Below, we answer some of the questions we’re most frequently asked about salmon farming.

Helping ensure that Scottish farmed salmon meets growing demand for food in a responsible, sustainable way, the sector is regulated by not one organisation but several different bodies – each with its own remit. 

In order to gain consent for a new salmon farm, expansion or relocation, we must apply for:

  • Planning permission
    This is done via the local council, with the application being assessed alongside the socio-economic impact – including an Environmental Impact Assessment where required
  • SEPA CAR licence
    The Controlled Activities Regulations (CAR) licence, if awarded, sets limits on fish volume (and, in turn, fish waste) and medicine use in order to minimise the environmental impact from the salmon farm, taking note of the environment’s capacity to disperse materials and any local sensitivities. It also sets out clear monitoring requirements, with SEPA officers carrying out inspections of the farm once operational and publishing the results in their Compliance Assessment Scheme (CAS)
  • Marine licence
    This is obtained from Marine Scotland and covers all navigational aspects associated with farm infrastructure in relation to other marine users
  • Aquaculture business authorisation
    This places a duty on us to operate our farms in compliance with Marine Scotland requirements in a number of key areas including, but not limited to, fish welfare, fish containment, sea lice management and various equipment standards
  • Crown Estate Scotland lease
    Once all these licences have been applied for, we must then apply to Crown Estate Scotland for a seabed lease.

All of which act as checks and balances to help protect both the surrounding environment and other marine users.

Most food producers have an environmental footprint of some kind. In the case of salmon farms, this is known as the benthic impact and refers to the seabed under and around pens where fish faeces and uneaten feed or veterinary medicines can land.

Over time, these deposits can cause a change in habitat. Under the pens this consists mainly of an increase in the abundance of the ‘re-worker’ worm species, with the degree of change decreasing towards the edge of the footprint – the mixing zone. Equally, should farm activity cease, recolonisation and recovery will take place.

SEPA determines what is an acceptable benthic impact based on the particular local water body. In other words, what volume of waste materials (and therefore, what volume of fish) the environment can sustain based on the strength and direction of the current, along with the natural capacity of the animals living on and in the seabed, and other physical processes, to breakdown those materials.

This helps ensure that the footprint of each fish farm is limited both in scale and impact, and that both the habitat and community of animals outwith the mixing zone remain unaffected.

It’s our responsibility as farmers to adhere to the safe levels set and ensure the quantity of waste from our pens doesn’t exceed the seabed’s natural capacity to recycle it.

The volume of waste materials from a salmon farm is carefully matched to the environment’s capacity to disperse and/or absorb those materials. This helps ensure they do not reach levels that would adversely affect the local marine environment or its marine life.

To achieve it, SEPA specifies the maximum tonnage of fish that any one farm can stock at any one time; something that is informed by depositional modelling and Marine Scotland Locational Guidance for benthic impacts and dissolved nutrients. This maximum tonnage is then stipulated within the salmon farm’s Controlled Activities Regulations (CAR) licence.

The healthier the marine environment, the healthier our fish, so it’s within every farmer’s best interests to adhere to the limits set. We’ve also invested in camera-monitored feeding systems that enable us to monitor when the fish are hungry and when they are not, helping ensure that as little feed is wasted as possible.

As with human health and other farmed animals, medicines are sometimes the best option for the control and prevention of disease and parasites amongst farmed fish. 

Likewise, as with human medicines, veterinary medicines must be approved and shown to be safe and effective for use – not just in terms of the animal itself, but in terms of public health and the environment.

Any veterinary medicine used on our farms is prescribed by a registered veterinarian based on the assessment of the needs of the fish under their care and any medicinal treatments are administered in accordance with SEPA licensed limits.

Veterinary medicines and their uses
The majority of veterinary medicines that we use are for the prevention or removal of sea lice:

  • Salmosan®Vet and Azasure
    Both medicines contain the active ingredient azamethiphos which is a biodegradable water-soluble organophosphorus compound that remains in the water column until it is broken down. Organophosphorus compounds have been and are still used extensively in fruit and vegetable production, in sheep dips and are a major component in non-prescription flea collars widely used by UK pet owners.

    In salmon, these medicines are administered as a bath treatment. Bath treatments are undertaken in reduced volumes of water using a tarpaulin enclosure and once the treatment is complete the water containing medicine residues is released. The residues are rapidly diluted as they are dispersed into the surrounding water where they are broken down into non-toxic transformation products.

  • AMX
    The medicine AMX contains the active ingredient deltamethrin; a pyrethroid or organic compound used for controlling insect pests in agriculture, public health, and animal health.

