Scottish Fish Farming and Aquaculture Industry

In 2018 a report entitled The State of the World’s Fisheries was released by the Food and Agriculture Organisation of the United Nations. The report revealed that the amount of fish being produced across the world was steadily rising, despite the capture levels of wild fish remaining static since the 1980s. The reason for this was the huge increase in the production farmed fish (a process also referred to as aquaculture). Indeed, fish farming accounted for 53% of the 171 million tons of fish which was produced worldwide in 2016 making the global aquaculture industry worth $232 (£189 billion) (1). China is by far the biggest producer of fish from aquaculture in the world, raising 66.8 million tons in 2016. India and Indonesia were also major producers, both generating over 10 million tons, while the only European countries rank towards the top of world fish farming are Norway and Russia, producing 3.3 and 4.9 million tons respectively.

The Fish Farming Process

Aerial picture of an open water salmon farm © cookelma / 123RF Stock Photo.

While there are a number of different types of fish farms, all of which operate in a different way, the process is generally as follows. Salmon are hatched in freshwater and grown to around 100 – 200 grams (up to 7oz) in weight. They are then transferred into open water pens in inshore marine environments where they remain until they have grown to 4 – 5kg (8 – 11lbs), which may take up to three years. Once they have reached this marketable size they are transported to a fish processing plant where they are killed and prepared for sale and finally sent on to retailers and wholesalers.

Meeting the Global Demand for Fish

Fish farming has expanded across the world to meet the rising demand for fish. On a global average the consumption of fish has risen from 9kg per person in 1961 to 20.2kg in 2015, and demand for fish for non-food uses such as fish meal and fish oil has also increased significantly (1). With wild capture rates remaining steady since the late 1980s – and many natural fish stocks across the world in decline – it has been fish farming which has been able to ensure that the growing worldwide demand for fish has been met. While it has been Asian countries which are responsible for the huge global increase in fish farming – China has produced more artificially produced fish than the rest of the world combined since 1991 – Britain, or more specifically Scotland, has also seen increased levels of fish farming. This has mostly been seen in Scottish salmon farming which has grown from a small industry in the 1970s to one which exports around £600 million of seafood to more than fifty countries each year.

Scottish Fish Farming – A Success Story?

The growth of the Scottish salmon farming industry has been hailed as a success story by many within Scotland. Scottish salmon has an extremely good reputation across the world, making it a premium food with prices to match. This high reputation was underlined when, in 1992, Scottish salmon became the first ever fish (and first ever non-French food) to be awarded France’s Label Rouge for foods which “specific set of characteristics establishing a superior level to that of a similar current product” (2). Furthermore, in many remote and rural areas of Scotland the expansion of the salmon farming industry was seen as a way or bringing jobs, regeneration and investment to remote rural communities.

A perfect example of this was the Isle of Muck, the smallest of the Small Isles of the Inner Hebrides. With a population of just forty people the island had no permanent shop and relied on seasonal tourism as its main source of income. In 2014 the Norwegian-owned company Marine Harvest (now known as Mowi) built a relatively small salmon hatchery on the island as part of an £80 million expansion (3). As well as creating ten permanent jobs the company improved roads on the island and built houses for its staff, many of whom have now relocated to the island with their families. In 2018 Marine Harvest applied to expand the fish farm on the Isle of Muck, stating that this would increase processing power and support three new full time jobs (3). With salmon farming being used to renew communities and provide employment and investment in areas which would be ignored by most other employers it is easy to see why the Scottish fish farming industry has received significant political backing from the governing Scottish National Party (SNP).

Overall fish farming directly employs several thousand people across Scotland. While this may sound like a fairly inconsequential figure the jobs are, as discussed above, often in areas which have low levels of employment and require investment in both employment markets and infrastructure making these jobs disproportionally important. The relatively low number of direct jobs, however, does lead to a much higher number of jobs in the wider supply and transport chain, meaning than investment in fish farms can bring much higher economic benefits to an entire region. The entire Scottish fish farming industry adds £1.8 billion to the nation’s economy each year and the official Scottish government website states that it supports plans to double the economic contribution of Scottish aquaculture to £3.6 billion by 2030 and double the number of jobs supported by the industry to 18,000 within the same timescale (4).

