Food pellets laced with the chemical teflubenzuron have been used to prevent sea lice infestations in farmed salmon. However, salmon excrete the chemical, which then pollutes the seabed around fish farms at levels than can be lethal to some marine wildlife, reports TheHerald.
The latest research on teflubenzuron was conducted by scientists from the Institute of Marine Research and the National Institute of Nutrition and Seafood Research in Bergen, Norway.
They detected high concentrations in sediment around a salmon farm on a fjord north of the city.
They estimated that it took 170 days for the teflubenzuron pollution to reduce by half, suggesting that it will persist in the marine environment for years. The drug was found in most of the wildlife they tested, including worms, crabs and fish.
In a study published in the journal, Science of The Total Environment, the researchers concluded that the levels in king crabs, shrimp and two species of lobster were high enough to kill them as they naturally shed and replace their shells. Teflubenzuron is designed to prevent animals from making chitin, a tough cellulose material vital for renewing shells.
Skretting, which manufacturers the drug said that it "will no longer be offered in Scotland pending further review with all stakeholders."
The Scottish Salmon Producers' Organisation, which represents the fish farm industry, said that teflubenzuron was "not an issue in salmon farming in Scotland today because it is so rarely used".