We do this via a range of preventative and continual measures, supported by immediate remedial measures when needed.

This ‘prevention over cure’ approach has helped us bring about a real and measurable improvement in fish welfare, contributing to us achieving an average annual survival rate of 83% for the last full farming year (2022), bringing our five-year average to 89%.

But we’re not resting there. In both cases, we’ve set ourselves the target of achieving 95 per cent survival.

Selective breeding

Our work in fish welfare starts long before the freshwater hatchery or marine farm stages; it begins with selecting the salmon traits most likely to thrive in Scottish marine conditions.

We source our eggs from specialist salmon breeders, selecting from over 20 different genetic and biological traits to help maximise resistance to common health challenges, minimise the time required at sea and deliver a higher quality product for customers.

Each batch is fully traceable and documented from egg to harvest, meaning we know exactly where each individual salmon came from.

You can read more about how we can trace our fresh farmed salmon from egg to plate here.

Future-proofing welfare

As part of our commitment to giving our fish the best start, we’re working with Aquagen to breed eggs from salmon grown at our own marine farms; part of a project aimed at improving overall robustness to Scottish marine conditions, increasing resistance to the health challenges that the changing environment can give rise to and future-proofing fish welfare for years to come.

You can read more about this work here.

Scottish Sea Farms Head of Fish Health and Welfare Dr Ralph Bickerdike with AquaGen Scotland MD Andrew Reeve

Fish husbandry

Good husbandry is key to fish welfare and we’re proud to farm to RSPCA welfare standards for farmed Atlantic salmon and the Code of Good Practice for Scottish Finfish Aquaculture.

These set the benchmark for each and every aspect of the farming cycle: from freshwater to seawater to harvest.

This includes:

  • Farming at locations with good quality water with plenty of oxygen to help the salmon grow
  • Stocking our pens in low densities of 1.5% fish to 98.5% water to give salmon plenty of room to swim and shoal
  • Protecting fish from predation by wild birds and seals
  • Prioritising fish welfare in every area of our farming activities; for example, minimal movement of fish and careful handling procedures
  • Investing in specially developed feeds to provide a nutritionally complete diet at each stage of the growing cycle
  • Ensuring that key fish welfare parameters are met via regular routines and record-keeping.

Making sure these standards are being adhered to at all times, RSPCA Assured assessors independently audit each individual hatchery and marine farm, as well as well-boats and our processing facilities.

Sea pens are stocked at low densities of just 1.5% fish to 98.5% water

Preventative and continual measures

Ahead of each new crop, each farm is left fallow – in other words, without fish – for a period of six weeks or more, creating a biosecurity break between crops and giving the seabed an opportunity to replenish itself.

We’ll then equip the farm with a number of preventative and continual measures aimed at giving the new crop of fish the best possible conditions in which to grow:

  • Clean pens and nets – with the nets washed on a weekly basis to prevent fouling by seaweed and other organisms, and ensure good water exchange
  • High-tech feeding systems – installed on feed barges and allowing our farmers to start, stop and adjust portion size to the nearest 50g, according to fish appetite. Many of our farms now have the ability to operate these systems remotely ensuring that our fish can continue to be fed, even if severe weather makes it unsafe for our teams to make it out to the farm
  • Underwater cameras – enabling the team to watch for any changes in behaviour as a welfare check and ensure that fish are feeding well (a key sign of healthy fish)
  • Environmental monitoring equipment – measuring water temperature and oxygen levels in real-time so that any potentially harmful changes in water quality such as a phytoplankton or algal bloom can be quickly identified.
Matching feed portion to fish appetite

Depending on the local marine conditions, our farms might also be equipped with:

  • Sea lice shields – made from a permeable fabric that encases the fish pen to a depth of between 6m-10m, these shields have been specially designed to let water and oxygen in whilst keeping out sea lice which are most commonly found in the first few metres below the water’s surface
  • HDPE netting systems – which combine a tougher surface with tighter tensioning to help protect our salmon from seal attacks
  • Cleaner fish – so-called because, when put into sea pens alongside farmed salmon, they have been found to nibble off or ‘clean’ the salmon of naturally occurring marine parasites such as sea lice which, if left to multiply, can impact on the salmon’s health. We deploy two species of cleaner fish, ballan wrasse and lumpsuckers, and you can read about them in more detail here.

Remedial measures

Sometimes, despite all our best efforts, health challenges develop in some fish and immediate remedial action is needed.

The best course of action will depend on the particular health issue, with the two main challenges being:

Gill health 

The gills are central to the overall health and wellbeing of fish, and the factors affecting them are highly complex. As such, much research is underway across the sector to increase understanding of these vital organs, the key risks to gill health and how to pre-empt and avoid them.

