Cooperative Fish and Wildlife Research Units Program: Wyoming
Education, Research and Technical Assistance for Managing Our Natural Resources

Cutthroat trout populations are declining across the Western U.S. Hybridization with introduced rainbow trout, and backcrossing with parental species and other hybrids, has led to genetic introgression and the presence of hybrid individuals with a mix of ancestry. A recent study on the extent of cutthroat trout hybridization in the North Fork Shoshone watershed found no allopatric genetically unaltered streams. However in a subset of North Fork Shoshone tributaries pure cutthroat trout remain, raising the question of what mechanisms are allowing these cutthroat trout to persist. This project is a collaboration with Wyoming Game and Fish Department and U.S. Forest Service to identify and evaluate mechanisms that maintain cutthroat trout in the North Fork Shoshone River drainage despite potential for hybridization. If mechanisms are found, for example temporal segregation in spawn timing, management actions can be modified to promote cutthroat trout.