Phasing out open net-pen salmon farming in British Columbia

Abstract

Canada has committed to banning salmon open net-pen aquaculture in British Columbia by 2029 and is transitioning the industry to closed containment technologies for salmon farming.

Salmon aquaculture production around the world is based on a standard infrastructure consisting of cages moored in nearshore marine environments, farmed Atlantic salmon, and intensive feeding systems. This same infrastructure is implicated in environmental problems where salmon is farmed. Aquaculture nets are porous and, as such, allow for the exchange of pathogens—viruses, bacteria, and parasites—between farmed fish inside the cages and wild fish and shellfish outside the cages. In this issue of Science Advances, Krkošek et al. (1) provide critical new insights into the risks of pathogens from salmon aquaculture for wild salmon species in British Columbia (BC). Their research, coupled with similar work, has been critical in establishing an independent assessment of the environmental impact of BC’s farmed salmon industry on wild salmon (Fig. 1) and ocean ecologies. The efforts have also been foundational to a recently announced ban on open net-pen aquaculture and a transition to closed containment technologies for farming salmon in BC.

Fig. 1. Two pink sockeye salmon swimming in different directions.

CREDIT: Milton Love, Marine Science Institute, University of California, Santa Barbara, CA (https://usgs.gov/media/images/image-sockeye-salmon).

Wild salmon populations in BC have been in significant decline in recent years, unlike the North Pacific where salmon stocks are supported through hatchery production. The causes for the decline in wild salmon populations in BC are complex: They include overfishing by commercial companies, changing ocean conditions and ocean warming, the degradation of freshwater environments that are crucial to the reproduction of wild salmon, and salmon aquaculture. An additional challenge is that the declines vary by specific salmon species and by region within BC. While the causes are multiple and may work in tandem, in southern BC, where salmon aquaculture is active, wild salmon have fared worse. This situation has prompted long-term research on the causes with many studies linking the decline of wild salmon with “exposure to salmon farms or pathogens of farmed salmon” (1).

The three pathogens highlighted by Krkošek et al. are of particular interest because of their prevalence in farmed salmon cages and strong evidence that they are infecting wild salmon in BC. An in-depth and careful analysis of these pathogens reveals several important insights into the relationship between pathogens, aquaculture, and wild salmon. First, the effects of pathogens on wild salmon are far more serious than they are for farmed fish because they affect the fitness of wild salmon to survive in the marine environment. Second, salmon cages typically contain hundreds of thousands of fish and these environments are ideal for the propagation of pathogens, which increases the risks to wild fish. The problem with salmon aquaculture is similar to industrial livestock sectors where pathogens are amplified because they thrive when many animals are confined in dense numbers (2). Third, pathogens may originate from live farmed salmon in cages, but disease transmission can also occur through the discharge of biological waste into the marine environment from fish processing or net cleaning. This is a source of transmission of both piscine orthoreovirus and mouthrot to wild fish. Fourth, treating pathogens has become increasingly challenging. The use of chemical treatments for sea lice, for example, was initially very successful through the 2000s. However, the continued use of chemicals has made this parasite resistant to conventional approaches, a process that is familiar to farmers in terrestrial agricultural contexts where the resistance of pests to conventional chemicals is well documented. Mechanical approaches to sea lice have been introduced as an alternative, but they lead to considerable stress for farmed fish that compromises their growth and increases their vulnerability to pathogens. Concerns have also been raised about how mechanical methods of sea lice treatment end up returning this parasite to the marine environment and potentially affecting local wild salmon populations. Finally, Krkošek et al. raise questions about how warming sea ocean temperatures may only exacerbate the situation.

This study presents a much greater cause for concern compared to existing science advice provided by the Canadian Science Advisory Secretariat (CSAS) to Canada’s Department of Fisheries and Oceans (DFO). CSAS is the official body that is responsible for providing DFO with analysis and risk assessments of ocean ecosystems including wild salmon. CSAS reports and analyses have consistently downplayed the risks of salmon aquaculture to wild salmon in BC. Part of the problem has to do with the limited scope of the research conducted by CSAS, which has been based on a relatively smaller number of salmon production sites and relatively fewer salmon species. Krkošek et al. consider all salmon species in BC and all regions where salmon is farmed.

However, the bigger concern is that CSAS scientific research may have been influenced by industry players’ intent on watering down the risks of aquaculture to wild salmon species. Over the last decade, several official government reports have been published raising questions about the integrity of CSAS science. One team of scientists pointed out that the quality of science advice to DFO has “repeatedly been a cause for concern among scientists, nongovernmental organizations, Indigenous groups, and even government bodies” (3). A long-recognized paradox in the regulation of salmon aquaculture in BC and elsewhere in Canada is that DFO’s mandate is both to promote aquaculture production and, at the same time, to protect wild fish species including salmon. The promotion of ocean net-pen aquaculture and the protection of wild species are incompatible.

Nevertheless, important regulatory changes in BC for salmon aquaculture have occurred. For example, licenses for salmon aquaculture were not renewed in three coastal regions of BC that are critical to wild salmon migration routes. The closure of these farms was significant, constituting almost half of the province’s farmed salmon production. These recent closures should be seen in the context of a broader commitment to phase out open net-pen aquaculture announced by the federal government in 2019. Details on the transition plan were announced in June 2024, when regulators released a timeline for phasing out open net-pen aquaculture in BC (3). Under this plan, existing licenses for open net-pens will be renewed to 2029, at which point all open net-pen aquaculture in BC will be banned. Acknowledging the concerns of environmental groups and scientists, these renewed licenses will be governed by much stricter environmental conditions and monitoring. New licenses for farming salmon in BC will be considered, but only for closed containment systems on land and in the ocean. As an incentive to industry, and in recognition of the likely investments required for closed containment technologies, these new licenses will be granted for 9 years.

The decision to ban open net-pens in BC was long awaited, but also highly significant. Open net-pen salmon farms will be banned in recognition of the threat they pose to wild salmon in BC. Through this decision, BC joins Washington State in banning Atlantic salmon aquaculture using open net-pen technologies (4). The phase out process in BC has already started with the announcement that existing land-based hatchery licenses are being renewed for 9 years. There is also news that a Norwegian company is partnering with a BC First Nation group to apply for a closed containment license for farmed salmon (5). The transition from open net-pen aquaculture in BC is clearly well underway.

Uncertainties, of course, exist on what the transition will look like, and headwinds are blowing as some industry players in BC remain wedded to open net-pen aquaculture. The largely foreign-owned companies that operate in BC and their employees have contested the transition plan arguing that it will lead to job losses and will discourage investment in the sector. Environmental groups, on the other hand, who support the ban are worried that it may be vulnerable to changes in government and are calling for legislative measures to future proof the decision to transition away from open net-pen aquaculture (6). In addition, it is unclear what closed containment will encompass given that regulators are allowing this form of production to occur on land as well as in the ocean. In Norway, for example, current technology for closed containment is often focused on massive scale production systems in deep water sites (7), which raises questions about regulatory oversight (8) and environmental sustainability (9, 10). Despite these uncertainties and political headwinds, the decision in BC to shrink the salmon industry’s footprint, supported by rigorous scientific analysis, underlines the unacceptable environmental burden of an infrastructure that has for so long supported industrial salmon farming.