Salmon farms are experiencing a growing problem of mass mortality

Since 2012, mass die-offs of farmed salmon have become more frequent and increasing in number, with some locations wiping out millions of fish at a time. These mass mortality events are often caused by stress factors such as fluctuations in ocean temperatures and poor living conditions, highlighting the need to improve animal welfare practices on salmon farms.

Approximately 70% of the salmon sold worldwide is farmed. There is a high mortality rate of fish before they are ready for slaughter, and there are serious concerns about the environmental impact of salmon farming and the welfare of farmed fish.

Six countries produce 92% of the world's farmed salmon: Norway, Canada, the United Kingdom, Chile, Australia, and New Zealand. Gerald Singh Researchers from the University of Victoria in Canada analyzed mortality data from these countries.

The researchers found that high-fatality events increased over time, particularly in Norway, Canada, and the United Kingdom, from 2012 to 2022. A total of 865 million salmon died during this period.

“We are talking about very large numbers,” Singh says. “In the case of Norway, the worst ranged from about 935,000 fish lost in a month to just under 5 million. In Canada, the worst 10 per cent disaster ranged from about 935,000 fish lost in a month to just under 5 million. Between 10,000 and 3.8 million fish were lost.”

If this trend continues, researchers predict that future fatal crashes could cause up to 5.14 million deaths in Norway, 5.05 million people in Canada and just over 1 million people in the UK.

Environmental stressors such as marine heatwaves and lack of oxygen in the water, as well as sea lice infestations, can trigger these mass die-offs. To reduce the impact of these stressors on salmon, Singh says better animal welfare practices need to be implemented, such as not overcrowding fish pens.

“These events can have significant impacts on local economies, communities and ecosystems,” he says. “For example, if communities that rely on these industries are stripped of their farming permits, this can have a significant impact on local economies and livelihoods.”