A recent peer-reviewed study published in the Journal of Fish Diseases adds to the growing body of evidence challenging the assumption that removing salmon farms leads to lower sea lice levels on wild Pacific salmon.

The study examined eight years (2017–2024) of sea lice data from juvenile chum and pink salmon in British Columbia’s Discovery Islands, a region where salmon farms have been inactive since 2022 following a phased removal starting in 2021.

Contrary to expectations, 2024 recorded some of the highest sea lice levels observed over the study period—despite the absence of active farms. Similar trends were noted in the Broughton Archipelago and other areas regardless of farming activity.

“These findings demonstrate that the evidence does not support the narrative of ‘no farms equals no sea lice,’” said Lance Stewardson, RPBio., CPESC, Director at Mainstream Biological Consulting Inc. and co-author of the paper. “Long-term monitoring shows that significant natural sources of sea lice exist in the marine environment.”

Data was collected in partnership with local First Nation stewardship teams, reinforcing the value of collaborative, science-based monitoring. While sea lice levels have generally remained low over the years, natural fluctuations were evident—highlighting the complexity of marine ecosystems.

The study’s conclusions align with previous findings, including the Canadian Science Advisory Secretariat’s 2022 report, which found no statistical correlation between lice levels on wild and farm-raised salmon. A 2023 literature review of Atlantic salmon also identified overestimations of farm-related impacts.

For stakeholders, these findings underscore the need for nuanced, evidence-based policies and continued ecosystem monitoring—not assumptions—when managing wild salmon health and aquaculture practices.