Modeling Hatchery Influence: Estimates of Gene Flow and pHOS for Washington State Coastal Steelhead Hatchery Programs


Published: August 2022

Pages: 72

Author(s): Gary Marston and Anja Huff


There are currently fifteen harvest-oriented steelhead hatchery programs operated by the Washington Department of Fish and Wildlife along Washington’s Pacific coast. Since 2010 these hatchery programs provide an average 15,000 steelhead for tribal and recreation harvest annually. However, hatchery steelhead also present ecological and genetic risks to wild steelhead populations. In 2008, WDFW adopted the Statewide Steelhead Management Plan (SSMP) to guide future management actions for both wild and hatchery steelhead. This plan provides a management framework, to balance the risks and benefits of hatchery steelhead by setting thresholds for allowable levels geneflow and the proportion of hatchery fish on the spawning grounds (pHOS). The plan also mandates the designation of Wild Steelhead Management Zones to protect select wild steelhead populations from future hatchery actions. The primary aim of this study was to assess the compliance of current WDFW operated hatchery steelhead programs along the Pacific coast with the standards set out in the SSMP and provide recommendations on measures achieve compliance with the SSMP. This was achieved by utilizing the Demographic Geneflow Model for segregated programs and the All-H-Analyzer for integrated programs. Where programs failed to meet the standards for geneflow and pHOS in the SSMP the models were used to scale release levels to meet the SSMP thresholds. A secondary aim was to identify WSMZ candidates along Washington’s Pacific Coast. Our criteria excluded any populations with ongoing on-station hatchery production and indicated selected indicated that there must be at least one WSMZ per water resource inventory area (WRIAs 19 to 24), with the selected populations having a 6-year average of >300 spawners. Our findings identified nine potential WSMZs that fit these criteria. Based on the findings, the coastwide change in production is recommended to decrease by 262,000 smolts, although if program specific recommendations are implemented the decrease may not be as extreme.