Adverts on the London Underground, shared by animal activist group Project Slingshot, have been warning of 'toxic chemicals' and sea lice in farmed salmon, prompting mixed reactions from commuters. The campaign claims to reveal 'the hidden truth' behind farmed salmon and pressure supermarkets selling it.
Salmon is the UK's top-selling fish, with sales reaching nearly £1.6 billion. The vast majority of salmon on UK supermarket shelves is Atlantic salmon, farmed predominantly in Scotland, where there are more than 200 salmon farming sites, mostly along the west coast, Shetland, and Orkney.
What the campaign claims
Project Slingshot, a vegan-led group largely funded by American philanthropists, describes Scottish salmon farms as 'overcrowded' and 'filthy' places where 'flesh-eating sea lice are endemic'. Grim campaign posters show fish with missing eyes and chunks of flesh eaten away by parasites.
The campaign also highlights farmed fish being treated with 'toxic chemicals' such as emamectin benzoate, an antiparasitic medicine, and insecticides like azamethiphos, used to control sea lice. In open-net farming, residues from these chemicals can enter the surrounding environment, potentially polluting water and harming marine life such as shrimp and lobsters.
Wild salmon in 'crisis'
Wild Atlantic salmon are endangered in Great Britain, with numbers falling by more than 70 per cent in recent decades. According to the Atlantic Salmon Trust, the fish face a 'crisis' caused by factors including climate change, biodiversity loss, habitat degradation, water pollution, disease, barriers to migration, water abstraction, and open-net pen salmon farms.
Thousands of fish have escaped from farms when nets tear, and the Trust says 'farmed fish interbreeding with wild populations reduces their genetic integrity'. Scientific research shared by the Scottish Government indicates a risk that sea lice from fish farms 'negatively affect populations of salmon on the west coast of Scotland'.
What the regulators say
SEPA (the Scottish Environment Protection Agency) acknowledges that open-net salmon farms can impact the surrounding marine environment. Its website states: 'Waste products like fish excreta, uneaten food, used fish medicines and other chemicals are discharged through the nets into the marine environment.' SEPA regulates these discharges and has set environmental standards for substances such as emamectin benzoate.
Farmed salmon can contain trace residues of veterinary medicines and pesticides, but levels are said to fall well below maximum permitted safety limits set by the UK Food Standards Agency. Food Standards Scotland says sea lice do not pose a public health risk, explaining that the parasite lives only on the outside of the fish and is never found inside the product.
Colour and welfare concerns
Farmed salmon flesh is not naturally as pink as wild salmon due to diet. Wild fish get their vivid pink colour from astaxanthin, a naturally occurring pigment found in organisms like shrimp, krill, and zooplankton. Farmed Atlantic salmon receive this pigment through formulated feed, with synthetic astaxanthin widely used, though it can also be sourced naturally from microalgae, yeast, and certain bacteria.
The Soil Association has announced it is withdrawing from setting standards for organic salmon after an extensive review found issues including high mortality rates, concerns around 'preventing suffering', feed sustainability, and disease. Helen Browning, chief executive of the Soil Association, said: 'When we started working on salmon 20 years ago, we had an aspiration for an aquaculture system that could deliver the principles of organic production in the sea... However, progress along these lines has been negligible.'
Industry and chef responses
A campaign by WildFish called Off The Table has brought together chefs and restaurants pledged to remove farmed salmon from menus, including Michelin-starred chef Angela Hartnett OBE and her Cafe Murano sites, chef Luke Holder, food critic Tom Parker Bowles, Gordon's Wine Bar, and Polpo.
Salmon Scotland, the trade body representing Scotland's salmon farming industry, told Metro that 'Scottish salmon farmers provide the highest welfare standards for the animals in their care, and our sector is highly regulated with full transparency'. It claims Project Slingshot presents a 'distorted picture' of the sector, adding that if campaigners drove Scottish salmon off shelves, demand would be met by imports from countries with lower standards and a bigger carbon footprint.
In 2024, the British government said the Food Standards Agency was 'not aware of any evidence to indicate that fish farmed in the UK are unsafe to eat'. Jim Bligh, Director of Food Policy at the British Retail Consortium, commented: 'Retailers are committed to sourcing seafood responsibly and have their own robust sourcing requirements covering animal welfare and the environmental impact, and these will not change as a result of this decision.'
The NHS recommends eating at least two portions of fish a week, including one oily fish such as salmon, which is high in long-chain omega-3 fatty acids. It advises some groups, including girls, women planning a pregnancy, and pregnant or breastfeeding women, to eat no more than two portions of oily fish a week due to pollutants that may build up in the body.