Expansion and Resulting Problems

Due to its ability to generate huge sums of money and breathe new life into economically struggling regions the Scottish fish farming industry has expanded rapidly over recent years. In 2017 the industry produced 189,707 tons of Atlantic salmon, a record amount which was up 16.5% on the previous year. The breakneck speed of the expansion has led to questions over the environmental impact that fish farming has on the environment being downplayed until very recently. Indeed, many organisations and politicians have been proud to talk up the economic success of Scotland’s salmon production and exports, but a lot less keen to discuss the environmental, pollution and animal welfare concerns which are becoming increasingly prominent across the industry.

Waste and pollution: One of the main issues with Scotland’s salmon farms is that the salmon are not grown in tanks on land, but are instead held in open water pens located in inshore areas, each of which can contain thousands of individual salmon. This means that the large amounts of waste produced by the salmon, as well as uneaten food, are left to pollute the surrounding water. A report by Dr Robert Luxmoore, senior nature conservation advisor to the Natural Trust for Scotland, found that a single, moderately sized fish farm produced the same amount of waste as all of the towns on the west coast of Scotland combined (5). He added that waste produced in towns was treated, but all of the waste produced by fish farms directly entered the sea.

Escapes: The open water location of salmon pens also leads to the problem of escaping salmon. This is a major cause of concern as escaped farmed salmon can spread parasites and disease into wild populations. Tens of thousands of farmed salmon can escape into the wild when predators such as seals tear open salmon pens. The impact that escaped salmon have on wild populations is not entirely clear, but there are fears that genetic mixing may occur when escaped farmed salmon breed with wild salmon, affecting the genetic makeup of natural populations and possibly weakening their homing instinct. Scottish fish farms have long been blamed for destroying stocks of wild salmon – a species which is worth a huge amount to the economy through the recreational angling industry. This theory was given further weight in 2019 when news emerged that wild stocks of Scotland’s salmon were at the lowest levels since records began in 1952 (6). This has led to Fisheries Management Scotland to state that wild salmon stocks are at “crisis point” and organisations such as Salmon and Trout Conservation Scotland blaming open water salmon farms for the reduction in wild stocks (6).

Parasites: Another major issue with salmon farms is parasites – specifically Lepeophtheirus salmonis, the common sea louse. This is a small copepod which grows to a maximum size of around 15mm in length and mostly affects trout and salmon species. It attaches itself to the scales, gills or fins of a salmon and feeds on the skin of the fish. While small numbers of lice are not likely to be fatal to a salmon they can damage the fins and scales and make the salmon unfit for sale. Large numbers of lice can kill salmon, and even small infestations can leave open wounds on salmon which lead to further infection and eventual death. The way salmon are housed in extremely close proximity when held in artificial conditons provides an ideal breeding ground for sea lice and means infestations can spread extremely rapidly. The Guardian has reported that the Scottish salmon industry alone has spent over £300 million trying to treat salmon and eliminate sea lice infestations, and a “chemical arms race” has developed as fish farms use increasingly toxic pesticides and antibiotics to try to rid salmon of lice (7). While the industry claims that sea lice are a natural occurrence and chemicals used to treat them degrade quickly once released into the sea the reality is that due to the open water nature of fish farms huge amounts of chemicals are released into the sea when salmon are treated for sea lice infestations. In 2017 SEPA (the Scottish Environmental Protection Agency) released information under the freedom of information law about the impact that chemical treatments by fish farms had on the marine environment. The data revealed that between 2006 and 2016 chemical use breached environmental safety limits more than one hundred times (8). It also found that anti-sea lice pesticide found in sediment was at a greater level than environmental quality standards allowed in forty-five sea lochs and inshore coastal locations (8). The main pesticide found was emamectin benzoate which SEPA said was “toxic to birds, mammals, fish and other aquatic organisms” and in humans it could “cause irritation of the respiratory tract, eyes and skin” (8).