One of the most common gill heath disorders is amoebic gill disease (AGD) which is treated by bathing the fish in freshwater or a solution of seawater and Paramove® (diluted hydrogen peroxide, as is found in every day personal care products such as eye drops, contact lens solutions and mouthwash).

You can read more about this here.

Gill health inspection

Sea lice

Sea lice are naturally occurring parasites that are found in the marine environment and that can attach themselves to a range of wild and farmed fish, their preferred host being salmon.

So whilst all our farmed salmon leave freshwater stage free of lice, they can be affected by them once in sea pens.

There are two main species that affect salmon:

  • Lepeophtheirus salmonis which can be present in the marine environment year round
  • Caligus elongatus which tends to be seasonal and can transfer from migrating wild fish such as mackerel or herring.

Whilst neither species of lice is harmful to humans, they can pose an increasing challenge to the health and growth of salmon if not controlled, particularly Lepeophtheirus salmonis.

Gravid female Lepeophtheirus salmonis. Photo courtesy of Professor James E. Bron, Institute of Aquaculture, University of Stirling

Non-medicinal interventions

In Scotland, if a salmon has two or more adult female Lepeophtheirus salmonis (at reproductive stage) then farmers are required to notify Marine Scotland about what actions are being taken to reduce the level and demonstrate control of this environmental pest.

Previously, this would have been medicinal treatment, either in-feed with the medicine Slice® or via a bath treatment with an authorised veterinary medicine.

Due to the lack of newly developed veterinary medicines for fish however, and as part of our drive to keep the use of veterinary medicines to an absolute minimum, we’ve recently invested in two methods of physical delicing:

  • Thermolicer treatment
    Both chemical and medicine-free, the thermolicer helps reduce lice, just as is done with other farmed livestock. The fish are drawn out of the pen and bathed briefly in lukewarm seawater (water 20°C above ambient seawater to a maximum temperature of 34°C) for less than 30 seconds. This brief change in temperature causes the lice to fall off. The lice are then filtered out and disposed of responsibly, not put back into the sea. You can watch our short animation here.
  • Hydrolicer treatment
    Again, using only water and no medicines, the Hydrolicer uses low pressure water jets to dislodge lice from the salmon. As with the thermolicer, the dislodged lice are filtered out and carefully disposed of, reducing the number of lice in the sea.
The Kallista Helen, with next generation thermolicer, docked at West Burrafirth, Shetland. Photo courtesy of Calum Fraser

Veterinary medicines

As with all livestock farming, veterinary medicines have an important role to play in safeguarding the welfare of our stock.

Where we do use them, they will be authorised veterinary medicines, prescribed by a qualified veterinarian and administered at an appropriate dosage that has been approved by the Scottish Environmental Protection Agency and Veterinary Medicines Directorate.

You can read more about our work to reduce the use of medicines here.

Orkney vets Leona Robertson and Andy Cant of Northvet with Scottish Sea Farms Head of Veterinary Services Ronnie Soutar

Cleaner fish welfare

Our work to enhance fish welfare doesn’t stop at salmon; we have an equal responsibility to look after the cleaner fish in our care too.

In addition to adhering to RSPCA welfare standards for cleaner fish, recent years have seen us:

  • Appoint our own in-house fish health specialists at every farm
  • Introduce special feed to meet the specific nutritional requirements of both lumpsuckers and wrasse
  • Emulate their natural habitats by adding kelp-like hides to sea pens, giving cleaner fish somewhere to rest between periods of activity
  • Develop our own in-house best practice in wrasse and lumpsucker husbandry
  • Co-fund research in farming ballan wrasse and lumpfish welfare to help accelerate our understanding of their needs.

When the salmon are harvested, the cleaner fish will either be relocated to another farm in accordance with the Code of Good Practice for Scottish Finfish Aquaculture, following appropriate biosecurity protocol, so that they can carry on working, or they will be euthanised humanely in accordance with RSPCA welfare standards for farmed Atlantic salmon.

You can read about how we harvest our fish here and what we’re doing to ensure we source cleaner fish in a responsible way here.

Feeding cleaner fish diets tailored to their needs

Specialist fish welfare team

Supporting our farmers in the drive to ensure that fish live the best lives possible while in our care is a dedicated fish welfare team, led by our Head of Fish Health and Welfare and comprising a collective of in-house and external vets, regional fish health managers, cleaner fish specialists and, out on every farm, husbandry staff with specialist fish health training.

When the salmon are market-sized and ready to be transferred from their sea pens onto the well-boat – a process known as harvesting – we have a fish welfare officer present on-farm throughout.

The well-boat’s CCTV cameras record the process, along with the salmon’s journey thereafter as they are transported to our nearest processing facility.

Once there, they are processed by operatives who are fully trained in fish welfare – all of which is also recorded by CCTV – helping ensure the most humane, respectful end of life.