Farmed Atlantic Salmon: A Life Not Worth Living?

Salmon are the most farmed fish in Europe and are among the most expensive in the world – their economic value amounts to 18.1% of global fish trade value, yet they make up only 2.8% of global aquaculture. Consequently, salmon aquaculture is one of the most well-researched fish farming systems due to their outsized economic value and tendency to be located in wealthier countries. However, there still exist many welfare knowledge gaps for farmed salmon, and the welfare understanding of salmon may be useful in addressing welfare issues for other species of farmed fishes. While farmed fish welfare might not be a significant concern to consumers, as we’ve covered in a different post, there is some promising evidence that some consumers are willing to pay more money to ensure higher welfare standards for farmed fish.

A recent report published by the Fish Welfare Initiative identified key welfare issues in Atlantic salmon farming operations and suggested future research directions. The main findings of the report were:

• Salmon fare very poorly in farming operations and do not have a ‘life worth living’ under criteria specified by the Farm Animal Welfare Council;
• Sea lice infestations of Atlantic salmon farming operations pose an existential threat to both salmon farms and nearby wild salmon populations;
• Farmed salmon feed consists of other fish and poultry meal, compounding animal welfare issues in the supply chain;
• Slaughter methods of terrestrial animals have been adopted in the salmon farming industry, yet may not be the most humane slaughter methods for fish; and
• Research is required to determine if preferred behaviors in salmon can be triggered in aquaculture operations.

While the sentience of fishes is unfortunately still debated among the general public, the welfare of farmed fishes represents a particularly important issue for animal advocates who want to make a positive impact in the lives of millions of animals. Below, we take a close look at the FWI report, and offer supplemental resources wherever possible.

Confinement Rules Out a ‘Life Worth Living’

The ‘Five Freedoms’ have been used for decades to measure the quality of life of farmed animals, and they’ve been implemented with varying degress of success. We’ve also covered studies about the Five Freedoms extensively in our library. As outlined by the Farm Animal Welfare Council, the criteria for a farmed animal to enjoy a ‘life worth living’ are:

1. Freedom from hunger and thirst;
2. Freedom from environmental challenge;
3. Freedom from disease and injury;
4. Freedom from behavioral restriction; and
5. Freedom from mental distress.

Atlantic salmon farms may meet the first criteria, but the report details how farming operations do not satisfy the remaining requirements for a ‘life worth living’. Of special note is the failure to satisfy the fourth requirement, freedom from behavioral restriction, which Compassion in World Farming highlights as the main reason to deem Atlantic salmon ‘fundamentally unsuitable for farming’. Potentially related to this restriction, we’ve covered a study that suggests farmed salmon are depressed from chronic stress in the farm environment.

Atlantic salmon are migratory animals, with ranges of over 9,000 km. Thus, their confinement in farms is incompatible with their natural drive to swim and cover vast distances.

Not only that, Atlantic salmon are solitary animals and naturally would not encounter many other Atlantic salmon during most of their adult life. However, in Atlantic salmon farms, they are stocked in open-net sea cages at densities of 10-25 kg/m³. Both low and high stocking densities on Atlantic salmon farms present negative welfare outcomes. These fish have a dominance hierarchy, and during their young adult phase (known as smolts) they are known to attack and cannibalize smaller smolts. Surprisingly, lower stocking densities result in increased aggressive behavior and cannibalism among smolts due to the dominance hierarchy. Higher stocking densities are associated with low dissolved oxygen availability, decreased growth, reduced nutritional uptake, fin and gill damage, immunosuppression, and aggression. The report cites one welfare specialist who believes that the only reason aggressiveness is lower at higher stocking densities relative to lower densities is that schooling behavior — otherwise abnormal smolt behavior that is commonly observed in farms — is merely a response to confinement stress.

Stopping Sea Lice: The Only Alliance Between Welfare and Economic Interests

Another negative welfare outcome of confinement and unnaturally high density is the increased rate of infectious diseases, among them being pancreatic disease, cardiomyopathy syndrome, and infectious pancreatic necrosis. However, sea lice infestation is the primary disease threat to Atlantic salmon, and the issue is so severe that it poses an existential threat to the Atlantic salmon farming industry. We’ve previously covered aquaculture’s sea lice problem in an earlier post.

