Escaped farmed salmon threatening wild stocks
Increasing numbers of farmed salmon escaping into Norway's open waters are putting wild species under greater risk of disease, breeding difficulties and genetic contamination, the WWF has warned.
With fish tightly crammed into cages in the open water, fish farms are an ideal breeding ground for disease and parasites such as sealice. Escaped salmon can then take these diseases into the wild with them, infecting the wild, non-farmed population.
Around half a million farmed fish escape into Norwegian waters every year, meaning one out of every four salmon or trout found in Norway's coastal waters are fish farm escapees.
"It's totally unacceptable that such enormous amounts of farmed fish have escaped from fish farms into open waters, undermining the long-term survival of wild salmon," said Maren Esmark, marine coordinator at WWF Norway.
Worryingly, the report also shows that the up-river migration of escaped farmed salmon late in the spawning season physically displaces the eggs of the already spawned wild salmon, considerably reducing the wild species' reproduction ability.
Moreover, the rise in escapees has led to an increase in interbreeding between the two varieties, diluting the gene pool and potentially threatening the survival rate of offspring.
With 500,000 tonnes of farmed salmon and trout produced each year, the fish farming business is a cornerstone of Norway's economy, but WWF warns that Norwegian waters are home to half of the world's Atlantic wild salmon stock, and more should be done to protect them.
"One third of Norway's wild salmon stocks are already suffering because of human activity," director of WWF's global marine programme, Dr Simon Cripps warned. "Add to that the increasing threat of escaped fish and we have to ensure that industry and government clean up their act and begin to act responsibly."
He added that salmon were not the only farmed fish species escaping and putting their wild counterparts at risk, with a considerable increase in escaped farmed cod mixing with already imperilled wild cod also being observed in Norway.
Although the Norwegian government and the country's fish farming industry have already taken some steps to reduce the amount of escaped fish, Dr Cripps urged that more needed to be done.
New measures suggested by WWF included increasing security to prevent fish from escaping, individually tagging farmed fish, and locating fish farms away from vulnerable stocks of wild fish species.
But the report warned that if nothing was done soon, escaped farmed fish would end up damaging Norway's economy as well as the environment.
By Jane Kettle