    AMX is administered as a bath treatment. Once the treatment is complete, the water containing medicine residues is released. As the ingredient deltamethrin is not water soluble, it quickly sinks from the water column to the seabed where it is broken down.

  • SLICE®
    SLICE® is a veterinary medicine that contains the active ingredient emamectin benzoate and is administered as an in-feed treatment at a level below the fish’s normal appetite to minimise the risk of medicated food being uneaten.

    Emamectin benzoate has low water solubility and the small amount present in fish faeces and binds to sediment particles until it is broken down.

  • Paramove®
    Paramove® contains the active ingredient hydrogen peroxide which is common to many human, domestic and cosmetic products. It is administered as a dilute bath treatment at or below 0.15% concentration hydrogen peroxide – that’s a 10th of the strength used in a typical mouthwash – and rapidly breaks down into just water and oxygen.

    SEPA considers that, when used in accordance with its product and CAR licence, it presents next to no environmental risk, therefore no numeric limits are imposed on its use.

Farmed salmon are routinely examined for overall health, including the presence of any parasites. To ensure their well-being throughout this process, our fish are anaesthetised before handling. This involves the use of small quantities of anaesthetics which, like the lice treatments, are licensed medicines used under prescription.

To ensure we would be able to respond to any infectious disease, we also have licenced permission to use specific antibiotics if necessary. However, Scottish Sea Farms has a long-standing policy of limiting antibiotic use through best practice farming methods, with the result that we have not used any antibiotics at any of our marine farms since 2012.

Each and every licensed medicine, whether for human or animal health, has a known safe and precautionary quantity for public and environmental health.

Any veterinary medicine administered on our farms is used strictly in accordance not just with its product licence but our SEPA CAR licence too.

The role of SEPA
SEPA regulates the discharge of all priority listed substances (substances with the potential to result in harmful environmental effects, if not used in the specified safe amounts). It does this by defining Environmental Quality Standards for each priority listed substance and setting concentration levels to protect the surrounding marine environment (sensitive species).

Each farm is given its own CAR licence which sets precautionary limits on the levels of medicinal residues that may be released to ensure that the Environmental Quality Standards are not exceeded and that medicine use does not result in harm to the wider environment.

Further protecting human health
Also protecting human health, organisations such as the European Union, the World Health Organization and the Food and Agriculture Organization determine:

  • Acceptable Daily Intake (ADI) – the estimate of the residue, expressed in terms of micrograms or milligrams per kilogram of bodyweight, that can be ingested daily over a lifetime without any appreciable health risk
  • Maximum Residue Limit (MRL) – the maximum concentration of residue resulting from the use of a veterinary medicinal product (expressed in mg/kg or ug/kg on a fresh weight basis) which may be accepted by the EU to be legally permitted or recognised as acceptable in or on a food.

In-feed medicines
SLICE® contains the active ingredient emamectin benzoate and is administered as an in-feed treatment. Emamectin benzoate has low water solubility and binds to sediment particles until it is broken down, and therefore does not pose any risk to water users.

Bath medicines
Medicinal bath treatments are administered in a reduced volume of a salmon pen using a special tarpaulin and the treatment water contains very low concentrations of the active ingredient of these medicines. When residues are later released at the end of a treatment they are immediately dispersed and diluted to significantly lower concentrations which are not considered a risk to human health.

  • Paramove® contains the active ingredient hydrogen peroxide in a 50% solution and is used as a bath treatment at a concentration of 0.15% or less. Given that hydrogen peroxide rapidly breaks down into the non-toxic products of oxygen and water the use of this medicine is not a risk to water users in the vicinity of a farm.

    Similarly, SEPA considers that its safe use at salmon farms presents a minimal environmental risk and therefore does not impose numeric limits on the use of the medicine.

  • Salmosan®Vet and Azasure are both medicines which contain the active ingredient azamethiphos which is a biodegradable water-soluble organophosphorus compound. Reduced volume bath treatments are undertaken at a concentration of 0.1 parts per million (0.1mg/kg). Once the treatment water is released from the salmon pen the medicinal residues are immediately dispersed and diluted to significantly lower concentrations which are not considered a human health risk in terms of ingestion or skin contact.

    The quantities of pen treatment water that would need to be ingested to result in an intake higher than the Acceptable Daily Intake (ADI) for azamethiphos, and result in any risk to human health, would be more water than a human could physically drink in a day and the greatest risk in terms of toxicity would be the level of salt in the sea water.

