Climate change risks for migrating salmon are shaped by warming and drought in coastal rivers
Across western North America, climate change and human land use are shifting patterns of river runoff and driving increased water temperatures in many watersheds.
These changes have contributed to major ongoing challenges for culturally and ecologically important aquatic species like Pacific salmon. In major salmon-bearing rivers like the Fraser, Columbia, and Klamath, increased warming and summer drought have taken a toll.
Read this open access paper on the FACETS website.
Sockeye salmon, which migrate during summer, are among the most vulnerable, and in the Fraser up to 90% of fish from some populations have died prior to spawning in warmer years. These impacts are relatively well understood, but the effects of climate on migrating salmon in thousands of smaller coastal watersheds are virtually unknown, limiting our ability to understand and manage the impacts of climate change on salmon fisheries.
Salmon are important to coastal First Nations people, whose food security and livelihoods are inextricably linked to wild salmon.
To address these uncertainties, we worked with the Haíɫzaqv (Heiltsuk) Nation to build a weir in the lower Koeye River — an undeveloped coastal watershed on the central coast of British Columbia — to monitor and tag migrating adult sockeye salmon shortly after they entered freshwater.
We tagged sockeye at the weir with passive integrated transponder tags and tracked their movement and survival from river entry to their spawning grounds above Koeye Lake using a network of in-river antennas.
We related survival and movement of migrating sockeye to the river conditions they encountered and found that warm water temperatures reduced survival and that drought conditions can exacerbate the negative effects of temperature and cause migratory delays.
All told, climate warming may have serious negative consequences for sockeye salmon in coastal watersheds despite their relatively short migrations, and climate-smart fisheries for sockeye will be essential for long-term fishery sustainability and population persistence.
Read the paper — Thermal sensitivity and flow-mediated migratory delays drive climate risk for coastal sockeye salmon by William I. Atlas, Karl M. Seitz, Jeremy W.N. Jorgenson, Ben Millard-Martin, William G. Housty, Daniel Ramos-Espinoza, Nicholas J. Burnett, Mike Reid, and Jonathan W. Moore
