Eight-year study finds no clear link with B.C. salmon farms and sea lice

No consistent sea lice drop on wild salmon after B.C. open net-pen farm closures, study finds

An eight-year study found no consistent decline in sea lice on wild juvenile Pacific salmon after open net-pen salmon farms were removed from British Columbia’s Discovery Islands, challenging claims that farm closures directly reduce sea lice levels. Published in the Journal of Fish Diseases, the research analyzed wild chum and pink salmon data from 2017 to 2024 in the region defined by Fisheries and Oceans Canada.

“Sea lice levels on wild salmon in 2024 were among the highest recorded during the last eight-year period in the Discovery Islands, despite the closure of salmon farms,” said Lance Stewardson, RPBio., CPESC, Director of Mainstream Biological Consulting Inc., and one of the paper’s authors. “A similar pattern with a low sea lice infestation in 2023 and higher levels of sea lice infestation in 2024 was also observed in the Broughton Archipelago and other areas with and without salmon farms. These findings demonstrate that the evidence does not support the narrative of no salmon farms, means no sea lice.”

The removal of salmon farms in the Discovery Islands began in 2021, with no active farms remaining since 2022. However, data collected with the involvement of local First Nation stewardship staff shows that 2024 recorded some of the highest sea lice levels observed on wild juvenile salmon during the eight-year study period. Overall, the monitoring data from 2017 to 2024 indicate that sea lice levels have generally remained low, with natural year-to-year fluctuations.

Aquaculture sector reacts to Canadian government’s ‘devastating decision’ to close Discovery Islands salmon farms

“This long-term monitoring shows that significant natural sources of sea lice exist,” said Stewardson. “Our findings disprove the claim that salmon farms are the sole driver of sea lice on wild Pacific salmon in the near-shore environment and underscore the need for continued monitoring.”

The study’s findings are consistent with 2024 data from the Broughton Archipelago and build on a broader body of research suggesting that the impact of salmon farms on sea lice levels in wild salmon populations may be overstated.

A literature review published last year similarly found that the effects of sea lice from farms on wild Atlantic salmon had often been overestimated. In 2022, the Canadian Science Advisory Secretariat (CSAS) also concluded there was no statistical correlation between sea lice levels on wild and farmed salmon.

In April 2022, a Federal Court ruling also reaffirmed conclusions from nine peer-reviewed reports that salmon aquaculture in British Columbia (B.C.) poses “no more than a minimal risk of harm to the Fraser River Sockeye salmon.”

On December 17, 2020, the Minister of Fisheries, Oceans, and the Canadian Coast Guard announced in a news release that salmon farming in the Discovery Islands would be “phased out” within an 18-month period. Specifically, no further licenses would be issued and the introduction of new fish of “any size” to those fish farms during this period would be prohibited. It mandated that all fish farms would “be free of fish” by June 30, 2022, but that the existing fish at these sites could complete their growth cycles and be harvested.

Read the full study.

Related Posts

Responsibility

Behind one First Nation’s fight to keep its salmon farms afloat

The Kitasoo Xai’Xais Nation fights regulation and celebrity backlash as salmon farming’s future in British Columbia hangs in the balance. 

Responsibility

First Nations coalition unveils plan for salmon farming in British Columbia waters

The Coalition of First Nations for Finfish Stewardship releases a “responsible, realistic and achievable” plan for an Indigenous-led blue economy. 

Responsibility

Some First Nations are asserting their right to farm salmon, despite pending government closures

With salmon farm closures imminent, some First Nations are taking action to preserve ocean-based farming and assert Indigenous sovereignty. 

Intelligence

Report: Moving BC salmon farms to land may not be economically viable

Regulatory uncertainty, high capital cost, low ROI and few incentives were identified as hurdles to moving BC salmon farms onto land.