In this section you find answers to questions you might have about salmon farming. If you have further questions, please do not hesitate to contact the head office.

  • Are medicines/antibiotics used in salmon farming?

  • Are farm-raised salmon coloured artificially?

  • How does Mowi control predators taking its fish?

  • How are salmon farms working to control sea lice?

  • Do salmon escape from farms?

  • What emergency measures are you putting in place to ensure your fish do not escape?

  • What impact would a release of your fish into the local waters have?

  • How much stock have you lost over the years from your other locations?

  • Is fish farming causing algal blooms and shellfish poisoning?

  • Are salmon kept in crowded conditions?

  • What is your environmental record?

  • How safe is farm-raised salmon?

  • What do you feed your farm-raised fish?

  • Who regulates the fish farming sector in Ireland?

  • Are sea lice from your farms killing wild fish?

Are medicines/anitbiotics used in salmon farming?

As with humans and other animals, both wild and farmed fish are susceptible to infectious pathogens. If left untreated, diseases (viral, bacterial and parasitic) can compromise welfare and cause significant mortalities in a short period of time, so safe and effective control is vital.

In comparison with the number of medicines available and used in terrestrial (land) food animal production, only a limited number of preparations are available to fish farmers to treat disease or to eliminate parasites such as sea lice. These prescription-only medicines are applied under strictly controlled conditions, in line with regulatory authority rules and recommendations, and under the supervision of authorised veterinarians.

Mowi adopts a preventative approach to disease and health management through good husbandry and feeding methods, e.g. fallowing and introducing only healthy stock. Health strategies and good husbandry practices together with vaccination have now greatly reduced diseases. It is important to note that antibiotics are not given to promote growth, neither are any growth-promoting hormones used.

Mowi uses good husbandry and management, and safe and effective vaccines to minimise the need for medicines and will continue to seek ways of improving these practices. Mowi is actively involved, together with vaccine and pharmaceutical producers and other aquaculture companies, in the development of new vaccines and technologies. Where vaccines are not available, Mowi uses licensed medicines, in accordance with relevant regulations, to control outbreaks of disease. Any medicines that are used are authorised by the regulatory authorities when they are satisfied that the correct use of the medicines presents no risk to the operator, consumer, fish or the environment.

Authorisation specifies withdrawal periods and tolerance levels for residues, which must be observed prior to harvest. The Maximum Residue Limits for medicines, as specified by the EU, by the FDA in the United States, by the Food Inspection Agency in Canada and by the Japanese Minister of Health, Labour and Welfare among others, are implemented as the minimum requirement. These are equivalent to the conditions that apply to the use of medicines in other food animals.

The use of therapeutic substances in Mowi Ireland is only permitted for the treatment of diagnosed illness in fish and where fish welfare is compromised. There is no prophylactic use of antibiotics.

The use of allopathic treatments in Mowi Ireland is limited to two courses of treatment per year, with the exception of vaccinations and compulsory eradication schemes. If the mentioned limits for allopathic treatments are exceeded salmon cannot be sold as organic products. Only allopathic treatments approved by Irish regulatory authorities may be applied to fish.

The withdrawal period for allopathic veterinary treatments and parasite treatments including treatments under compulsory control and parasite eradication schemes is twice the legal withdrawal period as referred to in Article 11 of Directive 2001/82/EC or in a case in which this period in not specified 48 hours.

In accordance with Council Directive 96/23/EC, the Irish Department of Agriculture, Fisheries and Food under contract to the Food Safety Authority of Ireland, conducts annual monitoring of our fish for the presence of therapeutic residues, prohibited substances and other contaminants.

Mowi Ireland has a therapeutic residue absence policy. All fish stocks are screened for therapeutic residues prior to harvest. Copies of test certificates are available to customers on request.

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Are farmed salmon coloured artificially?

