Migratory Patterns and Genetic Population Structure of Coastal Cutthroat Trout in South Puget Sound

While anadromous cutthroat trout appear to be present in marine waters of south Puget Sound year-round, little is known regarding their movement in the freshwater and marine environment.  The current study was designed to describe (1) the genetic population structure of coastal cutthroat trout in three South Puget Sound streams and (2) the migration patterns during the marine phase of their lifecycle.   Tissue samples were collected from juvenile cutthroat trout indigenous to Skookum, Kennedy, and McLane Creeks to serve as baseline collections.  Additional tissue samples were collected from adult cutthroat in each of the inlets associated with the three creeks.  The genetic source population of these fish was unknown.  To describe the genetic population structure of the juvenile cutthroat trout collected in freshwater (genetic baseline) we genotyped samples at 66 single nucleotide polymorphism (SNP) loci and conducted pairwise tests for genetic differentiation.  Genetic assignment of fish captured in inlets to their population of origin was performed, and marine migration patterns were inferred from the genetic assignments.  This information in conjunction with ongoing spawning ground surveys conducted in study streams may allow fisheries managers to account for small-scale changes in abundance of Puget Sound and respond to conservation concerns more effectively.