Cleaner fish: The problems caused by chemical treatments have led to salmon farmers looking for natural and less damaging ways of ridding salmon of sea lice. One which has proved effective – although incredibly damaging for wild fish stocks – is the use of so-called ‘cleaner fish’. These are fish, usually wrasse or lumpsucker, which are caught in the wild and then transported to Scotland’s fish farms. They are then placed into the water with salmon where they will naturally feed on the sea lice, picking them off salmon without harming the salmon in any way. The use of wrasse and lumpsucker to rid salmon of parasites is often promoted as a “natural solution” (9) to the sea lice problem, and is an area which the Scottish salmon farming industry has invested significant funds into. The reality is that huge amounts of wild wrasse are trapped to supply Scottish salmon farms with cleaner fish, usually from the coastline of south west England. An article on the BBC website in June 2017 stated that around three million wrasse were needed to supply the Scottish fish farming industry with cleaner fish, but only 600,000 wrasse were raised in farms, with the rest caught in the wild (9). Many anglers will be horrified that millions of wild wrasse are being taken from the sea to supply Scottish fish farms, with campaign groups such as Open Seas warning that there have been no stock assessments for wild wrasse, and there are no limits or regulations on how many can be taken for use in fish farms (9). The Scottish Salmon Producers Organisation have claimed that they are opening new wrasse hatcheries and will only use artificially raised wrasse to supply fish farms with cleaner fish from 2021 or 2022. But, as wrasse are a slow growing and late maturing species, there are fears that huge damage will have been done to wild wrasse stocks, especially around the south west of England, before a farmed supply of wrasse has become established. There are signs that communities are turning against the capture of wild fish to be used as cleaner fish. In 2019 the Channel Island of Sark became the first part of the British Isles to ban the capture of wild wrasse for the purpose of stocking fish farms with cleaner fish (10).

SealShooting seals and acoustic deterrence devices: There has also been concern and pressure from animal welfare groups over the way Scottish fish farms shoot seals and use acoustic deterrence devices to keep seals away from fish pens. The Scottish Salmon Producers Organisation says that seals damage nets and pens and can cost the industry over half a million fish per year (19)., meaning that it is necessary to control seal numbers and stop seals from preying on the farms’ fish. Acoustic deterrence devices (ADDs) which emit loud underwater sounds are also used to keep seals away from fish farms and open water pens, although there is concern that they may impact on the hearing and navigation of all marine mammals including endangered dolphin and whale species. Animal welfare charities and environmental groups have condemned the shooting of wild seals and the use of ADDs, and both may be banned from 2021 in Scotland (19).

Sandeels: The salmon farming industry has also been blamed for the decline in sandeels. The various species of sandeel found in the waters around the UK are hugely important for the entire marine ecosystem. For predatory species such as mackerel, pollock, coalfish and bass they are a key source of food, but almost all of the species of fish found in British waters will feed on sandeels at some point in their life, as well as a wide range of marine birds. Although they are not consumed by humans, sandeels are highly commercially important as they are turned into fishmeal and animal feeds. They can be used to feed livestock such as pigs, but their main use is to feed the growing number of farmed fish around the world. The Danish fishing industry controls the vast majority of fishing for North Sea sandeels, having a quota to catch 458,000 tons of sandeels each year, a figure which was reached after the EU allowed the Danes to increase their quota from 82,000 tons in 2017. The use of wild caught fish to feed farmed fish is highly controversial, as it is estimated that on average 3kg of wild caught forage fish is needed to raise 1kg of marketable farmed fish (11). The huge levels of small fish being taken from the sea by the commercial fishing industry has been blamed for the 70% decline in seabirds around the UK since the 1950s, with scientists and conservationists arguing that these species of birds simply cannot cope with the increased competition there now is for food. There is rising awareness of the how the entire marine ecosystem around the British Isles will be affected if sandeel and small forage fish stocks are allowed to be overexploited to supply fish farms with feed.