The pink colour of salmon flesh, wild or farmed, is caused by the presence of carotenoid pigments. These are known to be important in salmon and human nutrition, since they are important antioxidants.
The diet of wild salmon includes krill, zooplankton, small fish and crustaceans. Crustaceans and krill contain carotenoids that are absorbed by the salmon and deposited mainly in the muscle but also in the skin and in the eggs. The intensity of the colour varies between fish and does not seem to have an effect on the taste but it does enhance attractiveness to the consumer. There is evidence to show that there are several health benefits from the pigments for salmon and trout. Research shows that, due to astaxanthin's potent antioxidant activity, it may be beneficial in cardiovascular, immune, inflammatory and neurodegenerative diseases. Some research supports the assumption that it may protect body tissues from oxidative damage.There are more than 600 naturally occurring carotenoids and, for example, they produce the colours of carrots and of autumn leaves. The group of carotenoids found in fish are known as xanthophylls and include astaxanthin and canthaxanthin. As salmon are unable to synthesise these pigments, they must take them in as part of their diets. The pigments may come from crustaceans, from fermented yeast culture or, more usually, from nature identical products — all are approved by the European Commission and the FDA for addition to the diet of farmed salmon and of trout.

Fish health benefit. 

In the wild salmon it seems that the pigmentation has benefits in camouflage and in sexual attraction.  As female salmon prepare for breeding, the xanthophyll pigments are transported to the ovaries where they improve the maturation rate of the oocytes. The pigments become part of the yolk sac. When the eggs are released, the pigments have two further functions, protecting the eggs from damage by light and helping the male to find them. These pigments in the diet have been shown to increase the growth rate and survival of juvenile fish and are implicated in the synthesis of vitamin A in the fish.

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How does Mowi control predators taking its fish?

All animals that are farmed, including fish, have natural predators that will try to take stock from farms.Mowi acts to protect wildlife and takes a humane approach to animals that naturally prey on its fish throughout their growth cycle. The company policy is to discourage predators by employing a range of accepted and approved preventative measures, such as nets, which achieve a high rate of success while minimising damage to wildlife.

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How are salmon farms working to control sea lice?

Sea lice are naturally occurring ectoparasites (ectoparasitic copepods) of salmon and a range of other wild fish species. They occur on both wild and farmed salmon and horizontal infection occurs in both directions.

Through a combination of good husbandry and management techniques together with the use of wrasse grazing fish and medicinal control, sea lice infections on Mowi farms are kept to a minimum, for welfare, environmental and economic reasons. As a result, the spread of lice from farmed salmon to wild salmon is minimised.

Sea lice feed on the mucus and skin of the host fish. They are indigenous and were present long before fish farming started. Their presence is maintained through the wild population. When commercial farming began, the health status of the fish became important and it is much easier to monitor than that of the wild population. As a result, we are more aware of impact, biology and control of such pests on farmed fish.

Reducing the problem:

Active health monitoring programmes, including regular veterinary inspections, are proving to be a tool in limiting sea lice abundance. The magnitude of the problem is declining through modern husbandry and management practices and the latest biological and medicinal control techniques. These involve a combination of methods and preventative approaches. In areas of Scotland, Norway, Ireland and some areas in Chile, companies have arranged that whole loch/fjord systems be managed in a strategic and coordinated way thus reducing lice abundance and consequently the risk of infection within a body of water.


Mowi realises the importance of having safe and efficacious medicines available for the control of sea lice. As a major salmon farming company, Mowi provides open and unlimited technical support for the maintenance of existing products in each market and for the development of new products and technologies that will further improve lice control strategies.  In addition, Mowi is committed to efforts to limit discharge of medicines into the environment and maintaining environmental standards for sea lice medicines.

Biological control:

On farms in Scotland, Norway, Shetland and Ireland, indigenous cleaner fish, specifically wrasse, can be used to clean the lice from the salmon. These fish are sourced locally from sustainable fish stocks. Also, sites are left fallow (unoccupied and inactive) for several weeks. Without hosts, the lice population dies out. Both wrasse and fallowing are biological control methods.

