Survival rates returned to historically high levels, up to 90% from 82% in 2023, as the warmer seawater temperatures that had brought sector-wide challenges for two years gave way to better biological conditions. The past 12 months also marked a big increase in harvesting volumes.

“We’re back to where we should be but we’re not complacent,” said head of Fish Health Ralph Bickerdike. “We certainly learned from the challenges of 2022-2023 and have reviewed all our operations, but we want to see even higher survival.”

Broodstock program

Key to improved performance is the company’s breeding program which, in collaboration with AquaGen Scotland, has produced broodstock from Scottish Sea Farms salmon selected for their robustness in the Scottish farming environment.

“It takes three years to get fish up to broodstock size and the first crops from these fish, harvested in 2024, did really well. Every year, we are selecting fish from our farms which will then be used for broodstock. Hopefully, by doing this over successive generations, we will see even more improvement in the climate resilience of our fish.”

Reviews for fish welfare

Feeding was reviewed and diets were altered to help meet the seasonal nutritional requirements for fish health and welfare. “We worked with our feed supplier to adapt the composition of the feed in Q3 when fish health is most likely to be compromised, and the early results are very encouraging.”

Temporary feed withdrawal during times of challenge further contributed to survival, by keeping fish away from the surface when harmful jellyfish and plankton were in the water.

Technological advances

Technological advances in the supply chain also continued to aid fish health across the Scottish Sea Farms estate, enabling earlier detection of disease and quicker interventions, added Bickerdike.

“We’ve been evaluating the latest underwater biomass cameras, which monitor individual fish for weight estimation and assess the condition of the fish without us having to handle them. They can give us real-time indications of welfare parameters, such as skin wounds or sores, which we can then investigate and act on if necessary.”

The use of modern diagnostics, such as PCR swabs for amoebic gill disease (AGD), has led to better-informed treatment decisions, as have daily water sampling and surveillance, which provide a timely record of environmental changes.

All regions have also benefited from new biosecurity checks, pioneered by the team in Shetland, which have minimized the introduction of potential disease with an air table-based app that logs the inspection of vessels or equipment.

Ongoing investment

Also making a difference are the two well boats Scottish Sea Farms secured last year, both fitted with reverse osmosis for freshwater treatments and FLS delousing systems, allowing fish to be treated for AGD and sea lice at the same time, reducing the need for fish handling.

Mainland Regional Production Manager Innes Weir said that the company has been “upgrading farms with fewer but bigger pens – by April this year every farm in mainland Scotland will have moved to larger pens, with an average size of 120m. Going from 12 pens in a mooring grid to five creates a different hydrological dynamic around the farm that seems to promote growth and performance.”

Looking forward

Going forward, Scottish Sea Farms is increasing secondary predator netting for farms that have a higher risk of interaction with seals; further evaluating cleaner fish deployment; upgrading freshwater facilities; and collaborating in a new raft of R&D projects to help understand fish health issues.

“Not only did we come through last year with better survival but we came through it with zero antibiotic use in our production farms,” said Bickerdike. “We have become better at sharing best practices, with the health people, area managers and farm managers from all regions meeting weekly. It’s an important gathering of information that allows us to look ahead. It doesn’t mean something won’t come out of the left field, but we’re in a very much better place to meet challenges now.”