Sea lice are parasites that thrive in open-net farms because of the high density of hosts, which allows sea lice populations to exceed levels that salmon are adapted to deal with; infection pressure for sea lice is 70 times greater near salmon farms. Sea lice feed on salmon skin, causing scarring, infections, fin loss, and death. Sea lice can be especially fatal to juvenile salmon, who are not adapted to deal with sea lice because they naturally do not encounter adult fish until later in their lives. Since most open-net salmon farms are located in tidal estuaries that intersect with migratory routes of juvenile wild salmon, sea lice infestations also threaten wild salmon populations. Wild salmon on the west coast of Scotland face extinction-level population collapse, evidenced by record-low catches of wild salmon in those areas.

Current methods to manage sea lice infestation include insecticide use and thermal delousing. However, sea lice are becoming increasingly resistant to insecticides, leading to the preference of thermal delousing as an alternative. Thermal delousing involves pouring hot water (28-34° C, or 82-93° F) on salmon to remove sea lice, but “thermal delousing causes panic behavior and increased salmon mortality, and that treatment is likely to be painful” according to Susanna Lybæk of the Animal Protection Alliance. The salmon farming industry is exploring the stocking of other fish species in salmon farms, such as wrasse and lumpfish, to feed on sea lice; however, there are additional welfare concerns that would arise from farming these other fish, such as maladaptive aggression, disease, and the fact that salmon would prey on these other fish species intended to reduce the suffering of salmon. 

A more promising solution to sea lice infestation would be to operate open-net farms in colder or deeper waters where sea lice are not adapted to survive. Another solution would be developing lifelong inland salmon farms, in which freshwater and saltwater are recirculated to keep the farm environment free of sea lice. Of course, both such solutions take for granted that salmon farming will continue, and given the demand for fish products around the world, this is an unfortunately likely scenario for the foreseeable future.

Sea lice aside, Atlantic salmon farming still poses existential risks to ecosystems of wild salmon if feedlot nets are breached, commonly by storms or predators such as seals. We’ve covered a study on escaped farmed salmon in an earlier post. The gene pool of farmed Atlantic salmon is limited, and escaped farmed salmon can interbreed with wild populations, resulting in decreased adaptation and resilience to specific habitats, population numbers, and genetic variation.

An Entire Web of Suffering

Salmon are both apex predators and obligate carnivores. Carnivorous fish are the only obligate carnivores that are commercially farmed at large scale, and carnivores are ill-suited for farming because of aggressive behavior and higher cost of feed required — salmon feed is a mixture of farmed fish, wild-caught fish, fish offcuts, chicken, and turkey. The FWI report states that one-third of all caught fish ends up being used as animal feed, which is similar to a finding from another report we’ve previously covered that found one-fourth of caught fish end up in non-food production and animal feed. Poultry meal can make up about 30% of farmed salmon feed. Production of salmon requires the sourcing of meat for feed, thus intertwining salmon farming ethically and economically with welfare issues in the farming and slaughter of other species.

Inhumane Slaughter

Farmed Atlantic salmon face myriad welfare concerns leading up to and at slaughter. The process of rounding up salmon for transportation and slaughter is called net-penning, and it’s something we’ve covered previously in our library. Fish can be starved for up to a month before slaughter. Some commercial benefits of starvation include preserving water quality during transport by reducing excrement production, more sanitary carcass processing since guts are empty, and prolonging the route to market for fish when the market is weak. Transport and slaughter environments typically use recirculated water, so there is also the concern of carbon dioxide and ammonia buildup in the water.

Many slaughter methods used for farmed Atlantic salmon are objectionable from a welfare standpoint because suffering persists for a long period of time. Carbon dioxide dissolution into water to create carbonic acid causes an immediate aversive reaction to the acidic environment, and full brain activity is present during the several-minutes-long death. Air asphyxiation takes even longer, often over an hour, to kill salmon. Live chilling is a variation of asphyxiation conducted using ice, and may result in death faster than air asphyxiation. 

