New WDFW research finds link between coastal steelhead survival, changing ocean conditions
New Washington Department of Fish and Wildlife (WDFW) research sheds light on the link between a changing climate and ocean and ecosystem conditions; and winter steelhead survival on the Washington coast.
WDFW scientists examined wild winter steelhead in rivers on the western Olympic Peninsula and flowing into Grays Harbor, including the Chehalis, Hoh, Humptulips, Queets, Quillayute, and Quinault. WDFW used data collected since the early 1980s, including estimates of spawner abundance, harvest-related mortality, and individual fish ages, to assess whether recent declines in survival of multiple coastal steelhead populations were connected with changes in ocean ecosystem conditions.
Steelhead, which can exceed 30 pounds, are the state fish and a highly regarded game fish. They are the same species as rainbow trout, but while rainbow trout remain in fresh water, steelhead are “anadromous” and travel to the ocean before returning to spawn in fresh water. This study focuses on winter-run steelhead, which return to fresh water between November and April and spawn in late-winter and spring.
Research findings
“Our team’s findings provide evidence that increased temperatures and intensified competition at sea have contributed to negative trends in survival for many steelhead populations, outside of freshwater factors that may affect individual populations,” said Jan Ohlberger, a WDFW research scientist and the study’s lead author. “The study adds to our understanding of why coastal steelhead survival rates have declined over the last five decades and highlights the potential impacts of climate and ecosystem change on salmon and steelhead populations.”
The research found:
- Immature and adult steelhead survival rates have declined over time, and survival trends across populations were strongly associated with changing ocean conditions.
- Summer sea surface temperatures and pink salmon abundance in the north Pacific Ocean were negatively associated with coastal steelhead survival. Pink salmon and steelhead may compete for prey or otherwise be linked in the marine food web.
- The North Pacific Gyre Oscillation, a broad-scale index that measures sea surface height variability, which correlates with fluctuations of salinity and nutrients, was positively associated with steelhead survival.
If not for these variables, the research showed, coastal winter steelhead survival and abundance would have been nearly constant over the last four or five decades.
“Wild steelhead abundance has decreased across much of this species’ range over the past 40–50 years,” Ohlberger said. “Declines in abundance and life history diversity have led to several steelhead populations in Washington being listed under the federal Endangered Species Act (ESA). Understanding whether environmental changes are shaping these trends is critical for well-informed conservation and management decisions.”
Unlike in most other parts of the state, coastal steelhead are not currently listed under the ESA. A petition to list Olympic Peninsula steelhead was submitted to the National Oceanic and Atmospheric Administration (NOAA Fisheries) in 2022. NOAA Fisheries has not yet issued an official determination regarding the ESA petition.
Unlike salmon, steelhead can spawn more than once. Because they spend a significant portion of their juvenile and adult life stages in fresh water, they are particularly susceptible to habitat degradation and other pressures during freshwater residence.
Refer to the study, available from the journal Fish and Fisheries and WDFW’s website.
To complete the study, WDFW collaborated with and incorporated data from the Hoh Tribe, Quileute Tribe, and Quinault Indian Nation.
“An indicator of ecosystem health, steelhead are important to recreational anglers, tribes, and local communities and economies,” Ohlberger said. “WDFW is committed to conserving coastal steelhead while offering meaningful fishing opportunities.”
WDFW continues to operate under its Statewide Steelhead Management Plan, which requires the Department to prioritize the sustainability of wild coastal steelhead runs by focusing on healthy levels of abundance, productivity, diversity, and distribution.
For more information about coastal steelhead management, visit WDFW’s webpage.
