How fish farming is devastating marine life with a single salmon consuming up to 350 wild fish

Early summer on Scotland’s most northerly island of Unst, Shetland. Gannets, fulmars and puffins patrol the cliffs, their calls echoing over slopes dotted with sea pinks. But beneath this vibrant scene lies a troubling truth: seabird breeding failures that have coincided with the presence of industrial fishing trawlers offshore.

It was 30 years ago when I first discovered that the phrase “there’s plenty more fish in the sea” couldn’t be trusted. Those fish in the sea are finite. And if we carry on as we are, seabirds won’t be the only ones facing trouble.

There has been welcome progress since then, not least the Scottish Government’s recent ban on sandeel fishing in all Scottish waters, including those in the North Sea. The decision was made to protect marine biodiversity and align with national and international commitments to environmental protection.

READ MORE: UK-EU fishing deal branded 'biggest act of betrayal' to Scottish fishermen

Salmon, known as the 'King of Fish', are natural wanderers who should not be forced to swim in circles like caged tigers endlessly pacing around their enclosure (Picture: Jeff J Mitchell) | Getty Images

Third of all sharks face extinction

However, the backdrop is that human activity continues to steadily drain the life out of the ocean. We are plundering the seas faster than the fish can replicate.

At the recent United Nations’ Ocean Conference in Nice, a statistical ‘catch of the day’ was showcased: that more than a third of the world’s fish are harvested unsustainably. Pushed beyond their biological limits. More than a third of all sharks and rays are now at risk of extinction because of overfishing.

In 1883, scientist Thomas Huxley notoriously declared that “all the great sea fisheries are inexhaustible” and that “nothing we do seriously affects the numbers of fish”. More than a century on and it has become abundantly clear he was wrong.

READ MORE: Jellyfish blamed for deaths of 200,000 Scottish salmon

The damage done by overfishing goes beyond the marine environment. Billions rely on fish for protein, and fishing provides livelihoods for millions of people around the world.

As wild fish stocks dwindle, fish farming is often touted as the solution. But far from easing the burden on our oceans, it may be compounding the crisis.

Farming of carnivorous fish species like the salmon farming found along the west coast, the Highlands, and Northern Isles, is wrongly seen as a solution to declining wild fish populations.

That’s because vast quantities of fish are being caught from the wild simply to feed farmed fish in what is a wasteful process – a single farmed salmon can take about 350 wild fish to produce. By continuing to feed wild-caught fish to farmed fish, we are taking away an essential layer in the food chain, thereby undermining the future for the oceans.

READ MORE: Why oysters, the natural world's 'marine engineers', are vitally important to Scotland's seas

Eroding marine ecosystem’s foundations

Today, about a fifth of the world’s fish catch is used as animal feed, being fed to farmed chickens, pigs, and fish. Anchovies, sardines, and herring are the main species targeted by the industry, with supplies often sourced from as far off as South America and Africa.

These wild fish tend to be the foundation of the marine ecosystem, providing food for puffins and other seabirds, as well as feeding the bigger fish that we like to put on our plate. In total, they would be enough to provide a billion more people with a dietary supply of fish, while leaving them in the ocean would take huge pressure off hard-pressed fish stocks.

In Scotland, fish farming has grown from just a couple of sites about 50 years ago to more than 200 today. It now feeds as much wild-caught fish to its salmon as is eaten by the entire UK population. The industry has been described as Scotland’s ‘new oil’, but like petrochemicals in the context of climate change, it’s seriously in need of an urgent rethink.

Intensively farming what are essentially wild fish species like salmon also raises serious animal welfare concerns. Salmon are farmed in large sea cages anchored along the coast, with each fish having the equivalent of a single bathtub of water.

Swimming in circles

Yet, these are natural ocean wanderers. Which is why huge shoals of farmed salmon swim in incessant circles, showing behaviour reminiscent of caged tigers pacing their enclosures out of frustration.

Like the environmental impact, welfare conditions for farmed fish are often out of sight, out of mind. Hidden below the depths. However, from time to time, investigations bring home what life can really be like for the incarcerated ‘king of fish’.

One such example in recent years was by a diver who took to the icy waters off the west coast of Scotland, Skye and Shetland to uncover salmon farming’s hidden side.

Farmed salmon were found with diseased and swollen gills. One swam in a bit of a daze, with eyes missing and sockets red raw. Some had chunks out of their bodies and gaping wounds, while others had seaweed growing from their injuries, as if they were rotting alive.

Industrial fish farming often causes serious concern for animal welfare and is central to a ravenous fishmeal industry. The true impact on iconic wildlife and the ecosystem we all depend upon is only just coming to light. Some companies involved are starting to make changes, but much more needs to be done.

Consumers can help by buying wild fish from sustainable stocks, preferably line caught. If buying farmed fish, then ensure that it comes from a certified organic supplier.

There remains a chance to take action – but only just. As oceanographer Sylvia Earle warns, “there is still time, but not a lot”. The choices we make now will determine whether future generations inherit thriving seas – or empty ones.

Philip Lymbery is chief executive of Compassion in World Farming, president of EuroGroup for Animals, and a UN Food Systems Advisory Board member. His latest book is Sixty Harvests Left: How to Reach a Nature-Friendly Future. Philip is on X @philip_ciwf