Fish farms fear after half of their salmon are born deaf

FARMED salmon suffer from deafness because their ears become deformed when their growth is accelerated, research reveals.

Around half of all salmon from farms are at least partially deaf – raising questions about the welfare of the stocks.

Scientists from the University of Melbourne found rapid growth causes tiny crystals, called otoliths, to form in the inner ears.

The deformity was first noted in the 1960s, but this research is the first to show that it affects more than 95 per cent of adult, hatchery-produced fish globally.

Farmed salmon can grow twice as fast as wild fish because they eat food pellets rich in energy.

‘Raises questions about welfare’

Dr Tormey Reimer, from the university’s School of Biosciences, said: ‘We looked at over 1,000 otoliths from fish farmed in Norway, Chile, Scotland, Canada and Australia, and found this deformity was extremely common, but only in farmed fish.

‘The fastest-growing fish were three times more likely to be afflicted than the slowest.’

Study co-author Dr Tim Dempster said: ‘These results raise serious questions about the welfare of farmed fish.

‘Farming practices must allow for the “five freedoms”... Producing animals with deformities violates two of these: freedom from disease and freedom to express normal behaviour.

‘But fish farms are very noisy environments, so some hearing loss may reduce stress in hatcheries and sea cages. We still don’t know what this level of hearing loss means for production.’