Summary: Farmed salmon contains high levels of saturated fat, and more calories than wild salmon. It can also be contaminated with microplastics, chemicals from their feed, and antibiotic-resistant bacteria, posing risks to both consumers and ecosystems. With certifications offering limited protection and misleading “organic” labeling, the significant health and environmental concerns surrounding farmed salmon warrant careful consideration.

Farmed salmon is marketed as a healthy choice, a better alternative to beef, pork and poultry¹. But questions about its nutritional value and farming-related contaminants like microplastics and antibiotics have farmed salmon under increasing scrutiny.

Nutritional profile: More fat, fewer benefits

Farmed salmon contains troubling levels of saturated fat – more than double² that of wild salmon. A fillet of farmed salmon also has more calories and overall fat than its wild counterpart.

While it may boast higher omega-3 fatty acid content due to artificially enriched feed, the Cleveland Clinic warns³ that this benefit is overshadowed by the risks associated with its elevated saturated fat, which can contribute to heart disease.

‍Antibiotic Resistance: A Growing Global Threat

The widespread use of antibiotics in salmon farming raises red flags for global public health. Indiscriminate use of antibiotics can lead to the bacteria developing resistance to the drugs, which poses a direct threat to human health by eroding the effectiveness of the medicines we rely on. Resistant genes from aquaculture bacteria can transfer to human pathogens⁴, increasing the risk of people becoming infected with untreatable “superbugs.”

Farmed salmon are often raised in overcrowded, unsanitary conditions that breed disease and necessitate antibiotic use⁵. The Chilean aquaculture industry in particular is known to use lots of antibiotics - more than 338 metric tons in 2023, according to the New York Times⁶ - and efforts to reduce their use have had mixed results. Norway, on the other hand, reported almost no antibiotic use on salmon farms in the same year.

Although many countries attempt to strictly control the use of antibiotics in aquaculture, the industry is not always honest about how much they use. The Scottish salmon aquaculture industry association reported using just 940 kilograms of antibiotics in 2024, which it said was the lowest number ever. But they were forced to revise that number upwards, to 1,564 kilograms, after an investigation by Scottish journalists⁷ - which “seriously undermines” the industry’s credibility, according to one Scottish politician⁸.

The link between antibiotic use on fish farms and growing resistance among bacteria is clear. One 2024 study found that Chilean salmon farms, for example, are hotbeds of antibiotic resistant bacteria⁹, and similar trends¹⁰ have been seen near fish farms in Canada’s Bay of Fundy. Global warming is likely to exacerbate this crisis¹¹ by increasing disease and death in sea cages, thereby driving up antibiotic usage and further accelerating the spread of resistance.

Microplastics: A widespread contaminant

Microplastics are a pervasive contaminant in farmed salmon. Tiny plastic particles have been found in the gills¹² and fillets¹³ of farmed salmon.

Microplastics can also be found in wild salmon, but farmed salmon may be at greater risk of absorbing them because their food and the cages they live in are themselves sources of microplastics. Plastic has been found in the vast majority of commercial fish meal¹⁴ that makes up the bulk of the diet of farmed salmon. Plastics also get into the water in sea cages from the abrasion and degradation of ropes, nets, and floats¹⁵, and as the result of friction in plastic feed pipes¹².

This exposure to microplastics weakens fish, increasing mortality rates in trout when combined with viral infections¹⁶, according to research from the National Institute of Standards and Technology. Another study from Norway found that while exposure to microplastics in their diet did not affect survival and growth of salmon smolt, it did have a variety of toxic effects on the fish, including damage to cells, DNA, and metabolic problems¹⁷.

Evidence that microplastics may also pose a threat to human health¹⁸ is growing. A recent review of scientific publications concluded that they are suspected to “harm human reproductive, digestive, and respiratory health, with a suggested link to colon and lung cancer.”¹⁹

Chemical Contaminants: a lingering problem?

In the past, farmed salmon were often contaminated with dangerous levels of harmful chemicals²⁰ such as polychlorinated biphenyls (PCBs) and dioxins, which came from the fish oils found in their feed. Changes in the composition of feed brought in by the aquaculture industry in the early 2000s has led to a drop in these contaminants²¹ in the years since.

But it is an issue that is worth keeping an eye on, since these chemicals are long-lasting, can accumulate up the food chain as predators eat contaminated prey, and their negative health effects in humans are well-known²². And one recent study found that microplastics can bind to the persistent organic pollutants associated with salmon farming²³, providing another potential route for the contamination of farmed fish.

Label this ‘confusing’

It is difficult to find out what has gone into raising farmed salmon due to the lack of transparency in labeling and the use of misleading labels.

There is no such thing as “organic” salmon (or any fish) in the US, because the Department of Agriculture (USDA) does not set specific standards for "organic" salmon²⁴. Canada²⁵ and the European Union²⁶ do have organic standards for salmon, however, so US consumers may often see these labels on imported products. This complicated labelling situation can be confusing for shoppers looking for the healthiest and most sustainable options.

Relying on the advice of consumer guides from the Aquaculture Stewardship Council²⁷ and Seafood Watch²⁸, which focus on the sustainability of aquaculture practices, is of limited usefulness. As a 2024 article in The Washington Post advised²⁹, “While these certifications can be a good indication that your fish is sustainable, don’t rely on them.” This is because current guidelines are far from complete and could be misleading³⁰.

In 2023, for example, the Icelandic fish farming company Arnarlax was ordered to stop using sustainability claims in its marketing and branding materials³¹ by the country’s consumer agency.

The lack of a requirement for farm-of-origin or farming method labeling allows consumers to unknowingly purchase salmon from producers that have a history of regulatory and legal violations and ongoing biological challenges, even in highly regulated, “safe” countries like Norway. And “product of” labels only provide the country where the fish was last “substantially transformed,” not necessarily where it was farmed.

Each third-party certifying body also uses different standards³², often focusing on specific environmental sustainability aspects while neglecting critical issues like antibiotic resistance, microplastic contamination and the use of harmful chemicals.

The lack of clear, comprehensive labeling not only undermines consumers’ ability to make informed decisions about their food but also enables producers to confuse consumers.

As a result, one 2022 study³³ found that “many producers and retailers” have even stopped labeling salmon as “responsibly farmed” in the UK and only use certifications such as the ASC standard internally.

It concluded that “unresolved environmental challenges of salmon farming, combined with perceived weaknesses in the ASC salmon standard, have led not only non-governmental organizations but also several major retailers to view the ASC as not setting the bar high enough to enable salmon farming to be defined as ‘sustainable’.”