Aquaculture in the United Kingdom is dominated by salmon farming (mostly in Scotland), then by mussel production with trout being the third most important enterprise. Aquaculture in the United Kingdom represents a significant business for the UK, producing over of fish whilst earning over £700 million in 2012 (€793 million).Values given are for 2012.
UK aquaculture applies to three main strands of species; finfish (salmon, trout, carp etc.), shellfish (mussels, oysters, lobster etc.) and marine algae (seaweed). These are rated in the tonnage that is produced annually. Aquaponics involves the symbiotic relationship of fish farming with growing plants in water (a process whereby the plants clean the dirty water from the fish tank). As such, aquaponics is not included in this article. A fourth strand is ornamental (coldwater fish, tropical fish and aquatic plants), but this is in very small volumes by weight.
Scottish finfish aquaculture is rated third in the world behind Norway and Chile in terms of tonnage of production, and is the United Kingdom's most valuable food export. Aquaculture is also increasingly being used to help conserve rare species where breeding grounds have been destroyed or other environmental factors have affected reproductive patterns.
Overview Historically in the United Kingdom, as in other European nations, the keeping of fish in ponds for use as food dates back centuries, possibly as far as the 13th century. A fish pond was a way of keeping a steady supply of food through the winter, and most medieval and monastic houses and castles had a fish pond stocked with carp, pike and bream. Some were vastly under-utilised and the efforts of keeping fish was to serve up only on special occasions, especially in monastic houses, when freshwater fish would be avoided at Lent. During the 19th century, as fresh sea fish could be brought from ports to inland locations by the railways, the stocking, breeding and farming of fresh fish declined, unlike eastern European nations where the carp is still a 'table fish'.
The aquaculture industry in the United Kingdom is dominated by the farming of Atlantic salmon (mariculture), which is concentrated in the shoreline waters around Scotland. Smaller aquaculture business include seaweed farming in Yorkshire and Cornwall and the shellfish industry in Wales. Salmon farming in Scotland started production in the early 1970s and the number of companies increased exponentially. Even though the number of farming sites have been increasing, the number of different companies has decreased; in 1995 62 companies operated 162 sites between them, by 2016, 254 sites were in operation overseen by just 16 companies. By 2019, only 12 businesses were in operation at what was described as "226 active sites". The tonnage of salmon production from Scotland in 2017 was , which makes Scotland the third largest producer behind Norway and Chile. However, concerns with the detrimental effects of fish farming on the fish themselves, the wild fish and the immediate environment that they habit and cohabit, has led to some criticism from wildlife groups and academics.
99% of finfish production is from Scotland, whilst 47% of shellfish production comes from England and Wales. The Centre for Environment, Fisheries and Aquaculture Science (CEFAS), has over 500 business registered in England and Wales for finfish aquaculture, though most of these are breeders of fish for ponds and indoor tanks. Producers can apply to become members of the BAP (Best Aquaculture Practice), which guarantees responsibility and certification for every step in the production chain.
The second largest aquaculture market in terms of tonnage is the shellfish market, mostly mussels, but also oysters and scallops. The abalone Haliotis tuberculata, known as green ormer in the UK, is increasing possible to be farmed in the coastal waters of the southern half of the United Kingdom due to global warming, and some trials have taken place on the south west coast. The ormer does not suffer the effects of pollutants, and more importantly, does not store toxins in its flesh unlike other bivalve creatures.
Salmon
Scotland Salmon farming on a commercial scale was started in Britain by a company called Marine Harvest, then a subsidiary company of Unilever. Marine Harvest had invested in two sites in the 1960s, a salmon and trout farm in Lochailort, and a flatfish and crustacean research centre in Findon, just outside Aberdeen. The first fish production from Lochailort was achieved in 1971, since then the industry has expanded and salmon and trout are farmed commercially in Scotland at sites in Argyll & Bute, Highland, Orkney, Shetland and the Western Isles.
In 2014, fish farming in Scotland led to a turnover in the country to the tune of £1 billion, and supported over 8,800 jobs. However, diseases, and parasites such as the sea louse, have had a detrimental effect on the industry and have led to many different ideas on how to combat the parasite. Mortality rates of salmon during the 1990s and 2000s was rated at about 20% of eventual production tonnage. The indications are that this percentage is increasing. Companies have been moving away from using chemical and water washes to rid the salmon of lice, with a more 'natural' method being the use of wrasse and lumpsucker fish which clean the fish of the parasites.
Additionally, the increase in production has led to waste produced by the salmon settling on the sea-bed of the Scottish sea lochs. Companies have been trying large storm-proof cages that can be deployed further out to sea, thus the current will spread the waste over a larger area. Another benefit of the cages is that the stronger currents will make the salmon swim harder and increase their muscle tone, which makes them comparable to wild salmon. The Scottish Environment Protection Agency has indicated that providing the newer farms further out to sea meet the standards required "on chemical, faecal and organic waste pollution in surrounding seas", it would not place a restriction on these newer farms.
