A recent study conducted by the Pacific Salmon Foundation, in collaboration with three northern Vancouver Island First Nations, reveals that water samples collected near active open-net salmon farms in British Columbia contain four times more pathogens harmful to wild salmon compared to samples from areas near inactive farms. Published in the peer-reviewed journal Scientific Reports, the research utilized environmental DNA analysis to detect bacteria, fungi, and viruses known to adversely affect wild salmon populations.
Dr. Emiliano Di Cicco, a researcher with the Pacific Salmon Foundation, emphasized the significance of these findings: “That gives us the confirmation that salmon farms can actually contain and amplify pathogens that can… therefore affect wild salmon that live in the area.” He recommends transitioning to closed containment systems to mitigate these risks.
The study supports the federal government’s decision to phase out open-net salmon farms in BC by 2029, a move aimed at protecting declining wild salmon populations. However, this decision came in the wake of Ottawa backing out of its promise to phase out open-net salmon farms in BC by 2025.
Mass Die-Offs and Disease Outbreaks Raise Alarms
Beyond pathogen amplification, open-net salmon farms have been linked to significant mass die-offs of farmed salmon. In 2024, a mass mortality event in Nootka Sound resulted in the loss of up to 1,000 tonnes of farmed salmon at a single facility. In just ten days, the farm lost 23 percent of 4,100-tonne licensed capacity. Similar mortality events were reported at other farms in Clayoquot Sound, Port Hardy, and Esperanza, with cumulative mortalities ranging from 4% to 26% between mid-May and early June.
These die-offs are sometimes attributed to disease outbreaks exacerbated by the high-density conditions of open-net pens. Piscine orthoreovirus (PRV), a virus found in over 70% of farmed salmon, has been identified as a significant concern. PRV can cause Heart and Skeletal Muscle Inflammation (HSMI), leading to lesions on the heart and muscular system, with mortality rates between 20% and 100%. The virus can spread from farmed to wild salmon, potentially impacting their ability to complete spawning migrations.
Environmental Impacts Extend Beyond Pathogens
Open-net salmon farms contribute to various environmental issues beyond disease transmission. Waste products, excess feed, and chemicals from these farms are discharged directly into surrounding waters, degrading local ecosystems. The accumulation of waste beneath farms can lead to oxygen-depleted zones, which in turn affect benthic organisms and overall water quality.
One of the most well-documented threats associated with open-net salmon farms is parasitic salmon lice, which pose serious risks to both farmed and wild salmon populations. These naturally occurring parasites thrive in the densely packed conditions of salmon farms, where thousands of fish confined in close quarters create an ideal environment for breeding.
Once populations explode within the farms, sea lice can spread to juvenile wild salmon migrating past these sites, often with fatal consequences. These parasites feed on the mucus, skin, and blood of salmon, causing open wounds that are prone to infection. A 2019 study found that up to 95% of wild juvenile pink and chum salmon died from sea lice infections in areas with intensive fish farming
Differing Perspectives on the Future of Salmon Farming
The federal government’s plan to ban open-net salmon farms in BC by 2029 has elicited mixed reactions. While environmental groups and some Indigenous communities support the transition to closed containment systems, industry representatives express concerns about the economic implications and feasibility of such a shift. The government has pledged to support affected communities and workers during the transition period.
Hereditary Chief Ernest Alfred of the Namgis First Nation strongly disputes industry claims downplaying the impact of salmon farms. He points to a noticeable rebound in wild salmon populations since the closure of most open-net farms in the Broughton Archipelago two years ago. Alfred emphasizes that the resurgence aligns with what First Nations leaders and environmental advocates had long predicted.
“We’re witnessing dramatic returns of salmon across the region, and this recovery will resonate along the entire coast,” he told CBC News. “We always knew that removing these farms would give wild salmon a chance to thrive again.”
As the debate continues, the study’s findings underscore the need for comprehensive strategies to address the environmental and ecological challenges posed by open-net salmon farming in British Columbia.
