Salmonid Response to Rising Stream Temperatures in the Chehalis River Basin
Abstract
Stream temperatures in the Pacific Northwest are projected to increase with climate change, placing additional stress on native salmonid species. In the Chehalis River basin, Washington, USA, peak summer stream temperatures are predicted to increase by as much as 3°C by late-century. In this study we assessed the impact of increased stream temperatures on four salmonid species (spring-run Chinook salmon Oncorhynchus tshawytscha , fall-run Chinook salmon O. tshawytscha , coho salmon O. kisutch , steelhead O. mykiss ) in the Chehalis River basin. Using life cycle models, we estimated the potential consequences of increased stream temperature on these species using species- and life-stage-specific relationships between temperature and survival. Additionally, we assessed the potential for habitat restoration, including floodplain reconnection and increased stream shading from riparian planting and growth, to offset the effects of future temperature increases. We applied a temperature effect on rearing survival for all species, however the magnitude of the effect varied among species. Coho and steelhead rear in streams throughout the entire summer, and therefore experience the warmest summer temperatures, however steelhead are more tolerant of higher temperatures than coho. Juveniles of both runs of Chinook salmon migrate out of fresh water before summer temperatures reach their peak, therefore temperature had a diminished effect on rearing survival for these two species. Spring-run Chinook salmon are the only species with adults holding in the river during the warmer summer months, and therefore they are the only species for which peak temperatures affect prespawn survival, one of the most sensitive parameters in our life cycle model. Because of this, spring-run Chinook are particularly vulnerable to stream temperature increases. Results from the life cycle models indicated that increased summer temperatures produce significant declines in spawner abundance for coho and spring-run Chinook salmon, and small decreases for fall-run Chinook salmon and steelhead. When the life cycle model included proposed habitat restoration actions there were opportunities to mitigate the negative impacts of future increases in temperature.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP41C2331F
- Keywords:
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- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0481 Restoration;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY