Salmon medicated to beat the blues

SALMON may be vulnerable to a bout of the ‘blues’, with symptoms similar to those suffered by humans, a leading Norwegian marine scientist has suggested.

The researcher, Øyvind Øverli, has discovered that some farmed salmon in cages have shown signs of depression familiar in mammals, such as stopping eating or becoming less active.

This can also affect mortality rates, so Øverli injected antidepressants into the fish as part of his experiment. As a result, they became brighter and more active.

The researcher, who is an expert in neurobiology based at the Norwegian Environmental and Biosciences University (NMBU), told the newspaper Dagens Næringsliv that after medication treatment the fish started to eat normally again and displayed renewed energy by moving around more.

He said that prior to the injections their behaviour and psychology was very much the same as that found in mammals suffering from chronic stress.

The researcher has also been studying what happens to the brain’s serotonin system, which can affect behaviour.

He is now trying to find out exactly why salmon are showing these changes in mood. He said if he could find the answer, it may help to bring economic benefits, such as lower mortality.

Ole Folkedal, a fellow researcher at the university, has suggested the stress could be down to inequalities when the fish are very young, or when they reach the adolescence stage.

The university team, which is also looking at the wider reasons behind salmon mortality, plans to continue with its research.