300-kilo ‘invader’ hits Hebridean salmon farm

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Workers on a Marine Harvest Scotland site off the Hebridean island of Colonsay could hardly believe their eyes when a three-meter-long Pacific Blue Fin Tuna appeared in one of their pens.

Since the farm opened in August 2015, the team have become used to seeing a lot of marine wildlife, but as Farm Manager Ali Geddes explained, this was unusual: “We’d noticed a lot of activity around the southern part of the farm – there seemed to be a real feeding frenzy going on with the dolphins and porpoises. It’s now clear they were chasing a tuna. These things can move at real speed – up to 50 mph – and it seems to have burst through the foot of the pen like a torpedo.

“Thankfully the tuna seems to be unhurt and none of our own fish have escaped. They are very small at this stage – the site has only recently been stocked with smolts which tend to swim towards the top of the pens away from the base. The hole the tuna made was more like a slash than a round hole and we called in divers who repaired it within a few hours.”

Atlantic Blue Fin Tuna are common in Scottish waters, but Pacific Blue Fin Tuna are incredibly rare as they prefer the warmer waters of the North and South Pacific oceans.

The Colonsay team finally used a panel net to capture the tuna. This type of net is normally used during harvesting as it allows smaller fish to swim through the gaps. The landing craft crane was then used to lift the tuna into a large basket for transfer to the open sea where it happily swam away.

Ben Hadfield, Managing Director of Marine Harvest Scotland was delighted the team at Colonsay managed to release the tuna unscathed. “Congratulations to the team for sorting this. It could have been a very different story and it’s testament to their skills that this beautiful fish is still alive and well.”

“They’re skilled in handling fish but our salmon grow to about 5 kilos in size, so this was well beyond the norm. We believe it was a whacking 300 kilos, which is more than 47 stone.”

Marine Harvest’s salmon farm at Colonsay has 12 pens, each 120m in diameter. Ten people are employed at the farm, including the manager.