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Impacts of climate change on key aspects of freshwater salmon habitat in Washington State

Impacts of climate change on key aspects of freshwater salmon habitat in Washington State. Photo: Peter Essick. By Nathan Mantua, Ingrid Tohver and Alan Hamlet. Focus of our study. Key questions of how climate change will affect the following: 1. summertime water temperatures?

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Impacts of climate change on key aspects of freshwater salmon habitat in Washington State

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  1. Impacts of climate change on key aspects of freshwater salmon habitat in Washington State Photo: Peter Essick By Nathan Mantua, Ingrid Tohver and Alan Hamlet

  2. Focus of our study Key questions of how climate change will affect the following: 1. summertime water temperatures? 2. summer low flows and flood peaks? 3. hydrologic changes that alter the freshwater productive capacity for salmon?

  3. Approach to these key questions Global Climate Change Models Two emission scenarios: A1B (moderate) B1 (low) Regional shifts in temperature and precipitation for Washington State during three future timeframes: 2020s, 2040s, 2080s Projections of future water temperatures Projections of future extreme high and low flows Effects on freshwater salmon habitat

  4. Part 1: Salmon responses to increased summertime stream temperatures • Salmon are a cold water species • Water temperatures that are too warm have negative impacts on salmon: • Disease susceptibility • physiological stress • thermal barriers to migration • competitive disadvantage to warm water species • Differential impacts depending on populations

  5. Klamath River fish kill 2002 Extremely low flows and a very warm waters combined with high fish densities and rapid pathogen transmission resulted in massive mortality of adult chinook salmon in the lower Klamath River www.oregonwild.org

  6. Disappearing sockeye in 2004 • Lake Washington sockeye run • June/July water temperatures > 70oF • 200,000 sockeye disappeared after passing through the ship canal in June and July • Fraser River sockeye run • Peak temperatures of 71oF • 1.3 million sockeye unaccounted for • In both cases, unusually high water temperatures contributed to extreme pre-spawning mortality

  7. Upper Thermal limits for salmon

  8. Projected Loss of PNW Salmon Habitat over the Next Century NRDC report 2002 Based on the temperature increases from 8 different climate change scenarios, Washington state loses 5-20 % of viable salmon habitat by the 2090s.

  9. Weekly observed temperatures Water Temperature (oC) Water temperatures correlated to air temperatures Observed hourly temperatures Temperature (oC) Summer weeks 2001 Air Temperature (oC)

  10. Future air temperatures used to project weekly water temperatures Temperature (oC) Photo: Forrest Fishings Summer weeks

  11. Warming trends of air and water temperatures across Washington State

  12. Thermal stress season: Columbia River • Extending the season of thermal migration barriers for migrating salmon up to 12 weeks Extended periods weekly average water temperatures > 21C

  13. Thermal stress season:Lake Washington • Lake Washington’s Ship Canal is also projected to have chronically stressful summertime water temperatures for salmon • this overlaps with adult sockeye and summer chinook spawning migration times Number of weeks exceeding 21oC Week exceeding 21oC

  14. Water Temp summary • Increased thermal stress for many salmon populations in Washington state • Longer duration of thermal stress season distributed across greater number of streams • More extreme thermal stress in eastern Washington, but also problematic for some waters in western Washington

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