Title: Declining patterns of Pacific Northwest steelhead trout spawner abundance and marine survival

Authors: Neala Kendall, Gary Marston, and Matt Klungle (Washington Department of Fish and Wildlife)

Presented by: Erik Neatherlin (Washington Department of Fish and Wildlife)

Abstract: Evaluating trends in steelhead population abundance and productivity, whether and how these trends differ among neighboring regions, and the spatial co-variation of these trends is essential for successful management. Steelhead population abundance trends have fallen dramatically in Puget Sound and the Georgia Basin and have also decreased in other coastal parts of Washington State and British Columbia. To better understand the patterns and put them into context, we gathered data on wild steelhead abundance trends since 1980 and compared their declines among regions. Next, we assessed marine survival trends (smolt-to-adult return rates) from 48 wild populations or hatchery stocks from multiple regions of the Pacific Northwest since the late 1970s. We found that Puget Sound and Georgia Basin spawner abundance values have decreased the most of all regions, though declines were the common pattern seen throughout. Puget Sound steelhead SAR trends were also significantly different from those from other areas, specifically the Washington and Oregon coast, lower Columbia River, and the Strait of Juan de Fuca. Though coastal, lower Columbia, and Puget Sound (grouped with the Keogh River SAR time series) SARs all declined in the early 1990s, a rebound was seen for coastal and lower Columbia populations in the late 1990s whereas Puget Sound values have remained low. We compared the spatial covariation in SAR time series among steelhead populations and compare these results to what has been observed for other salmon species and how these potentially relate to marine environmental drives. We also evaluate different trends in the SAR time series by region and how these are also associated with changing environmental conditions.

Neala Kendall, PhD

Research Scientist

Statewide Quantitative Synthesis and Reporting Unit

Science Division, Fish Program

Washington Department of Fish & Wildlife

206-371-7161