Pesticides from 12 salmon farms have contaminated lochs around Scotland’s coast in breach of safety limits, according to the Scottish Environment Protection Agency (Sepa).
Environmental monitoring by the government watchdog over the last three years has discovered high levels of toxic chemicals in sediments from the Firth of Lorn, the Isle of Lewis, the northwest Highlands and Shetland. Fish farmers use the chemicals to kill the lice that eat away at salmon.
By far the worst pollution was found in Loch Shell on the east of Lewis near a fish farm operated by the Norwegian-owned company, Marine Harvest. There, levels of a pesticide called teflubenzuron, were up to 455 times higher than Sepa’s environmental quality standards in 2012.
Sepa is now reviewing the operating licence for the Loch Shell fish farm with a view to imposing restrictions on the volume of pesticides that can be used, and the mass of salmon that can be kept in cages. In 2011 fishermen blamed pollution from the farm for killing off a valuable prawn fishery in the loch.
Marine Harvest said it was “deeply disappointed” by the pollution detected in Loch Shell. The high levels were “very much outside the norm”, according to the company’s business support manager, Steve Bracken.