Salmon is becoming increasingly popular, but ever since the former delicacy became a mass product, new problems have emerged. Until the 19th century, most salmon species were widely available. Due to the growing demand, salmon was caught in ever larger quantities, so that natural salmon stocks declined sharply over the course of the 20th century. Wild salmon became scarce and farmed fish an alternative.

At the end of the 1970s, salmon began to be bred in aquacultures in Norway and elsewhere. This made salmon available again in larger quantities and, above all, all year round. If you take a closer look at the packaging, you can see that many of the salmon come from such aquacultures.

Salmon farms are booming because the meat of the fish is popular. The fish are usually kept in huge enclosures in aquacultures and fattened until they are ready for slaughter in two to three years. A study shows that farmed Atlantic salmon are just as fertile as wild salmon, despite many genetic differences.

The farmed salmon business has grown strongly over the last 40 years, from Norway to Scotland to Canada and Chile. According to the FAO, global production in 2021 will be around two thousand times higher than wild salmon catches. This means 2.9 million tons of farmed salmon compared to 1,500 tons of wild salmon.

One of the new problems arises when farmed salmon mate with wild salmon. The offspring could affect the genetic diversity of wild stocks. Farmed salmon are bred for certain genetic traits, for example they reach sexual maturity a little later in order to grow longer.

Again, this raises the question “Are farmed salmon a threat to wild salmon?” The answer is: possibly yes.

Salmon lice cause extensive damage

The salmon louse is one of the biggest threats to salmon farms and causes great damage. The salmon louse is a small crustacean that lives on the skin of the fish and feeds on its mucus, skin and blood.

Salmon lice are so devastating for aquaculture because many salmon are kept in relatively confined spaces in net pens. This means that parasites can move more quickly from one salmon to another and infect the entire stock.

As salmon lice are naturally occurring parasites, there were already high parasite-related losses in the early days of salmon farming, so that promising solutions have been sought ever since.

Farmed salmon from aquafarms also pose a threat to their wild counterparts in other ways. Aquaculture farming not only increases the potential parasite pressure within the facility, but also the pressure on natural populations of wild fish. If aquaculture facilities are located close to natural salmon migration routes, this can affect entire populations. Young salmon in particular are at risk on their migration to the sea.

Escaped salmon are the biggest threat

In Iceland, around 3,500 salmon escaped from an aquaculture facility in mid-August 2023. The fish are fully grown and sexually mature. When they mate with wild salmon in rivers, they weaken their population. This results in hybrids that are less well adapted to this environment and reproduce less well. This threatens the wild stocks and they could be decimated as a result.

The company involved is Arctic Fish, which operates nine farms in four fjords in the Westfjords region. Two Norwegian divers are now in the Ísafjarðará river to search the riverbed for farmed salmon and kill them with a harpoon. The divers have been sent by a Norwegian company, because in Norway more than 100 rivers are scoured in this way every year to clean them of farmed salmon and such fishermen have long been part of the business.

Since the outbreak at Arctic Fish, 500 farmed salmon have already been officially caught from various rivers. “It’s a nightmare that we’ve been warning about for years,” explains Elvar Fridriksson. The 34-year-old heads the North Atlantic Salmon Fund a small NGO in Reykjavik that has been dedicated to the fight to protect the Atlantic salmon since 1989.

Mass exodus in Chile

The incident in Iceland is not an isolated case. The escape of 690,000 salmon from a farm near the southern Chilean city of Calbuco on July 8, 2018 drew attention to the environmental problems of the multi-billion dollar salmon industry. Apparently, a thunderstorm had destroyed some of the farm’s cages, at least according to the official account.

The problem: the animals had been treated with a total of around two tons of antibiotics, which posed a risk to humans and other living creatures. Up to 700 times more antibiotics are used in Chile than in other countries such as Norway. The reason: fish diseases are more widespread in Chile than in other countries.

The plant belongs to the Norwegian company Marine Harvest, the global market leader for farmed salmon. Such incidents occur from time to time in the industry, but rarely at this scale. The authorities spoke of the largest fish escape in Chile’s history.

Salmon are not native to the southern hemisphere. Ecologists therefore feared serious consequences for other species. The greatest danger to the ecosystem is probably the sheer number of an alien species suddenly swimming around freely.

Norway – 49,000 farmed salmon on the run

On July 7, 2019, around 49,000 farmed salmon escaped through a hole in the net from a facility in the Tosenfjord south of Brønnøysund. The company had offered a reward of 300 kroner per fish for the catch. Of the fish from the facility in the Tosenfjord, only 418 salmon were recaptured 6 days after the escape.

Andreas Johansen from Bindal and his friends seized the opportunity and caught 120 salmon by Thursday after the escape. This resulted in a nice bounty of 36,000 crowns (3,200 euros). Johansen’s brother also went hunting for “fugitives” and also caught over 100 salmon.

The opportunity to escape apparently arose during a mechanical measure to remove the salmon lice. The Norwegian Fisheries Agency is extremely reluctant to see such mass escapes, as the genetic mixing of wild and farmed salmon is undesirable.

Around 160,000 salmon escaped in 2018

Although it is rare for so many fish to escape at once, it does happen from time to time. According to statistics from the fisheries authority, 160,000 farmed salmon managed to escape in 2018. 54,000 of these came from the same company, as they managed to escape on the same day. According to the statistics, 1,200 of these were recaptured.

Heiner Kubny, PolarJournal

More about this topic