Since their introduction in the late 20th century, non-native lake trout have disrupted the delicate ecosystem of Yellowstone Lake in Wyoming. This vast, 132-square-mile lake—the largest within Yellowstone National Park—has witnessed profound ecological changes linked to the presence of these invasive fish.
Known by various names including mackinaw, togue, and lake char, the lake trout is not indigenous to Yellowstone Lake. Instead, it hails from regions such as Alaska, Nova Scotia, and the Great Lakes. Its arrival has taken a significant toll on native fish populations, particularly the cutthroat trout, which the U.S. National Park Service describes as having suffered a “decimating” decline due to lake trout predation and competition.
Origins and Impact of Lake Trout in Yellowstone
The first confirmed discovery of lake trout in Yellowstone Lake occurred in 1994. However, research indicates that these fish had been reproducing in the lake for several years prior. Montana State University researcher Andrew Munro noted in Yellowstone Science that based on the age and size of the trout found in 1994, reproduction likely began around 1989. Yet, the precise timing and method of their introduction remain uncertain.
The leading hypothesis, supported by the U.S. Geological Survey, suggests that lake trout were illegally transplanted into Yellowstone Lake from a nearby water body during the 1980s. Despite extensive study, experts have not been able to pinpoint the exact date or circumstances of this introduction.
Over the ensuing decades, efforts to manage the invasive population have been substantial, with approximately five million lake trout removed from Yellowstone Lake. Nevertheless, their presence continues to threaten native species and the overall health of the lake’s ecosystem, highlighting the ongoing challenges posed by invasive species within protected natural environments.