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Tracking Thermal Stress in Salmon Streams

Posted by Sue Mauger at May 10, 2017 08:45 PM |
The Canadian Journal of Fisheries and Aquatic Sciences published our paper this month about summer temperature regimes in southcentral Alaska streams and the potential implications for Pacific salmon. With five years of data from 48 streams across the Cook Inlet watershed, it is clear that salmon are already experiencing thermal stress and that over the next 50 years, chronic and sub-lethal effects will become more likely.
Tracking Thermal Stress in Salmon Streams

Daily mean stream temperatures from 2008 to 2012 at four sites during the open-water season.

Our paper: "Summer temperature regimes in southcentral Alaska streams: watershed drivers of variation and potential implications for Pacific salmon" has just come out in the Canadian Journal of Fisheries and Aquatic Sciences. We posed some specific questions: Which streams run hot? Which streams run cold? And does that change year to year? We also considered the potential implications for different salmon species and life stages now and in the future.

A collaborative network of federal, state, tribal and community entities collected data from 2008–2012. Sue Mauger, Cook Inletkeeper's Science Director, and co-authors Rebecca Shaftel and Daniel Rinella from the University of Alaska Anchorage, and Jason Leppi with The Wilderness Society found that some streams will remain as important cold-water habitats supporting healthy salmon populations for generations to come. But some streams are warming and will continue to do so putting cold-water loving salmon under increasing stress.

Water temperature in the Deshka River, which is a large lowland tributary to the Susitna River and a large producer of Chinook salmon, reached above 76 oF in 2009. This baseline dataset will allow us to accurately assess the rate of change in our watersheds in response to a changing climate. We continue to monitor 17 streams in Cook Inlet including the Deshka River where maximum temperatures reached 76.6 oF in 2016.

Our paper concludes that targeted management strategies can increase resilience in freshwater systems as our climate warms, such as improving riparian vegetation to shade streams, restoring fish passage to provide access to cold-water refugia, and identifying sensitive areas for conservation. These strategies plus continued monitoring to provide fisheries managers with current information is our best chance for long-term viability of the region’s salmon populations. Our research and protection efforts are now guided by this stream-specific information.

We are happy to see that new regional water temperature monitoring networks have started recently in Bristol Bay, Kodiak Archipelago and in southeast Alaska.

The article is open access and available here: http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2016-0076

You can read more about our stream temperature work here.