Scottish salmon sold by supermarkets infested by sea lice

Leading supermarkets have been called on to stop selling salmon reared by Scottish farms, where sea lice infestations are up to 20 times the recommended levels.

Co-op, Tesco and Sainsbury’s all stock salmon from the worst affected farms, as revealed in new data obtained by the Salmon and Trout Conservation Scotland (S&TCS).

Salmon farms are expected to keep numbers of the parasite – which can cause loss of fins, scarring, secondary infections and death – to no more than one louse per farmed fish.

Leading supermarkets have been called on to ban salmon reared by Scottish farms, where sea lice infestations have been revealed as up to 23 times the recommended levels (file picture)

Data obtained by S&TCS lists the farms that reported an average of at least three lice per farmed fish.

Co-op supplier, The Scottish Salmon Company, recorded lice numbers that exceeded acceptable levels at six of its 10 farms, for 52 weeks.

At the firm’s Furnace Quarry farm, each fish was found to have 23 sea lice for a period of seven weeks.

Meanwhile fish at Score Holm farm, run by Tesco salmon supplier Grieg Seafood Shetland, were found to have an average of 22 adult female lice.

Marine Harvest, which supplies Sainsbury’s, was also named on the list. 

Fish infested with sea lice are discarded or treated with pesticides and pose no health risk to consumers.

S&TCS had asked the Scottish government repeatedly since last year to make public the farms that had breached recommended sea lice levels, before the Scottish Information Commissioner agreed to their request last month.


The tiny parasite can cause loss of fins, scarring, infectionc and ultimately death

The tiny parasite can cause loss of fins, scarring, infectionc and ultimately death

Sea lice belong to a group of tiny crustacenas called copepods, and have colonized almost every aquatic habitat on Earth. 

Its like cycle is a series of molts – at the ‘napulii’ stage the sea louse is free swimming, relying on its own internal yolk reserves. 

But at its intermediate copepod stage, the lice use their hooked atennas and frontal filaments to arrach themselves to fish; they are still too small to cause any real damage as they feed on the young salmon.

As the lice near the adult stage, they attach to the fish by suction and can become lethal. 

They’re able to move on the host fish’s body, targetting the head, back and perianal areas – preferring to feed on mucusm blood and skin. 

There are two species found on salmon, Caligus elongates and Lepeophtheirus salmonis. 

The former affects many types of fish, while the latter is found only on salmon and related fish. 

Source: Alaska Department of Fish and Game  

Guy Linley-Adams, Solicitor for S&TC Scotland, said: ‘We now call upon Scottish Ministers to rethink radically their approach to the salmon farming industry, to end the knee-jerk support of the industry in the face of frankly awful environmental performance, and to stop trying to protect it from legitimate criticism.

‘We have shared our ideas for change with Marine Scotland and hope Scottish Ministers will now work with environmental and conservation bodies to map out a sustainable future for the industry that no longer damages the precious Scottish marine environment and the species within it.

‘We also call upon the industry itself to end both its tobacco-industry style denials about the damage it causes and the “tit for tat” accusations it repeatedly makes, in favour of embracing the positive change that must now come’.

He added: ‘The data that Scottish Government didn’t want anyone to see shows that salmon farms have been permitted to operate with breathtakingly high lice numbers for weeks or months on end. 

‘To date, no meaningful enforcement action, such as the ordering of culls or immediate reductions in fish-farm biomass, has been taken against serial offenders.

‘The Scottish Government has a legal duty to protect and conserve wild salmon and sea trout, but this data shows it is failing to rein in the biggest threat [them].”

A Scottish government spokesman said it would work alongside the aquaculture industry to tackle ‘major problems’ including disease and sea lice.

Scotland is not the only affected region, as parasitic sea lice are disrupting salmon farms around the world. 

The lice are actually tiny crustaceans that have infested salmon farms in the US, Canada, Scotland, Norway and Chile, major suppliers of the high-protein, heart-healthy fish. 

Experts say defeating the lice will take a suite of new and established technology, including older management tools such as pesticides and newer strategies such as breeding for genetic resistance. 

The innovative solutions in use or development include bathing the salmon in warm water to remove lice and zapping the lice with underwater lasers.

Farmers worldwide consider sea lice the biggest threat to their industry and say the persistent problem is making the fish more expensive to consumers. 

The lice can grow to about the size of a pea and lay thousands of eggs in their brief lifetime.

Atlantic salmon have held their own with sea lice in the wild for centuries, and fish farmers managed them in aquaculture environments for many years.

The price of salmon has rocketed as sea lice has become a problem for farms around the world

The price of salmon has rocketed as sea lice has become a problem for farms around the world

Farmers in Canada identified the lice as a problem around 1994, said Jonathan Carr, executive director of research and environment with the Atlantic Salmon Federation.

Feeding fish a pesticide with the active ingredient of emamectin benzoate became the tool of choice to control lice.

But around 2009, the lice appeared to become resistant to the pesticide, and they have spread globally since.

The worldwide supply of salmon fell almost 10 percent last year, with Norway, the largest producer in the world, especially hard hit.

The worldwide supply of salmon fell almost 10% last year, with Norway especially hard hit

The worldwide supply of salmon fell almost 10% last year, with Norway especially hard hit