Evaluating natural productivity and genetic interaction between a segregated hatchery stock and a wild population of steelhead trout (Oncorhynchus mykiss) in Eagle Creek, Oregon

Andrew Matala1*, William Ardren1, Doug Olson2, Maureen Kavanagh2, Bill Brignon2, and Jeff Hogle2

1U.S. Fish and Wildlife Service (USFWS), Abernathy Fish Technology Center,

Conservation Genetics Program, 360-425-6072;

1440 Abernathy Creek Rd., Longview, WA 98632

2U.S. Fish and Wildlife Service (USFWS), Columbia River Fisheries Program Office, Hatchery Assessment Team, Vancouver, WA 98683

Hatchery propagation of steelhead trout at Eagle Creek National Fish Hatchery (ECNFH) was implemented as mitigation for loss of fishery resources in the Columbia River basin. The original ECNFH winter-run broodstock was largely derived from out-of-basin Big Creek Hatchery stock from the Lower Columbia River with a component of local natural-origin (NOR) stocks. Hatchery-origin (HAT) steelhead return to Eagle Creek from December through March, whereas NOR late-run steelhead return to spawn in Eagle Creek from February to June. This temporal distinction has been viewed as advantageous because it allows for a targeted fishery on early returning HAT steelhead. Managers have assumed few matings occur between NOR and HAT fish because of distinct spawning locations and differences in spawning time. Redd counts indicate peak spawning for NOR steelhead occurs in May while the peak spawning of HAT fish at ECNFH occurs in February. The North Fork Eagle Creek is believed to be the major spawning area for NOR fish, while natural spawning of HAT fish is thought to occur primarily in the mainstem Eagle Creek. We conducted genetic structure analyses using 16 microsatellite loci to evaluate geneflow and relative productivity among naturally spawning HAT and NOR steelhead throughout the Eagle Creek watershed during return-years 2005 and 2006. Significant population heterogeneity (Fst = 0.018; CI 0.012-0.025) was observed between juveniles from the ECNFH raceways and NOR juvenile groups including North Fork Eagle Creek. We examine risks associated with observed levels of geneflow between NOR and HAT groups in the wild.

2008 Pacific Coast Steelhead Meeting Boise, ID

March 4-6, 2008