Yellowstone Cutthroat Trout (YCT) in Yellowstone Lake have been threatened for decades by the large invasive lake trout population.  Years of effort to reduce the lake trout now provide an opportunity for the non-hybridized, genetically pure YCT to rebound.  However, YCT populations have not been studied in more than 40 years and their status is uncertain. Montana State University Cooperative Fishery Research Unit will determine the status of population levels, determine which tributaries are currently being used for spawning, and overall genetic diversity and structure. This research will help guide future conservation and management of YCT.