Fish Welfare and Mortality: The welfare and mortality rates of artificially raised salmon has long been an issue which campaigners have been concerned about. In 2015 inspectors from the Scottish government investigated the conditions which salmon were kept in across a number of fish farms along the west coast of Scotland. Photographs taken by the inspectors were later released by the Scottish government under a freedom of information request and published by the independent news outlet the Ferret. Dubbed “horror photos” by the Ferret the pictures showed salmon suffering from “bloody lesions, eye damage, deformed organs [and] plagues of flesh-eating sea lice” (12). It was also revealed that the inspectors had found “severe lice damage to their heads” and a “high lice burden” in fish they examined in their sample. Other issues encountered included fish with “no eyes”, “gross haemorrhaging”, “deformed hearts”, “enlarged spleens” and “necrotic gills” (12). The release of the photos led to calls for legal action to be taken against fish farms due to the standards of welfare they provided for the fish they produced, and there were also calls for a consumer boycott. The Scottish government said that the photos needed to be viewed in context and were not representative of the overall health of salmon raised in Scotland (12).

It was also revealed in a later edition of the Ferret that two fish farming companies appealed to ministers to block the release of the photos due to the “reputational damage” that the images would cause. In 2018 UK fish farms were required to publish monthly mortality rates for the first time. Almost two-thirds of farms had less than 1% mortality, but one farm lost 19% of its salmon when it was struck by a storm. Another lost 58% of its fish when it was struggling with an infestation of sea lice. In December 2018 news emerged that Wester Ross salmon farm had lost 52.8% of its salmon at one site, and 41.9% at another (13). The cause of the deaths was the extremely hot weather which led to high levels of plankton and plummeting levels of oxygen in the water. This caused “irreparable damage” to the gills of the salmon, leading to the deaths. The farm reported that the surviving salmon had recovered well (13).

Pressure for Reform and Change

In early 2018 the Scottish fish farming industry was dealt a blow when a report commissioned by the nation’s Environment Committee concluded that Scotland’s marine ecosystem faced “irrecoverable damage” if environmental concerns over salmon farming were not addressed (14). The report also stated that little progress had been made in tackling environmental issues brought about by salmon farming since 2002, and there was ineffective and insufficient regulation of the nation’s entire aquaculture sector. Campaign groups saw the report as confirmation of their claims and concerns, while representatives of the fish farming industry pointed to investment in “new innovations” and research which would address the problems facing the industry (14). In October of the same year a report by SEPA (Scottish Environmental Protection Agency) found that 56 of the country’s 297 licenced fish farms were rated “poor”, “very poor” or “at risk” due to not meeting environmental standards, with pollution and unregulated levels of uneaten fish food and fish faeces being found on the seabed around the farms being the main reason for the poor grading.

The criticism of Scotland’s fish farming industry has led to calls for the expansion of aquaculture to be halted. The National Trust for Scotland has asked Fergus Ewing, the Cabinet Secretary for the Rural Economy, to ban further fish farms from being built until environmental concerns are addressed, and expressed concern that government-backed plans to double production of farmed fish were set to go ahead. The call to halt the expansion of fish farms has been backed by environmental groups.

It does appear that environmental concerns over fish farming are beginning to have an influence on government policy. In November 2018 the BBC reported that SEPA were proposing much tougher rules governing the way fish farms operated. New regulations would limit the amount of liquid based medicine and chemicals which could be put into the water to treat salmon, and some salmon farms could be forced to close due to the impact they were having on the local marine environment (15). Others would be made to relocate out of inshore areas and into deeper water with stronger tides and faster flowing water to prevent waste and fish faeces from accumulating in the waters around the farm (15).

Fish farm off the coast of Skye.

There are also appears to be many more objections and greater debate when plans are made for new fish farms to be built. This could be seen in 2019 when plans for a fish farm (again ran by Mowi) off the Hebridean island of Canna were opposed by the National Trust for Scotland, even though this would be an “organic” fish farm which contained far fewer fish and therefore produced less waste and pollution than a traditional fish farm. The National Trust for Scotland said that the fish farm would “undermine, if not destroy, the very things that make Canna so important” (16). At the time of writing [March 2020] it had still not been decided if the Canna fish farm was to go ahead.

