“Large numbers of these lice can be devastating, causing skin lesions, loss of scales, secondary infection and ultimately death.”

An undercover investigation has revealed ‘clear suffering’ at Scottish salmon farms supplying Co-op, Sainsbury’s, Lidl, Aldi, Morrisons, and M&S.

Leading vegan campaigning charity Viva! visited farms in the Highlands to find the fish being kept in ‘putrid’ overcrowded sea pens infested with flesh-eating sea lice.

Scotland is the world’s third-largest producer of farmed salmon, after Norway and Chile.  Brits eat around eight million salmon meals a week.

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Lice infestation

Viva! revealed that around 70 per cent of Scottish salmon farms are RSPCA Assured, while the remainder conform to other supposedly ‘high welfare’ certification schemes such as Best Aquaculture Practices, Marin Trust, GGN Certified Aquaculture and Global G.A.P.

According to the campaigners, whilst adult wild salmon are well adapted to coping with the odd sea louse – a parasite that naturally occurs in the sea – the intensification of salmon farming has led to fundamental changes in the density and occurrence of lice in coastal waters. 

The lice reproduce rampantly, feeding on skin, mucus and blood, which produces white ‘death crowns’ of exposed flesh on the salmon.

“Clearly suffering, the infected fish are regularly seen jumping up to 30 centimetres in the air and skimming along the water surface with their tails in attempts to dislodge the bugs,” the charity team reported.

“Large numbers of these lice can be devastating, causing skin lesions, loss of scales, secondary infection and ultimately death.”

In addition, “huge numbers of juvenile sea lice also escape to the local marine environment, causing significant damage to wild salmon and sea trout smolts, whose fragile skin is not yet adapted to coping with parasites on this level.”

Coping mechanisms

According to Viva!, the aquaculture industry breeds millions of lumpfish ‘cleaners’ to feed on sea lice- a method proven unsuccessful in controlling outbreaks.

Other techniques include chemical washes or mechanical treatments such as hydrolicers and thermolicers, which are likened to a “brutal washing machine”.

Last year, 22 tonnes of formaldehyde was poured into 12 Scottish sea farms in order to kill the lice infestation. This chemical, which has been classified a carcinogen by the government in 2016, is still permitted in the caged salmon industry.

However, the chemical not only causes suffering and stress for the fish, it’s also a major risk to the health of our oceans.

‘Problems similar to factory farms’

Lex Rigby, head of ­investigations, said: “We’re led to believe that aquaculture is the sustainable solution to overfishing, but its rapid intensification has brought with it the same problems we have with factory farms on land.

“The putrid conditions in which farmed fish are reared create a breeding ground for disease that not only causes serious animal welfare issues but also delivers widespread habitat destruction, water pollution and the development of life-threatening drug-resistant ­superbugs.”

• Read: 60% of fish species may succumb to rising ocean temperatures by 2100, study finds

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