Skip to main content

Salmon Farming's Dirty Secret

I've spent half a century writing for radio and print (mostly print). I hope to still be tapping the keys as I take my last breath.

Two Sides of Salmon Aquaculture

Once a treat that only the wealthy could afford, salmon is now on everyman's dinner plate. To a large extent, the fish is affordable because of salmon farming. But, there are downsides.

Salmon—our favourite fish.

Salmon—our favourite fish.

Decline of Salmon Stocks

Writing for The Globe and Mail in July 2022, journalists Catherine Collins and Douglas Frantz noted that “In recent decades, wild Atlantic and Pacific salmon have almost disappeared from Canada’s rivers and oceans—victims of habitat destruction, overfishing, and climate change.”

Business Intelligence for Vancouver tells us that “Global abundance of Pacific salmon in 2020 was the lowest it has been since 1982 . . . Russia. . . saw its commercial catch fall from 600,000 tonnes to 400,000 in 2020 . . .” Additionally, “The total North American catch (Alaska, Canada, Washington, Oregon, and California) was 252,000 tonnes, which was the lowest since 1977.”

Here's the BBC “Wild salmon is no longer fished commercially anywhere in the UK.”

The decline in salmon stocks is global and the villains that take the blame are climate change and overfishing. Yet, consumers are eating more salmon than ever before, three times more than in 1980, and that's because of the massive growth in salmon farming worldwide.

Salmon Farming

In the 1960s, Norwegians started experimenting with salmon farming. It seemed like a great idea. Instead of chasing the elusive fish around the ocean in boats, it made sense to raise them in ocean pens where they could be harvested with ease.

Today, there are more than 100 salmon farms on the coast of British Columbia, Canada alone, making that country one of the world's largest producers of farmed salmon. Other big players are Norway, Chile, and Scotland with more than 200 farms.

According to the World Wildlife Fund, farmed salmon now accounts “for 70% (2.5 million metric tons) of the market.”

The most commonly farmed species is the Atlantic salmon and they are raised intensively with up to half a million fish in a single cage.

Sentient Media describes the life cycle: “Farmed salmon begin their lives in hatcheries. When they are born, they are raised in freshwater tanks for up to two months. After a year or so, they are transferred to sea cages, where they are fed commercially-produced fish food often made of wild-caught fish.” The process from hatching to table takes about three years.

Atlantic salmon fish farm, off Denmark's Faroe Islands, north of Scotland.

Atlantic salmon fish farm, off Denmark's Faroe Islands, north of Scotland.

Feeding Farmed Salmon

In the wild, salmon eat plankton, algae, insects, crustaceans, and other fish, but, when hundreds of thousands are crammed into a seawater cage, there's not enough natural food to go around.

Journalists Catherine Collins and Douglas Frantz discovered the fish at farms in Nova Scotia “are fed pellets of ground fish meal, poultry by-products such as feathers and feet, and vegetable ingredients.” Chicken feathers? Not normally part of the diet of salmon.

The feed is also laced with antibiotics to combat disease among the closely packed animals. Unconsumed feed sinks to the bottom, along with enormous quantities of excrement, and build up into a noxious pile under the cages. This kills any marine life unwise enough to get near it.

The conditions in which farmed salmon live contribute to a high death rate among the fish. The BBC reports that “Every year about 9.5 million fish die in the salmon farms, about 20 percent of the total.” People in the cattle-raising business see fatality rates of 3.3%, for chicken farmers the rate is five percent.

Salmon confined in a pen swimming in a circle.

Salmon confined in a pen swimming in a circle.

The Problem of Sea Lice

Seal lice are small crustaceans that feed on fish. In wild conditions, the lice are not a major problem, but, when salmon are confined in a pen the concentration of sea lice grows rapidly. They feed on the flesh of the fish, quite literally eating them alive.

People in the aquaculture business use chemicals, called parasiticides, to deal with sea lice infestations. However, Atlantic Ocean sea lice have become more resistant to the chemicals so more toxic formulations are used. The same resistance has been noted among sea lice in British Columbia. The chemicals, of course, don't stay in the cages and have negative impacts on wild fish populations such as crabs, and lobsters.

One study on Canada's East Coast found a banned chemical, Cypermethrin, in dead crustaceans. Environment Canada charged one aquaculture business with releasing toxic substances into the sea. This resulted in a $500,000 fine. Other salmon farmers have likely used the same chemical and not been detected.

Adult salmon can tolerate hosting parasitic lice, but young fish can't. So, when newly hatched salmon smolts out-migrate past salmon farms, the sea lice in the pens latch onto them. The young fish can't fend off the assaults on them and die.

Some Nasty Stuff Found in Salmon

Sentient Media has published an alarming list of substances found in farmed salmon:

  • Salmon farmers use thousands of tonnes of antibiotics. Residues in the flesh make antibiotics less effective when prescribed to people to fight infections;
  • Synthetic canthaxanthin is fed to salmon to make its flesh pink. This chemical has been linked to vision loss and hyperactivity in children;
  • A study found that “organic arsenic was significantly higher in farmed than in wild salmon, whereas cobalt, copper, and cadmium were significantly higher in wild salmon;”
  • Farmed salmon are lower in iron and calcium and higher in protein, fat, sodium, and fatty acids than wild salmon;
  • “The World Health Organization website cites a journal dated in 2004 which found a significant presence of PCBs and dioxins in farmed salmon. More recent studies on Norwegian Atlantic salmon, Japanese masu salmon, and fish feed in Europe indicate the presence of PCBs and dioxins, suggesting that these pollutants have accumulated in salmon farms over the years.”
Sockeye salmon ready (almost) for the table. Let's hope the PCB count is low.

Sockeye salmon ready (almost) for the table. Let's hope the PCB count is low.

Is Farmed Salmon Safe to Eat?

Doctors tell us that we ought to be eating oily fish such as salmon so as to load up with heart-healthy omega-3 fatty acids. Two servings a week is the recommended quantity.

Catherine Collins and Douglas Frantz, who we met earlier, are the authors of the 2022 book Salmon Wars. They have written for Time magazine that “Some studies warn that a single meal per month of farmed Atlantic salmon can expose consumers to contaminant levels exceeding standards from the World Health Organization. The risk is greatest for infants, children, and pregnant women because of the potential harm from contaminants to developing brains.”

The debate continues and consumers are left guessing. The best advice seems to be buy wild salmon if you can find it and limit consumption.

The completely different issue of the environmental impact of salmon aquaculture may cause some consumers to stop eating salmon altogether.

Bonus Factoids

  • It's believed that 200,000 years ago, Neanderthals ate salmon. The Romans built ponds in which to keep salmon fresh.
  • Norway's Mowi ASA is the world's largest operator of salmon farms. In 2021, the company was found guilty of misleading advertising in a U.S. court. Mowi agreed to pay a fine of $1.3 million and promised to stop using phrases such as “sustainably sourced, all-natural and caught in Maine” in promoting its products.
  • The Canadian government has announced that all open-net salmon farms on the British Columbian coast will be shut down by 2025. The plan is to transition the industry to land-based systems that use recirculated water. B.C.'s salmon farmers are lobbying to get the decision reversed.
  • Fish meal is one of the ingredients fed to farmed salmon. This comes, of course, from fish caught in the oceans. The authors of Salmon Wars, say that meeting the “growing global demand for salmon, huge trawlers pillage the fisheries off the coast of West Africa and Peru, robbing subsistence fishers of their livelihood and increasing food insecurity..”


This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Rupert Taylor