Salmon farms in the north-west of Scotland are hailing a move to “natural” methods to battle one of the biggest problems facing the industry.
Operators have been using locally caught wrasse as cleaners to remove potentially deadly sea lice parasites from the farmed fish.
The cleaner fish eat the sea lice, which can cling on to farmed salmon while they are being reared.
One operator said the move had been so successful that all medicinal treatments previously used to battle the parasites had been stopped. Gilpin Bradley, managing director of Wester Ross Fisheries, said: “This is the single biggest advance that has ever been made in salmon farming – finding that cleaner fish work.”
The firm uses ballan wrasse caught in the waters around Loch Broom, near Ullapool, to clean its salmon. Lumpfish can also be used.
The wrasse are captured in creels – the company is limited to 250 creels to make sure it does not overfish the area – and put into the salmon pens at a ratio of about one for every 100 salmon.
“We are genuinely maintaining a sustainable level of catches,” Bradley said. “We are only taking medium-sized wrasse, small ones are returned. Big ones are put back because that’s the breeding stock, that’s important.
“Cleaner fish are the gold standard because they are completely all natural.”
Farmed Atlantic salmon is worth more than £1.8 billion to the Scottish economy.
Production rose to a record high of 189,707 tonnes last year – an increase of 16.5 per cent in 12 months – but the industry has been struggling to control pests and diseases.
Environmental campaigners have long railed against the use of chemical pesticides, the most common of which is emamectin benzoate contained in the anti-lice product Slice.
Recent research by the Scottish Environmental Protection Agency (Sepa) revealed traces of the chemical were “more widely spread in the environment around fish farms than had previously been found”.
Emamectin was found in 98 per cent of samples taken around eight fish farms in Shetland.
Another lethal sea lice pesticide, teflubenzuron, was detected in 46 per cent of the samples, despite the fact it hasn’t been used since 2013.
The regulator found “Scottish salmon farm medicine is significantly impacting local marine environments” and is proposing new tightened regulations.
David Harley, head of water and planning at the Scottish Environmental Protection Agency, said welcomed the use of cleaner fish, saying: He said: “Our Finfish Aquaculture Sector Plan is ambitious in its aspirations for an industry where in the future the sector is a world-leading innovator of ways to minimise the environmental footprint of food production and supply.“We support the industry using alternative methods, which reduce the amount of medicine being discharged into the environment.”
David Harley, head of water and planning at the Scottish Environmental Protection Agency, said: “We support the industry using alternative methods, which reduce the amount of medicine being discharged into the environment.”
Loch Duart salmon company, based in Scourie in Sutherland, has also made progress against sea lice using cleaner fish.
Lewis Bennett, cleaner fish manager for the firm, said the move had been a “game-changer”.
However, some campaigners say the aquaculture sector needs to make much bigger efforts to stop harming the environment and improve standards.
“Scottish salmon farming is a dirty rotten industry,” said Don Staniford, director of Scottish Salmon Watch.
“Farms are so filthy that so-called cleaner fish are being eaten alive by lice.”