Activists claim the removal of BC salmon farms changed sea lice levels. Not true, say researchers

Scientists and salmon farmer Mowi Canada West have roundly rejected the claim of anti-fish-farm activists that the removal of salmon farms in the Broughton Archipelago and Discovery Islands in British Columbia has made those areas sea-lice free.

Since 2018, 13 salmon farms have been removed from the Broughton Archipelago region, while in the Discovery Islands, all 11 salmon farms are now gone.

On October 4, non-profit group Wild First published a youtube video in which they claimed the closures of fish farms operated by Mowi and Cermaq Canada have “immediately” resulted to wild salmon being free of sea lice. Campaigner Alexandra Morton made similar claims in her “no farms, no lice” video in April.

But third-party researchers whom the salmon industry has contracted for many years to conduct annual sea lice counts on wild juvenile salmon have rejected that claim.

“The long-term data suggests that regardless of farm status, sea lice infestation rates on wild juvenile salmon fluctuate annually,” said Lance Stewardson of Mainstream Biological Consulting, who has been doing sea lice monitoring on wild salmon since 2004.

For instance, data shows that the spring of 2022 showed the highest sea lice infestation in the Boughton Archipelago since 2016. In the Discovery Islands area, the infestation on wild salmon in years 2021 and 2022 – when salmon farms were already gone – was within the level seen between 2017 and 2020 when farms were operational, noted Stewardson.

Jennifer Russell, a biologist at Pacificus Biological Services, sais a long-term study is the most effective way to achieve reliable results.

“Collecting data from before, during, and after operations is the best way to achieve answers. Examining a particular issue in this way is more reliable than opportunistic data collection,” she said.

In August, activists also attributed the  strong returns of wild salmon to BC waters to the shutdown of salmon farms. However, Fisheries and Oceans Canada said the strong numbers of returning wild salmon is due to the cooler weather.

Read also: Cooler conditions, not farm shutdowns behind healthy returns of wild salmon to BC rivers

Mowi Canada West said sea lice numbers continue to be monitored closely on salmon raised at BC farms, and the process includes veterinarian oversight.

“Mowi acknowledges that effective sea lice management is important for fish welfare and to
ensure sea lice on salmon farms do not negatively impact wild salmonids,” the company said. It publishes sea lice counts monthly on its website.

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