lake threaten the survival of native Yellowstone cutthroat trout and species that depend on it.
With continued aggressive control efforts, fisheries managers expect to reduce lake trout numbers and lessen impacts to cutthroat trout. Recent monitoring indicates Yellowstone cutthroat trout in Yellowstone Lake are starting to rebound and the lake trout population is in decline.