Salmon farming has also led to criticism from wildlife groups, conservationist and anglers, all of whom point to lower levels of wild salmon swimming up river to spawn. They allege that the mass proliferation of sea farming methods has had a detrimental effect on the wild salmon species. One journalist pointed out that a cage could hold up to 70,000 fish, which he said was the equivalent of "..a series of floating battery hen sheds; salmon has long been sold on the prospect of cleanliness and health. The impression is fraudulent."
A Parliamentary committee raised the possibility of salmon farms being located on land to avoid the prevalence of sea lice. One speaker at the committee's hearing stated that they were spending £50 million to produce of fish, and that the added cost of building concrete structures to house the fish would cost extra and would be power hungry, therefore negating the benefits of having open pens/cages in the sea.
Due to the large number of salmon migratory rivers on the east coast of Scotland, no salmon farms have been allowed to be sited in that area.
In 2025, The Food Policy Institute called for a moratorium on new intensive fish farms in Scottish sea lochs, pending compliance with environmental and welfare standards and giving the Scottish Government time to audit, monitor properly, and adapt regulation.
Northern Ireland In 2007, the only salmon farm on the coast of Northern Ireland lost all its stock of 100,000 fish when a swarm of "billions" of jellyfish (mauve stingers pelagia noctiluca) got into the nets and killed them all. A similar event occurred in 2014 at a fish farm in Loch Duart on North Uist. The jellyfish is small enough to get into the pens holding the salmon, but its usual habitat is further south in the Mediterranean. Scientist have stated that is appearance in UK waters is a sign of global warming. The company restructured in 2008 and was able to achieve production in 2009 under a different name. It advertises itself as being an organic farm and is spread across two sites at Glenarm and Red Bay in County Antrim.
Like their Scottish neighbours, the location of farmed fish has been cited as the reason for the drop of wild salmon migrating upriver to spawn. A monitoring station on the River Bush has found that numbers of migrating fish have dropped by a third in some years.
England and Wales Minimal salmon farming is undertaken in Wales. In 2012, a total of of finfish were produced in Wales, however, this also accounts for trout, turbot, carp and goldfish which makes the amount of farmed salmon quite small in comparison with Scotland. However, the tonnage and relative price of the salmon market makes salmon the most valuable food item in the United Kingdom that is exported and which supports a network of jobs in rural areas. Most salmon farming in England is at designated hatcheries which then release the juvenile fish (smolts) into designated salmon rivers.
Mussels The production of mussels in the coastal water around the United Kingdom is likely to be affected by climate change. A Government report in 2018 estimated that a temperature rise in seawater could lead to a reduction of 50% in mussel aquaculture. One variant of mussel aquaculture is less labour-intensive than other aquaculture strands as growers simply install lines in the sea and wild mussels attach themselves to the lines feeding off naturally occurring plankton. All the grower has to do is harvest the mussels at the right point in their growing cycle. However, in North Wales, the farmers are constantly moving their mussels along the sea-bed to deeper and deeper water to promote growth.
The global mussel market is worth over £1.5 billion annually (2018) and represents the largest tonnage in Europe, but the second largest after salmon aquaculture in the UK.
England Mussels are farmed offshore in Cornwall and Devon. One site off the coast at Brixham, (the largest in England which covers over ) was the first mussel farm in Europe to gain Best Aquaculture Practice certification. Another mussel farm in Cornwall is located in St Austell Bay and also supports one of the seaweed farmers and is a release point for lobsters from the Padstow Lobster Hatchery.
Scotland In 2018, the Scottish industry produced of mussels with a value of £7.8 million. The bulk of mussel production comes from Shetland, and the Western Isles. No shellfish are farmed on the eastern coast of Scotland.
Mussel farming is a large industry in Scotland, one company has 14 sites and provides over 70% of the mussel crop from Scotland every year.
Wales Mussels are farmed in North wales around the Menai Strait and Conwy. Small mussel farming also takes place on the coast of South Wales. Around the Menai Strait, the mussel farmers use boats to capture young mussels and they site them in the intertidal zone which dries out at low tide. This prompts hard shell growth, and as they get bigger, they are moved further offshore until they are submerged all the time which prompts body mass build-up. The vast majority of mussels exported from the United Kingdom are from the mussel farms in North wales.
A proposal to create a tidal lagoon in Swansea Bay to create electricity would have provided a perfect site to farm mussels. Although the project was shelved by the UK Government, in early 2019, the company behind the idea was still hoping it would come to fruition with other investment. A report commissioned by a local oyster company detailed the possibility of farming mussel, native oyster, pacific oyster, the European clam and macroalgae (seaweed).
Other shellfish