Cool Pools to Save Salmon Schools

KATIE O’NEILL© ALANNA DUMONCEAUX

Researcher Finds Cool Pools to Save Salmon Schools Kate O’Neill’s Passion Drives her to Help Keep Salmon out of Hot Water

From June 25 to July 1, 2021, British Columbia baked under temperatures reaching 49.6°C.

The unprecedented heat dome resulted in B.C. streams getting warmer, detrimental to cold-blooded salmon.

However, one researcher found a silver lining. The extreme heat created a greater differential between ambient stream temperatures and the cooler pools within them, fed by upwelling groundwater.

Researcher Kate O’Neill launched her project with two goals: first, to identify where groundwater enters streams, and second, to create a methodology for stream keepers to find cool pools so people could replicate her work.

“During 2019 and 2020, the summers were not extraordinarily warm, so it was difficult to identify thermal refugia (cool pools) within streams,” says O’Neill, whose 2019 research was funded by the Pacific Salmon Foundation (PSF) and the Pacific Institute for

Climate Solutions. Her master’s study in Ecological Restoration from Simon Fraser University and BCIT focussed on Vancouver Island’s Tsolum River.

The heat of 2021 made these cool refuge areas more obvious—and necessary for salmon.

Allan Chamberlain, Tsolum River Restoration Society (TRSS) director and volunteer, contributed to O’Neill’s research when he noticed thermal refugia while snorkelling the river

during the heat dome. The society mobilized research assistants to walk the lower Tsolum and document the cool spots, which they shared with O’Neill.

“By identifying these thermal refugia, we can help protect specific areas by increasing public awareness, and really focus our efforts on climate mitigation,” says O’Neill.

“This is important because as cold-blooded species, salmon are very sensitive to climate change and habitat threats,” says O’Neill.

“And salmon are vitally important to our ecosystem and extremely important culturally.”

Despite the positive identification of cool pools, the number of salmon using them appeared to decline over the hot summer period, which may suggest fish are more prone to predation when clustered in high numbers.

Locating areas of cool refuge— which can be as small as one metre by one metre—proves challenging. The work often relies on information provided by local swimmers, fisheries professionals, or people walking or snorkelling in streams.

In collaboration with TRRS volunteers, O’Neill verified thermal refugia by installing a series of data loggers to confirm whether the stream is fed by groundwater. Shielded from solar warming, they provide a cool-temperature refuge for salmon within a warmer river.

The data loggers—used in O’Neill’s research funded by PSF’s Community Salmon Program—are primarily financed by the Salmon Conservation Stamp,

purchased by anglers with their annual fishing license.

O’Neill has continued her research after completing her master’s while working for Current Environmental Ltd. Recently, in partnership with the TRRS and supported by PSF and Habitat Conservation Trust Foundation funding, they deployed a drone from BCIT’s Remotely Piloted Aircraft System Hub.

Using drones with infrared technology, they hope to identify anomalies in river temperatures, allowing larger areas to be studied more efficiently and effectively. Her ultimate goal is to support the identification and mapping of thermal refugia within all salmon-bearing streams in B.C.

“We still don’t know where a lot of these areas are, and we continue to rely on anecdotal information and citizen science from people who care,” says O’Neill.

Learn more about Pacific salmon at: psf.ca.

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