Researchers Find Broad Impacts from Lake Trout Invasion in Yellowstone

UW researcher Lusha Tronstad holds a large cutthroat trout captured in Clear Creek, a tributary stream of Yellowstone Lake, when she was a Ph.D. student in spring 2005. The numbers of spawning cutthroats in the lake’s tributaries have increased in recent years as a result of efforts to reduce the numbers of lake trout, whose presence has affected a number of other species in the Yellowstone Lake ecosystem since they were illegally introduced in the 1980s. (Lusha Alzner Photo)

Introduction of non-native lake trout in Yellowstone Lake has affected organisms from the microscopic level in the lake to large animals in the region, according to newly published research.

Zooplankton, cutthroat trout, river otters, osprey, bald eagles, bears and, likely, elk are among the creatures whose numbers, diet and behavior have been altered as a result of the presence of the invasive fish, says an article that appears today (March 20) in the scientific journal Science Advances.

The authors include Lusha Tronstad, research scientist with the Wyoming Natural Diversity Database at the University of Wyoming; National Park Service scientists Todd Koel, Jeffrey Arnold, Kerry Gunther, Doug Smith and Patrick White; and John Syslo of the Montana Cooperative Fishery Research Unit at Montana State University.

The scientists analyzed data spanning more than four decades, from 1972-2017, and concluded that the impact of lake trout in Yellowstone Lake — in particular, the decline of native cutthroat trout — has cascaded across the lake, its tributaries and the surrounding ecosystem.