Road salt could be deadly for salmon

Salt concentrations in British Columbia streams are decreasing the survival rate of salmon eggs, according to preliminary results from the Road Salt and Pacific Salmon Success Project research group.

Lethal amounts for salmon

The results have not yet been peer-reviewed, but reveal that chloride levels may have exceeded the amounts recommended by the provincial and federal governments by 10 times in Vancouver-area waterways.

This is an extreme level, and this level occurs between November and March. This is the period when salmon, particularly coho and chum, return to Vancouver to reproduceexplains one of the researchers, Clare Kilgour, a student in the zoology department at the University of British Columbia (UBC).

Chloride can come from natural sources, but most of it that enters fresh waterways is associated with the application of sodium chloride, more commonly known as salt.

The salt released on the roads is carried away by melting snow, or rainwater, and ends up in manholes, then in waterways.

Over four winters, the researchers collected and analyzed data on around thirty rivers. They also exposed salmon eggs after they had been fertilized to chloride levels similar to their discovery.

The highest levels cause 100% of egg mortality.

These peaks in exposure occur even during mild winters, and only one day is enough for them to be fatal for embryos.

High salt levels were seen three times a week, in the worst weeks of wintersays Clare Kilgourelle.

The project Road Salt et Pacific Salmon Success is a collaboration between theUBCSimon Fraser University, British Columbia Institute of Technology, Fisheries and Oceans Canada and several volunteer groups.

These are the volunteers of the group Stoney Creek Environment Committee who raised the alarm about these high quantities of salt in rivers.

We found that in the part of the stream with higher salt concentrations, mortality [des embryons] is higher. And when fish are born, they have malformationsexplains John Templeton, president of Stoney Creek Environment Committee.

The volunteer has been involved in protecting the streams of Burnaby, near Vancouver, for more than 20 years. The latter are restored to allow the return of salmon to urban environments, because their population has declined considerably.

Burnaby has 90 small streams. Salmon probably spawn in fewer than 10 or 12 of these streams. So this is a big problemhe said.

Less salt on the roads

More than 5 million tonnes of road salt are used in Canada each year to ensure road safety, according to the federal government.

Researchers recommend using only the amount of salt needed to melt the ice. It only takes two tablespoons of salt to cover one square meterexplains Clare Kilgour.

Some municipalities, such as the City of Vancouver, already use mixtures containing 50% less salt, which would be more effective and more economical.

Other initiatives, such as de-icing roads with beet juice, require caution because high sugar levels could cause other environmental problems, the researcher said.

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The City of Vancouver recognizes that salt spraying on roads contaminates waterways and damages nearby vegetation, harms birds and wildlife, and infrastructure.

To limit this impact, municipal equipment is equipped with temperature sensors that help adjust the use of salt on the roads.

John Templeton points out that the research and work of volunteers has already borne fruit at Simon Fraser University, where salt storage and spreading practices have been modified to be safer for both the environment and the population. .

The idea is to collaborate, raise awareness and make them realize that they can have a positive impacthe says.