The angling group, Salmon and Trout Conservation Scotland (S&TCS), has attacked the supermarket chain for continuing to market caged salmon from the north west coast of Scotland that could harm wild fish.
Salmon farms have long had a problem with sea lice, tiny natural parasites that eat fish alive. Lice can multiply in cages holding many thousands of salmon, and then spread to passing wild young salmon and sea trout and kill them.
S&TCS complained a year ago that Sainsbury’s salmon came from fish farms that failed to meet industry guidelines on lice infestation. The group was then assured by company managers that the problem was being dealt with, and lice infestations would end.
But S&TCS says that lice levels on salmon farms at Loch Duich, Loch Alsh and Ardintoul near the Isle of Skye breached the industry’s good practice code in the last three months of 2015. In December average levels reached nearly seven adult female lice per fish, compared to a recommended threshold of one.
The salmon farms are run by the Norwegian seafood multinational, Marine Harvest, and supply fresh salmon fillets and smoked salmon to Sainsbury’s. According to their packaging, they are “responsibly sourced”.
S&TCS director Andrew Graham-Stewart accused Sainsbury's of “paying lip service” to the protection of wild fish. “A year ago, Sainsbury's assured us that their supplier's dismal failures in sea lice control would not be repeated,” he said.
“This assurance has proved to be wanting. If Sainsbury's is serious about tackling this issue, the obvious solution is for it to refuse to accept farmed salmon from those farms that fail to keep sea lice numbers within agreed limits.”
Graham-Stewart pointed out that recent infestations occurred despite the heavy use of anti-lice pesticides. Chemical treatments to kill lice were applied eight times in the last three months of 2015, he said.
He also criticised Sainsbury’s for suggesting that wrasse or lumpsucker fish would increasingly be used to eat the lice off salmon. But inspections by the Scottish Government’s Fish Health Inspectorate at two of the Sainsbury’s farms in July and November last year found none of these “cleaner fish” present.
“West coast salmon farms have long been releasing huge numbers of juvenile sea lice into the surrounding sea loch environments with serious implications for local wild salmon and sea trout populations,” said Graham-Stewart.
“All supermarkets have a huge part to play in protecting wild salmon and sea trout by making it crystal clear to the salmon farmers that they will not buy and then sell on to their customers any farmed fish from those Scottish farms that cannot or will not control their sea-lice numbers.”
Bill Whyte, chairman of the Wester Ross Area Salmon Fishery Board, warned that billions of lice were spread by salmon farms. This was a “scourge on wild salmon and sea trout stocks in the west Highlands,” he said.
“Surely supermarkets have a duty to insist that their suppliers operate without posing a major threat to the wider environment.”
Sainsbury’s stressed that sea lice occurred naturally, and did not pose a threat to human health. Its suppliers were introducing wrasse and lumpsucker fish to tackle lice, it said.
A spokeswoman for the supermarket said: “We remain committed to addressing the concerns raised by S&TCS and working with our supplier continue to make good progress.”
Marine Harvest insisted it was “one hundred per cent” committed to reducing sea lice at its farms. “We are investing more than £6m to increase the numbers of wrasse grown for use in our farms,” said company manager Steve Bracken.
“We have also been very pleased with the development of new technologies which physically remove the sea lice from salmon using increased flow or temperature of the water,” he added.
“We have never suggested this would eradicate sea lice totally overnight - indeed sea lice will always be naturally present in the environment. What we are doing is developing and introducing a range of long term solutions which will take some time.”