Salmon farms in Norway have suffered from a huge rise of infestations by sea lice, which are becoming increasingly resistant to pesticides. The lice spread to wild fish, weakening and killing them.
Scottish anglers fear that the super lice will spread to Scotland’s fish farms, then deplete the nation’s vulnerable wild stocks. The prospects for wild salmon and trout are “deeply worrying”, they say.
Norway is the world’s biggest producer of farmed Atlantic salmon, producing around 865,000 tonnes a year. Scotland is second, with about 133,000 tonnes a year.
But the Scottish government wants to expand production by about a third - a prospect that is greeted with alarm by the Sea Trout Group. The group was set up by the Scottish Anglers National Association and the Salmon and Trout Association in 1997 to campaign for more controls on fish farming.
“There are strong indications from highly credible sources in Norway of a seriously escalating problem with sea lice control on many of their salmon farms,” said the Sea Trout Group’s chairman, Dr Andy Walker.
“This is due to the development of resistance to the most commonly-used medicines, a very worrying scenario for salmon farming in general that has been forecasted by biologists for some time.”
The Norwegian Institute for Nature Research has estimated that there are over 300 million lice infesting 350 million farmed salmon in cages along the coast of Norway. The industry is six or seven times larger than its environmentally sustainable limit, the institute suggested.
The Norwegian government’s DIrectorate for Nature Management is arguing that salmon farming in Norway must be reduced this year. But its proposals are being strongly resisted by the industry and its supporters in government.
Dr Walker alleged that farms in Shetland had recently been abandoned, partly because of their inability to control lice. And studies by scientists had shown that the resistance of lice to the main pesticide used was growing.
He called for the fish farming industry to introduce “closed containment” technologies to prevent lice from escaping from cages and infesting wild fish. “Otherwise, we are faced with another boom and bust major industry,” he warned, “and a deeply worrying situation for the genetic diversity and abundance of two of our most iconic wild species.”
The Norwegian Salmon Association, an angling group which is campaigning for a boycott of farmed fish, warned that wild fish were facing extinction. “This season, we have experienced catastrophic high levels of sea-lice on farmed salmon in Norway,” said a spokesman for the association.
“The sea-lice have now turned immune to traditional chemical treatment. If the same concentrations are present in the spring when smolts are running the sea, this will kill the whole generation.”
The Scottish government said it was working on a strategy to control sea lice by improving husbandry practices. “This will in turn reduce the need for therapeutants which is the best way to avoid resistance developing,” said a government spokeswoman.
“Last year, the Scottish government signed a Memorandum of Understanding with the Norwegian Government. This is a political statement of intent to safeguard and develop the multimillion pound aquaculture industry through the sharing of research and information.”
John Webster, the technical director of the industry’s Scottish Salmon Producers' Organisation, stressed that circumstances in Norway and Scotland were very different. “Accordingly, appropriate rules are applied to fit the conditions,” he said.