A SCOTTISH salmon farmer has introduced his stock to underwater ball games and hide-and-seek, to stop the young fish nipping at each other’s fins out of boredom.
Sutherland-based Loch Duart has begun putting brightly-coloured plastic balls in the water for its juvenile fish to play with.
The team started looking for answers as young salmon in the hatcheries have been nipping the fins of other salmon. If left uncontrolled the damage can have a serious long-term effect on the health and quality of the fish.
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Hatchery manager David Roadknight and his team came up with the innovative idea to provide a distraction for the young playful fish.
He said: “This can lead to behavioural problems, with the dominant fish nipping the dorsal fins of their tank mates – a sort of fish tag game with consequences.”
A major cause of biting is interruptions to feeding, either accidental or intentional, which make the salmon hungry and aggressive.
He added: “Other factors such as low water current and higher stocking densities can also contribute, but this could also be linked to other behavioural issues, even boredom.
“When the Loch Duart team started to look at this, we started with both anecdotal and experimental information showing that a consistent and adequate feed supply reduces the amount of fin damage but does not eliminate it.”
As well as the play balls, Duart is putting tarpaulin strips in the water to give the fish a place to hide.
Mr Roadknight said: “Hiding is a natural instinct essential to survival for young fish and now they are able to fulfil this. Hiding also gives a measure of protection against ‘bully’ fish, the major biting culprits.”
Duart has noticed a recent improvement in dorsal fin quality and scientists at Stirling University are now evaluating the new approach.
Jimmy Turnbull, professor of aquatic population health and welfare at Stirling University, said: “This is obviously a very small study and you cannot extrapolate too far from it – but the fish in the tanks with enrichment apparently have better fins and this is very promising.”
Alban Denton, managing director of Loch Duart, said: “Loch Duart is committed to the best welfare achievable.”