  • AMX contains the active ingredient deltamethrin which is not water soluble. Bath treatments are undertaken in reduced volumes of water using a tarpaulin enclosure and once the treatment is complete the water containing medicine residues is released. Reduced volume bath treatments are undertaken at a concentration of 2 parts per billion (0.002mg/kg); once the treatment water is released from the salmon pen, the medicinal residues are diluted to even lower concentrations.

As farmers, the last thing we want to see is another animal come to harm. Equally, we have a responsibility to protect the fish in our care – including from predation by seals. 

Often, the two co-exist with little problem; a situation helped significantly by ongoing development of, and investment in, new netting systems. These systems however, whilst a huge advance in the drive to keep seals and salmon safely separate, are not yet 100% failsafe, meaning attacks still occur.

Previously, fish farmers were permitted under licence from Marine Scotland to shoot a predatory seal where it had persisted beyond all other preventative measures.

These same licences limited the number of seals that could be shot to a level below what’s known as the scientific ‘potential biological removal’ limit set by the Sea Mammal Research Unit to ensure there would be no decline in the seal population.

Across the Scottish salmon farming sector as a whole – some 200+ farms – an average of 57 seals were shot under licence between 2015-2019. In comparison, over the same period, the Scottish seal population is reported to have increased by 28% for grey seals and 6% for common seals, with the total seal population now thought to be at least 132,000.

New legislation
As of February 2021, salmon farmers are no longer permitted to kill seals for any reason; a measure that was only ever adopted as a last resort to protect farmed fish.

We still have a clear duty to protect the fish in our care from predation. To this end, our Dunstaffnage, Lismore West, Shuna, Bring Head and Toyness farms will continue to use strong polyethylene netting systems, complete with sinker tubes to maximise net tension and further minimise seal predation.

We do not propose to use acoustic deterrents at any of these farms.

There is a recognition that salmon farms may pose a potential hazard to wild salmonids migrating past salmon farms. The relationship between the two, however is a highly complex one with many potential contributory factors.

Wild salmonid populations are declining and under threat globally including in areas where salmon farms are not present, and many populations were in decline since the mid-1960s, before the salmon farming sector really became established.

Wild salmonids face a wide range of pressures in both the freshwater and marine stages of their life cycle, with climate change highlighted as a significant pressure affecting survival and growth at sea. Any effects from fish farming could add existing pressures on wild stocks, however there is still considerable uncertainty, and despite many studies none have shown a conclusive link between salmon farming and the continued decline in wild fish numbers in Scotland.

To help address the uncertainties, the current regulatory framework requires applications for any new or extended salmon farms to implement an Environmental Management Plan (EMP); a detailed and robust template for which has been developed and agreed in consultation with Salmon Fisheries Management Scotland and the local Salmon Fisheries Boards and Trusts.

This EMP provides a defined reporting and review process to enable an ongoing ‘adaptive management’ approach where farm management measures can be reviewed and amended in response to ongoing farm and wild fish monitoring. This means that if monitoring suggest impacts on wild salmonids as a result of farm operations, particularly sea lice numbers, appropriate changes to farm management measures can be agreed through the adaptive management process.

Sea lice are tiny parasites that occur naturally in the marine environment (including locations where there are no fish farms, such as Scotland’s east coast) and latch onto both wild and farmed salmon.

So whilst our young salmon arrive at sea from our freshwater hatcheries free of lice, it’s our responsibility to monitor and control lice levels thereafter.

We do this in a number of ways depending on farm location: from physical barriers such as lice shields that wrap around pen netting, to the proactive removal of lice via ‘cleaner fish’ (so-called because they co-exist alongside salmon, nibbling off any lice) and water-based delousing treatments that help remove the lice from the marine environment.

Sometimes, the best option in the long-term interests of fish welfare is a medicinal sea lice treatment; something we would administer either via a bath treatment or within fish feed. You can read more about the medicines used in the control of sea lice by scrolling to the earlier question, ‘How often are medicines used and in what amounts?’

The combined result of this proactive approach is that we’ve achieved a steady reduction in sea lice levels across our farming estate over the last five years.

Good husbandry is key to fish health and welfare and we’re proud to farm to RSPCA Assured welfare standards for farmed Atlantic salmon.

These set the benchmark for each and every aspect of the farming lifecycle – from freshwater hatcheries to marine farms to harvesting – with farms and facilities independently audited.

In 2020, this commitment to best practice in each and every area saw us achieve an average farmed fish survival rate of 92% (compared to an estimated survival of 5% or less in the wild), bringing our five-year average to 91% – and we’re not stopping there.

We always working, always investing, to pre-empt and prevent the challenges presented by the marine environment in order to boost fish welfare and survival rates even further.