"Salmon farmers have been accused of playing dirty by using fish caught in the wild to clean lice from Scottish fish farms. Marine conservation experts say that shipping tonnes of English-caught wrasse a year – to tackle lice infestations in salmon pens north of the border – is endangering natural stocks. English anglers have also warned wrasse is becoming harder and harder to find in local waters.
However, salmon farmers have rejected the charge. They say the use of wrasse as a “cleaner” fish is part of a long-term plan to replace chemicals – which are currently administered to pens to control lice infestations – with sustainable, biological controls.
Salmon farming in crisis: 'We are seeing a chemical arms race in the seas'
Fishermen remain concerned, nevertheless. “Wrasse play a role in keeping the marine ecosystem in balance,” said David Mitchell, of the Angling Trust. “We simply do not know what will be the consequence of removing so many of them from our coastal waters.”"