Genetic Considerations for Sourcing Steelhead Reintroductions: Investigating Possibilities for the San Joaquin River

Steelhead trout (Oncorhynchus mykiss) historically occurred in all major watersheds along the west coast of the United States. They can be a vital part of a healthy riverine ecosystem, are highly valued for fishing, and have been greatly affected by human activities. Given these traits, and that the San Joaquin River in the Central Valley of California is under consideration for steelhead reintroduction, emphasis has recently been placed on conservation efforts to reintroduce steelhead into streams in which they were once native. There are many issues to consider when deciding how, where, and in what manner to reintroduce steelhead, including genetic considerations. One primary factor is determining the source population for reintroduction. In this paper, we consider the many important genetic aspects to consider when determining the source for steelhead reintroduction, and outline the genetic data needs when determining sources for reintroduction. We discuss the lessons learned from previous reintroductions in relation to a reintroduction scenario in the San Joaquin River, and recommend potential source populations.