Genetic influence from hatchery stocks on upper Willamette River steelhead Oncorhynchus mykiss, Information Report 2018-03

Identification Information

Citation

Originator: Oregon Department of Fish and Wildlife

Publish Date: June 2018

Online Link: https://odfw.forestry.oregonstate.edu/willamettesalmonidrme/home

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Marc Johnson

Job Position: REDD Program Genetics Analyst

Telephone: (541) 757-4263

E-Mail Address: Marc.Johnson@oregonstate.edu

Description

Abstract: In this study we used microsatellite markers to genetically characterize 1,012 unmarked (presumed to be naturally produced), juvenile Oncorhynchus mykiss, collected at Willamette Falls in 2009, 2010 and 2011, and from multiple locations throughout the upper Willamette River basin in 2014. From the genetic data, we estimated the proportion of each year’s sample that could be assigned as native resident rainbow trout, native winter steelhead, hatchery summer steelhead, the likely descendants of a discontinued hatchery winter steelhead program, or hybrids of these groups. We also attempted to assign individuals to pure or hybrid classes (e.g. F1, F2, backcrosses) and evaluated the predicted accuracy of these class assignments. Although the majority of fish analyzed in each year were assigned as native winter steelhead, we found evidence of natural production by introduced stocks of steelhead. Genetic influence from a discontinued winter steelhead hatchery program was most evident in the Tualatin, Yamhill, Molalla, and below-dam reaches of the North and South Santiam rivers. Pure and hybrid signals from introduced summer steelhead were almost entirely restricted to below-dam reaches of major eastern tributaries and the Molalla River. Evidence of non-native steelhead was nearly absent from above-dam reaches of major tributaries and the Calapooia River. Despite continued hatchery releases of summer steelhead in the Willamette River, we found no compelling evidence for the presence of first-generation hybrid offspring (F1s) that might result from hatchery summer and native winter steelhead matings. However, simulation analyses revealed low statistical power to confidently identify such individuals from our data. We recommend that areas containing native steelhead populations with high genetic integrity receive protection through directed conservation efforts, and continued genetic monitoring should be conducted to inform these efforts and future status reviews.

Purpose:

Time Period of Content: 2009-2014

Geographic Extent: Willamette River basin, Oregon

Status: Final

Use Constraints:

Format: PDF File

Data Quality Information

Lineage-Source: See methodology in report.

Data Information

No data information was supplied.

Entity and Attribute Information

Attributes Description: Genetic data; summarized in report. Raw data available upon request to the authors.

Is a physical copy maintained for reference at Headquarters? No