Currently, the most recommended slaughter method is stun-bleed, in which salmon are 1) stunned, usually through percussive means with a pneumatic rod or by manual clubbing with a metal rod, and then 2) immediately exsanguinated, or cut for bleeding to death. This slaughter method has been appropriated from terrestrial animal slaughter for its efficacy as a “high-welfare” technique for terrestrial animals, but there is poor evidence that this effectively translates to fish. Electrical brain activity monitoring of salmon during stun-bleed shows that it can take several minutes for brain activity to stop following exsanguination. Not only that, but it is uncommon to check if fish have actually been rendered insensible after stunning, so it is questionable if this slaughter method would provide its theoretical high-welfare benefit in practice.

A more humane slaughter technique may employ electrocution, which has a high rate of successful stunning, but this method has yet to achieve widespread commercial application. We’ve also posted about an experimental salmon slaughter method using carbon monoxide to investigate the stress response induced in salmon compared to percussive stunning.

Triggering Preferred Behaviors in Farm Environments

The industry is looking into lifelong inland environments for salmon farming, also called land-based salmon aquaculture or recirculating aquaculture systems. This would involve moving juvenile salmon from an inland freshwater recirculating system to an inland saltwater recirculating system, and raising them to harvest weight without ever being at sea. Welfare benefits would include the absence of sea lice infestations and the ability to closely monitor and control dissolved oxygen levels and crowding. The wider ecosystem benefits include reducing the impact of sea lice infestations, insecticide exposure, excrement pollution, and genetic dilution on wild salmon populations. However, land-based salmon aquaculture still does not address welfare concerns related to slaughter methods, other animals in salmon feed, and salmon-preferred behaviors.

Comprehensive studies on wild salmon behavior are lacking and more study is needed to understand the psychological consequences of depriving salmon of their innate migratory behavior. Other behaviors with welfare components must also be identified. Additionally, it must be studied whether these behaviors have triggers that can be emulated in captivity. If not, it may be that the only humane alternative to open-net fish farming is to harvest Atlantic salmon from extrinsic, open ecosystems where care is taken to maintain salmon populations at high enough levels to support economically sustainable harvests.

Significance Beyond Farmed Salmon and Outlook

The report concluded with recommendations on future research areas and solutions to welfare issues faced by farmed Atlantic salmon. These recommendations offer researchers and advocates many possible avenues for future work, including:

• Sea lice: Research impacts on wild salmon populations, and locating open-net farms in colder, deeper waters. Potential solutions include pesticide alternatives, reducing stocking densities, and enacting regulations on open-net farm siting.
• Water quality: Research dissolved oxygen enhancement in oxygen-deprived areas of open-net sea cages, and dissolved oxygen management in inland salmon farms. Potential solutions include using aerators in open-net sea cages.
• Use of cleaning fish: Research welfare requirements of wrasse and lumpfish in salmon farms. Potential solutions include reducing or eliminating their use by using alternative delousing solutions.
• Slaughter welfare: Research the use of electrocution in stun-kill method, and investigate electrical brain activity of various slaughter methods. Potential solutions include promoting the use of higher-welfare slaughter methods based on species-specific evidence.
• Preferred behaviors: Research which behaviors have welfare components and if these can be triggered in captivity. Potential solutions include developing unconfined aquaculture systems, creating salmon breeds that fare better in captivity, and transitioning salmon farming to a different fish species better suited to confinement.
• Stocking density: Research temporal and spatial distribution of salmon in open-net sea cages, and how stocking density affects salmon interaction with symbiotic species. Potential solutions include transitioning to the lowest density that minimizes aggressive behaviors, likely 10 kg/m³.
• Mortality: Research improved methods of inducing smoltification, and mortality rates of cleaning fish in salmon farms. Potential solutions include using individual fish progression tracking technologies, such as microchipping.
• Welfare in feed: Research welfare issues for other animals in the salmon feed supply chain, and develop more efficient feed. Potential solutions include promoting low-impact food standards, and replacing caught fish with offcuts in salmon feed.

For animal advocates, the report paints a comprehensive picture of the overall welfare of farmed Atlantic salmon, and the picture is quite grim. Providing these complex creatures with proper welfare will be a gargantuan undertaking, and will require cooperation between industry and governments, as well as keeping open lines of communication with advocates and animal behavior specialists who have the salmons’ best interest at heart. For many animal advocates, the farming of wildlife is something to be challenged in and of itself; for advocates working to improve conditions in the meantime, FWIs report, and the many other studies cited here, provide a roadmap forward.