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

Wyoming Project

Yellowstone cutthroat trout hybridization in the North Fork Shoshone River

July 2016 - June 2018


Participating Agencies

  • Wyoming Game and Fish Department
  • Wyoming INBRE
  • U.S. Forest Service

The Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri has experienced substantial declines in abundance and distribution. Yellowstone cutthroat trout occupies 42% of its historic range, but only 28% of populations are genetically unaltered. Hybridization with rainbow trout Oncorhynchus mykiss may present the greatest threat to conservation of YSC. Introgression from RBT may lead to the breakdown of important local adaptations in native cutthroat trout subspecies, and lead to loss of fitness of these subspecies in their native habitats, the formation of hybrid swarms, and genetic extinction of pure cutthroat trout. This project is in collaboration with Wyoming Game and Fish Department and U.S. Forest Service. The goal is to determine the extent of hybridization within the North Fork Shoshone River drainage and evaluate the relationship between hybridization and environmental variables (e.g., temperature, discharge, slope). This will allow managers to identify priority tributaries and determine conservation potential of Yellowstone cutthroat trout in the North Fork Shoshone River drainage.