Lice and Chemicals on Fish Farms

All Scottish salmon sold in supermarkets is factory farmed and in those overcrowded, filthy sea pens disease and suffering is rife. One of the most common problems is sea lice infestation. These little parasites cling to the fish and quite literally eat them alive. Investigators have filmed fish with damaged and missing eyes and whole chunks of their flesh eaten away.³

To combat this, farms introduce tens of thousands of lice-eating lump fish to the pens but too often, they cannot survive the conditions any more than the salmon can.⁴ There are “thermolicer” machines, often paid for by taxpayers,⁵ but these can also harm and kill large numbers of fish.⁶ And so the industry relies on some of the most toxic chemicals, including emamectin benzoate (which is poisonous to birds, mammals, fish and other aquatic organisms),⁷ deltamethrin (which is highly toxic to lobsters),⁸ and azamethiphos (also highly toxic with the recommended treatment concentration causing 100% mortality in crustaceans).⁹ The industry also uses formaldehyde (yes, the stuff they embalm dead bodies with) to treat fungal diseases and parasites.¹⁰

These and other chemicals can cause as much suffering to the fish as being eaten alive by lice. In 2024, 60,000 animals died on one day at one farm during chemical treatment for lice.¹¹ These chemicals are also deeply damaging to the environment. By 2017, at least 45 Scottish lochs had been polluted with fish farm chemicals and the industry has continued to use them since.¹²