Scottish Sea Farms (SSF)'s first site to make a switch to 160-meter pens has reported record tonnage at an average salmon harvest weight of 6.8 kilograms, along with improved fish welfare and reduced seal predation, it said.

Its Fishnish A site off Mull saw 10 100m pens replaced with four 160m pens. As well as the bigger pens and heavier moorings, Fishnish also introduced Midgard HDPE knotted nets and a new winch system, and trialed a smart feeding regime, in an investment of around £3 million ($3.8m).

"It was night and day compared to the previous set-up: so simple, less labor intensive, with less manual handling," said farm manager Alastair Fraser said: "The new winch system is another world and once we got the hang of it there was no going back."

read also

Mowi exec urges gov’t help as Scottish salmon farmers bid to cope with climate change

Dealing with three instead of 10 pens (one is kept spare for handling or freshwater treating) allowed managers to stay focused on the task at hand and carry out any treatments much faster, he added.

The combined tonnage for Fishnish A and B, where half the crop was moved after six months, was just over 4,000 metric tons, said Fraser, "quite an achievement given challenges which included the micro jellyfish" that affected most of the sector between 2022 and 2023."

The results were attributed to good husbandry, as well as to the bigger pens, which provided lower stocking density and better water flow and oxygen. The new feeding system, involving motorised smart spreaders produced "fantastic results," ensuring the whole population was fed at the same time, with feeding finished by 9.30 am so the fish could go down to the depths of the pen.

With the fish harvested over the summer, the team is now preparing for the next cycle and hoping to roll out similar infrastructure at neighboring Fishnish B, said SSF.

"While they will do some things differently, such as increasing the ratio of wrasse in the pens to better handle sea lice off Mull, they are convinced the new infrastructure has paid off."

Anne Anderson, head of sustainability and development at Scottish Sea Farms, told a Scottish parliamentary hearing on Dec. 4 that the company had plans to move more of its sites to larger, consolidated setups, but that gaining approvals was cripplingly slow.

"But it's not that complicated to overcome, it's about investing the time to understand. Issues in the sea mean we have to move -- physically move the farm and move our heads around the issues. We need to do it right now, and it needs to occur among regulators and parliamentarians."

Scottish aquaculture businesses "cannot move a farm quickly," she said, "and I want to move a lot of our farms to different locations, and to consolidate, and we have a plan to do that... But for the sector's longevity, you need the ability to move fast."

"I think salmon pen infrastructure is a real critical one, like roads or rail networks -- what would it look like to think of it that way? Would we have faster movement?"