This is from Friday’s i paper:
Salmon that grow up on a farm are much harder of hearing than those reared in the wild, with half of them suffering a considerable degree of dearness, research suggests.
The hearing loss is caused by a deformity of the earbone which reduces hearing sensitivity by up to 50% – and it is 10 times as prevalent in salmon in aquaculture than in the natural world, says a study published in the journal Scientific Reports. Hearing is crucial not just for its own sake but because the salmon are thought to rely on it heavily for navigation. While the hearing loss is problematic for all afflicted farmed salmon, it has even greater implications for those fish that re later released into the wild for conservation purposes because it makes them far less able to find food and avoid predators.
The fish are not thought to be born with deformed earbones but rather to develop them over time. “This is a very surprising result. We don’t know whether it is down to nutritional deficiency, a genetic problem, or maybe something to do with the rapid growth rate of fish on farms, but it is serious,” said Tomey Reimer, of Melbourne University. “Hearing loss could also seriously be hampering salmon conservation”, she added. Salmon populations are in a serious decline across the world as a result of damming and deforestation.