Integrated pest management:

Mowi has put into place an internal procedure for Integrated Pest Management (IPM) and Resistance Management (RM) strategies. This follows a two-year internal development project. The procedure was designed to be compatible with and adaptable to the various national guidelines and programmes such as Norway’s Nasjonal Handlingsplan mot lus på Laksefisk (National Action Plan for Combating Sea Lice in Salmon Farming), in addition to Ireland’s National strategy for improved pest control on Irish salmon farms.

IPM and RM seek to incorporate good husbandry and management practices, to use biological controls and to optimise the use of medicines, including strategically timed and coordinated treatments. This provides efficacious control of lice while maximising the effectiveness of available medicines and prolonging their useful market life. At the same time it reduces environmental inputs and contributes towards a sustainable fish production system. The concepts of IPM and RM are formally promoted in several aquaculture areas where Marine Harvest is farming, including Ireland.

Multi-party projects:

Mowi has been an active partner in several projects related to sea lice and their control, where new tools and processes have emerged, and which have been utilised and harmonised to optimise strategic lice control. These projects have included investigations into sea lice epidemiology, sea lice resistance, optimal use of wrasse and the interaction of lice between wild and farmed fish.

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Do salmon escape from farms?

Escapes from salmon farms are a very small percentage of the total number of salmon in farms but the numbers can seem potentially significant.

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What emergency measures are you putting in place to ensure your fish do not escape?

The loss of salmon stock represents a financial loss to our business so we take every measure to ensure that it does not happen. That is why we have a zero tolerance policy on escapes. We invest in the very best infrastructure, nets, moorings and monitoring technology and they are inspected and replaced regularly, it is something on which we put a lot of emphasis.

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What impact would a release of your fish into the local waters have?

Wild and farm-raised Atlantic salmon are virtually genetically identical. However, there is a difference in their behaviour. Wild salmon are predatory and used to finding food. Farm-raised salmon are not used to hunting for food and thus often fail to survive in the wild. Some farm-raised salmon may be tough enough to survive in the wild, allowing them to breed with local wild stocks.

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How much stock have you lost over the years from your other locations?

In over forty years we have had three stock losses in Ireland. In 2017 we lost 20,000 fish from one pen in Glinsk, Co. Donegal during net changing procedure. In 2010 we lost a total of 85,073 fish from one pen in Donegal Bay which was damaged during a force 10 gale with 125 km/hr westerly winds. Prior to that, our last loss was in 1995 in Lough Swilly when we lost fish after storms. Since these occurrences we have upgraded the design of the pens on all of our farms.

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Is fish farming causing algal blooms and shellfish poisoning?

There is absolutely no link or scientific evidence between salmon farming and any blooms which impact on shellfish. Algal blooms are natural phenomena, which have been linked to rising sea temperatures. Shellfish poisoning is caused by toxins that are generated during the algal bloom and then accumulate in bivalve shellfish such as scallops as they filter the water.

Algal blooms can also cause problems to fish. Some species may produce potent toxins such as neurotoxins, others physically clog the gills, leading to damage and in some cases to death by asphyxiation (suffocation). The algae can also reduce the available oxygen in the water.

The toxins concerned and all three forms of shellfish poisoning they can cause; amnesic, diarrhoeic and paralytic, have been known as long as man has been eating shellfish. The algal species concerned have been identified in fossil records. Not eating shellfish in the summer months and purging in clean water have been standard practices for many decades.

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Are salmon kept in crowded conditions?

Mowi sees no conflict between commercial interests and taking a humane and enlightened approach to salmon production. The health of salmon and other farmed fish demands a pure and stable environment, a balanced and healthy diet and freedom from stress. There is a direct link between the standards of husbandry and the high quality products that consumers demand.  Keeping farmed fish in overcrowded conditions would be counter-productive even if the company had no interest in animal welfare. In fact, Mowi holds animal welfare to be an important consideration in all its activities. The actual stocking density on a Mowi salmon farm compares favourably with other livestock production systems, partly because it is three-dimensional — with the fish able to move vertically as well as horizontally.

