A new five-year study by University of British Columbia researchers will focus on the impact of road salt on salmon habitat and baby salmon and how the public can help reduce its potential impacts.
The study, announced in early November, noted that Pacific salmon are in decline and posed the question of whether too much salt in critical salmon streams could be a cause. Adult salmon live in salt water but grow up in fresh water and there’s evidence that even moderate salt levels at a young age cause mortality and stunted growth in these fish.
The study itself will focus on the region around Vancouver, British Columbia, also known as the Lower Mainland. There is currently relatively limited monitoring of salt levels in the area’s creeks and streams, although there are various monitoring programs elsewhere across Canada and in the U.S., researchers said.
Chum salmon only spend about 30 to 45 days in freshwater, while coho spend more than a year, so that could be one species that is hard hit, but not the other, according to the university’s announcement.
Canadian federal and provincial regulations set maximum salt levels in streams, but these levels are not routinely monitored. No one has yet looked at patterns of salt exposure, for instance whether a short spike of salt is harmful, or noting if certain types of salmon might be affected more, researchers said.
Road salt generally contains mostly sodium and chloride, which is the same chemical makeup as table salt, but it also can contain other chloride salts such as magnesium, calcium and potassium chloride.
Some road salt formulations also contain sodium acetate and similar chemicals, researchers said. For example, road salts that are pet safe often contain calcium acetate. Most of these alternative de-icers are as toxic or more toxic than regular road salt when they enter streams, they said.
There have been a number of studies on the effects of road salt on freshwater fish in the Great Lakes region and some work on the effects of road salt on Atlantic salmon in eastern Canada and the U.S., but little is known about native Pacific salmon on the West Coast, they said.
Gravel and other similar substitutes for road salt, such as ground lava rock, increases traction, but does not melt the ice. Still, they are definitely less toxic to fish. The goal is not to eliminate road salt, but to work with local authorities and the general public to use less of it, they said.
For example, when individuals put salt on their sidewalks or driveways, researchers recommend spreading it thinly and evenly, to work better and use less.
The university is partnering with Simon Fraser University, the British Columbia Institute of Technology and Fisheries and Oceans Canada on the study, along with 13 local stream keeper organizations, to monitor salt levels in streams.
Researchers said they have background evidence that salt levels in B.C. streams are rising, as well as salt “pulses” in winter, so data from this study will help establish these patterns.