A salmon farm that supplies Waitrose and Marks & Spencer has been accused of creating artificially enlarged “Franken-trout” in Scottish lochs.
Activists have accused Cooke Aquaculture, a Canada-based multinational, of allowing fish feed to leak from its salmon cages, leading to the supersized growth of wild trout.
The average Scottish loch trout is well under 1lb, with larger specimens at renowned fisheries getting to 1.5lbs. However, trout near the salmon cages have been reported as growing up to 20lb.
Campaigners say the monster “Franken-trout” is unbalancing the ecosystem, with the large trout eating smaller fish.
Dale Vince, the energy mogul and founder of the Green Britain Foundation, an environmental campaign group, told The Telegraph: “These monster wild trout grow to a size nature never intended. They are Franken-trout gorging on what pours out of the cages.
“You can’t drop a factory farm into a wild loch and pretend you have control of where the feed and the faeces go. Nature is being affected.”
Cooke, which operates fish farms in 16 countries, keeps young salmon in net cages in the north of Scotland and operates a number of fish nurseries across Shetland’s lochs.
Wild brown trout are known to hang around the cages and devour the salmon’s food in a phenomenon known as “cage-grazing”. It is this gorging that is creating the super-sized fish.
Nick Underdown, Scotland director at WildFish, which campaigns to protect fish and their habitat, said: “Artificially fattening wild trout on industrial salmon feed can dramatically distort their natural distribution and role as predators within a loch.”
One of the places where the super-sized trout are most common is the Loch of Cliff, the longest loch in Shetland. A local fishing guide notes: “The loch was once noted for many small brown trout, but since fish cages were installed, the native fish have grown much larger.”
Cooke, which also supplies the likes of M&S and Tesco, operates across Shetland and Orkney, including at the Loch of Cliff. A spokesman said the site was “subject to strict environmental regulations and ongoing monitoring.”
‘Cage-grazing’
As well as salmon feed, the impact of tons of fish faeces from salmon farms leaching out into freshwater lochs is also highly contentious. Scientists have noted that a high concentrations of fish faeces may lead to reduced water quality. This is rejected by the salmon farming industry.
Elsewhere in Scotland, antibiotics are used at salmon farms to limit disease outbreaks. The antibiotics are usually administered through feed and can fall through the cages to be eaten by the “cage-grazing” trout.
A spokesman for Cooke told The Telegraph that they had not used antibiotics at “Loch of Cliff for many years”.
The concerns raised by activists form part of a wider campaign to get the British public to stop eating farmed salmon. Activists and anglers believe that salmon farms are breeding grounds for sea lice, which devour the flesh of passing wild salmon. There are also concerns that escaped farm salmon are weakening the genetics of their wild cousins through interbreeding.
A Scottish government spokesman sought to play down the concerns. They said: “There are a small number of freshwater lochs in Scotland which are used to produce young Atlantic salmon for ongrowing in sea cages.
“Some wild brown trout will forage on uneaten fish farm pellets as they pass through cages and these individuals may attain a larger size than other fish.”
They added: “There is no evidence that localised excess food derived from these sites affects the viability of brown trout populations.”
Waitrose declined to comment.