The importance of thermal refuges for Salmon

Salmon are sensitive to everything in the environment, even relatively small differences in the  the temperature of the water.

“Anything above 23 celsius, they have a hard time doing their biological function,” said Carol-Anne Gillis, a cost-shared biologist, working with the GMRC, the Listuguj Fisheries, and the Restigouche River Watershed Management Council (RRWMC).

She is working on the Strategic Management of Thermal Refuges in the Restigouche River Watershed project. They are looking at preserving – and enhancing – areas of cold water in the river that the salmon tend to hang around. These are important areas, at several different stages in their life cycle of the salmon.

If you ever travelled down the Restigouche River, and stepped out of your canoe into surprisingly cold water – you’re not crazy. There can be as much as a 10 degree difference in some places. There are now 1,825 classified “thermal refuges” identified.

There are “seeps,” where groundwater seeps into the river, and there are “confluence plumes”  where streams meet the main river, and start to spread out. Often, the cold water from a stream will meet the river, and be pushed to the side.

“So you might have this cold water space, but it’s only like a foot wide, and it’s on the shoreline,” said Gillis.

Part of Gillis’ work is to find ways to enhance these confluence plumes.

“What we can also do is create these instream structures where you can kind of, either give more energy to the small stream, so it can have a bigger space for fish in the main stem,” she said. “It’s kind of alike a cone. So instead of having a streamline of cold water on the shore line, hugging the shore line, well you can divert it, and create a bigger cone of cold water. So there’s more volume for fish.”

The seeps are a little more complicated to protect. They are protected the same way many other aspects of the river’s health is maintained – managing nearby land use.