A 2026 monitoring report commissioned by Mowi Canada West found sea lice on 35.8 per cent of wild juvenile salmonids analysed in British Columbia’s Broughton Archipelago following several years of salmon farm closures.
Mainstream Biological Consulting prepared the report. Researchers used beach seines to sample fish at 17 sites chosen in relation to former Mowi aquaculture sites on April 16 and May 14 during the expected peak outmigration period.
The Center for Aquatic Health Sciences examined 508 fish, of which 182 carried lice. The survey documented infestation in this sample, but its two sampling events did not establish the effect of farm closures or the proportion of lice originating from farms.
The laboratory sample comprised 200 chum, 292 pink, 15 coho and one sockeye salmon. Prevalence was 37 per cent in chum and 33.2 per cent in pink salmon. Ten coho were infested, as was the sole sockeye, leaving those species represented by much smaller samples.
Field crews caught 5,689 salmonids, including 5,361 pink and 312 chum salmon. Of these, 292 pink and 200 chum were examined, alongside all coho and sockeye caught.
The analysts counted 340 lice, comprising 93 Lepeophtheirus salmonis and 247 Caligus clemensi. Abundance averaged 0.67 lice per fish examined, while infested fish carried an average of 1.9 lice.
Mowi’s earlier annual reports recorded aggregate prevalence of 32.5 per cent in 2022, 13.3 per cent in 2023, 42.2 per cent in 2024 and 21.8 per cent in 2025. The figures showed substantial variation rather than a consistent downward sequence.
The surveys changed over that period. Sampling covered 45 sites in 2022–23 and 17 sites in 2024–26, with three events in 2023 and two in the other years. The 2026 collection target also increased to 30 fish per target species where available, from 15 in 2024–25.
A peer-reviewed study published in Diseases of Aquatic Organisms in 2025 examined 2,868 chum and pink salmon collected at 14 Broughton sites during 2016–24. Its authors reported that farm production fell from 21,645 tonnes at 17 facilities in 2019 to 614 tonnes at two facilities in 2024.
In that dataset, prevalence peaked in 2022 at 53.7 per cent for chum and 62.9 per cent for pink salmon. Prevalence fell in 2023 before increasing in 2024 to levels similar to or above those recorded during 2016–21.
Salmon Coast Field Station, which runs a separate long-term programme, said its data repeatedly indicate an association between open net farms and disease and parasitic infections affecting nearby wild juvenile salmon.
The Broughton phase-out followed a 2018 accord involving three First Nations and the provincial government, covering 17 sites. The transition got underway in 2019; by the end of 2022, 10 farms were scheduled to have closed, while the remaining seven could continue only with First Nations agreements and federal licences.
The regional phase-out is separate from Canada’s coast-wide policy to prohibit open-net salmon aquaculture in British Columbia by June 30, 2029. Salmon farmers have challenged this federal transition policy.