Yellowstone Cutthroat (IMAGE) University of Wyoming Caption University of Wyoming 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 has 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. Credit Lusha Alzner Photo Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.