Larger, fewer pens yield major success. The first Scottish Sea Farms site to transition to 160m pens has reported a record harvest tonnage, with an average fish weight of 6.8kg. This move also led to improvements in fish welfare and a reduction in seal predation.
At Fishnish A, located off Mull, ten 100m pens were replaced with four 160m pens. In addition to the larger pens and stronger moorings, the farm introduced Midgard HDPE knotted nets, a new winch system, and trialled a smart feeding strategy, totalling an investment of around £3 million.
Farm Manager Alastair Fraser commented:
“It was like night and day compared to the previous set-up—so much simpler, less labour-intensive, and with far less manual handling. The new winch system is revolutionary; once we got used to it, there was no going back.”
Each walkway now has ten winches, which are operated remotely from a dedicated workboat, offering improved net control and enhancing staff safety.
“Managing three pens instead of ten (we kept one spare for handling or freshwater treatments) allowed us to stay focused on the task at hand and carry out treatments much more quickly.”
The combined tonnage for Fishnish A and B, where half the stock was moved after six months, reached just over 4,000 tonnes. This was an impressive achievement, especially given the challenges posed by mg, which affected the sector between 2022 and 2023.
Fraser credits the success not only to the larger pens but also to the improved husbandry, which offers a lower stocking density, better water flow, and increased oxygen levels. The new feeding system, utilising motorised smart spreaders, delivered “fantastic results” by ensuring all the fish were fed simultaneously and finishing feeding by 9:30 AM so that the fish could dive to the deeper parts of the pens.
With the summer harvest completed, the team is now preparing for the next cycle, planning to implement similar infrastructure at nearby Fishnish B. While they’ll make some adjustments—such as increasing the number of wrasse in the pens to combat sea lice more effectively—they are confident the new infrastructure has been a success.
“The team realised it was a challenging crop, but they could see the benefits of this new farming approach, and morale has definitely improved.”