New study suggests winter road salt may be harming salmon eggs.
A study conducted by the Road Salt and Pacific Salmon Success Project has raised concerns about the impact of road salt runoff on coho salmon eggs in streams across Vancouver’s Lower Mainland (VLM). Preliminary findings suggest that high levels of salt in freshwater streams during winter could significantly harm salmon embryos, leading to high mortality rates and developmental deformities.
Salt Contamination in Freshwater Streams
The research, led by a collaboration between the University of British Columbia (UBC), Simon Fraser University (SFU), British Columbia Institute of Technology (BCIT), Fisheries and Oceans Canada, and community scientists, has monitored salt levels in over 30 streams in the VLM for three years.
The team found that road salt application during winter created sharp spikes in salt levels, measured as conductivity. These pulses exceeded British Columbia’s acute water quality guidelines for freshwater chloride more than 30% of the time, with some peaks reaching concentrations equivalent to 30% of seawater.
Impact on Salmon Eggs
Lab experiments simulated the effects of these salt pulses on fertilized coho salmon eggs. The results indicated that salt exposure shortly after fertilization significantly reduced survival rates. At chloride concentrations twice the recommended levels, survival decreased, while exposure to levels eight times higher resulted in more than 70% mortality. Surviving embryos often exhibited deformities, which would likely be fatal in natural environments.
Carley Winter, a zoology researcher involved in the study, noted that “salting roads at current levels in November or December, when many salmon species are spawning, could be dangerous to coho and chum salmon.”
Proposed Solutions
To mitigate the impact of road salt on salmon populations, researchers suggest adopting more efficient salting practices:
- For individuals: Applying only the necessary amount of salt to melt ice—approximately two tablespoons per square meter—and spreading it evenly rather than in clumps.
- For municipalities: Switching to brine solutions, which use up to 50% less salt and adhere better to roads, potentially reducing runoff into freshwater streams.
Future Research
The next phase of the project will investigate the non-lethal effects of salt exposure on salmon eggs and fry, such as growth and genetic impacts. Field studies will also examine the real-world impact of salt levels on coho hatching success during the next spawning season.
The findings underscore the potential environmental costs of winter road maintenance practices and highlight the need for sustainable alternatives to protect Pacific salmon populations.