Mowi Ireland specified stocking densities for organic salmon are less than 10 kg per cubic metre (1,000 kg of water). This means that even at maximum stocking rates the fish occupy less than 1% of the pen volume and have more than 99% of the space for free movement. Although they have this space available, the fish often congregate and swim together, as a shoal.

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What is your environmental record?

Fish farms are extremely tightly regulated and regularly audited under environmental, food safety, navigation, fish health, water quality, health and safety, feed controls, residues, seabed quality, equipment standards, etc. by no less than eight different state organisations in Ireland. Breaches of any statutory standards are treated very seriously. In addition, the most important link in the business chain – the customer – also employs independent auditors to examine operations, quality and environmental standards at regular intervals to ensure Irish salmon remains in its place at the top of the league of quality fish on the supermarket shelves.

Salmon farming is dependent on a clean and healthy environment. We were Ireland’s first primary food producer to be certified under ISO 14001:1996 (International Environmental Standard). Our focus is on environmental responsibility. We make every effort to ensure that we do not disturb the ecological balance at our sites by maintaining secure fish stocks and by ensuring that only environmentally sound products feed and treat our fish.

In March 2015, Mowi Ireland announced that it attained Aquaculture Stewardship Council (ASC) salmon standard certification which is one of the highest international environmental and social sustainability standards in the fish farming sector. The standard was obtained for our sea site at Deenish Island in Ballinskelligs Bay, Co Kerry which is the first ASC salmon standard held by the company.

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How safe is farm-raised salmon?

Our farm-raised salmon is a premium quality food product that is both enjoyed and in demand from the most sophisticated markets in Western Europe, like Germany, Switzerland and in the US also, it is a very high value premium food product.

Ireland has the best reputation in the world for fish health, with skilled veterinarians and biologists assigned to care for our stocks, a very public reporting system in place since the early 1990's (which other countries are only now following) and the recent production of a new national fish health handbook which was recently reviewed by over 40 experts and industry at the Marine Institute. It can be found through this link.

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What do you feed your farm-raised fish?

Our organic feed is made of a combination of fishmeal, fish oil and/or vegetable meal and oil which is mainly made from sunflower, soy and rapeseed. As we use wild fish trimmings of fish for human consumption there is no waste. This is without doubt the most efficient and most sustainable method in the world of protein production.

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Who regulates the fish-farming sector in Ireland and how is it regulated?

Ireland has a very stringent and strictly enforce regulatory regime for aquaculture, regulation is enforced through the Department of Agriculture, Food and the Marine. In addition as our salmon farms are classified as organic there are additional independent audits undertaken annually to ensure the highest organic standards are maintained.

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Are sea lice from your farms killing wild fish?

No, we do not believe they are. In Ireland there have recently been two comprehensive and independent published papers by the Irish Marine Institute (see links below) which conclude that salmon farming does not have an impact on wild salmon. It is also interesting to note that there are no salmon farms on the east coast of the country but rivers remain closed to angling because stocks are critically low yet on the west coast where there are a number of farms angling continues due to their abundance.

We have implemented tried and tested operational procedures to control sea lice. Through our experience we have learned that the management of sea lice is best handled through a combination of medicinal treatments, fallowing of sites as well as good production management and stock rotation between a number of sites.

Paper one :
Impact of early infestation with the salmon louse Lepeophtheirus salmonis on the subsequent survival of outwardly migrating Atlantic salmon smolts from a number of rivers on Ireland's south and west coasts.

Paper two :
An evaluation of the impact of early infestation with the salmon louse Lepeophtheirus salmonis on the subsequent survival of outwardly migrating Atlantic salmon, Salmo salar L., smolts

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