In fact the concern over Scottish fish farms has grown to such an extent that protests against the industry by environmentalists and concerned citizens have taken place. In September 2019 around 200 people turned up to create a human chain to protest against plans to create a large salmon farm in a protected area on the north-east coast of the Isle of Arran (17). The previous month Scottish newspapers such as the Herald reported that a plan had been devised for a direct action protest to take place against the farms which have been built along the west coast of Scotland. This would be carried out by swimmers, kayakers and divers encircling the pens of the fish farm. In order to draw attention to the protest some of those taking part would be wearing fancy dress including “a lobster in a gas mask and a seal in bullet proof vest” (18). It remains unclear if the protest actually took place as no media outlets have reported on it.

BBC Panorama Episode May 2019

On the 20th May 2019 an episode of Panorama covering the Scottish salmon farming industry aired on BBC 1, exposing the problems associated with salmon farming to a much bigger audience. In this episode the reporter explained that Scotland has more than 200 salmon farms, producing tens of millions of salmon each year. A marketing expert explained that salmon were part of ‘Brand Scotland’ which allowed salmon to be sold at a higher price due to the history and perceived quality of the product. However, the issues affecting the salmon farming industry which are outlined in this article were described and discussed, and the BBC calculated that the Scottish salmon farming industry has a mortality rate of 20%, equating to 9.5 million fish dying each year. The programme also contrasted Scottish salmon farms with those of Norway which are much cleaner and less polluting due to innovations such financial incentives for farms to use closed and semi-closed pens which prevent waste and chemicals from entering the sea. Although this was not mentioned in the programme it may be the case that the expense involved in meeting Norway’s high standards of fish farming is a reason why Norwegian aquaculture companies have invested in Scotland where the fish farming regulations are much less stringent.

The Future

It now appears that the industry is beginning to accept that it can no longer take a ‘business as usual’ approach to the way fish farms operate and must begin to address the very real concerns over the impact that fish farming has on the marine environment. The ongoing expansion of the Scottish fish farming industry also has to stop, or at least be paused while reforms are made to ensure that fish farms operate in a less destructive and damaging manner. The Scottish government’s official line that the output of the nation’s aquaculture industry will be doubled by 2030 is now looking increasingly out of step with their claims to be world-leading when it comes to stewardship of the environment. Other issues, such as the worrying decline of Scotland’s wild salmon stocks also look impossible for Holyrood to ignore.

Scottish Parliament Building
Politicians in the Scottish Parliament have begun to take a tougher line on the regulations and rules the nation’s fish farms must follow.

In 2020 some progress was made towards tightening regulations which Scottish fish farms must adhere to. The Scottish government announced that ministers would work pass legislation to ban fish farms from shooting seals by 2021 (19). Pressure from environmental groups and a potential ban on exporting farmed salmon to the USA were believed to be the main reasons behind the ban (19). Acoustic deterrence devices would also be banned as there was evidence that they had an impact on whales and dolphins which would make their use incompatible with legislation which was in place to protect marine mammals.

Furthermore, there is a growing public awareness of the environmental concerns surrounding fish farming. Supermarkets which stock farmed fish are now coming under pressure to ensure that the fish they sell is provided from sustain(able fish farms which do not deplete forage fish stocks to feed their fish (21), and supermarkets which fail to do this are being named and shamed. In March 2020 Iceland and Aldi were named as the bottom two supermarkets for supplying sustainable fish as they sold farmed fish which had been fed with high levels of wild-caught fish (21). There is evidence that the Scottish government may already be learning lessons for the mistakes made in the expansion of the nation’s fish farming industry and taking a more circumspect approach when it comes to exploiting the nation’s marine resources. In 2018 an Ayr-based company called Marine Biopolymers planned to “sustainably harvest” wild kelp off the west coast of Scotland. This was blocked by the Scottish government and a wide-ranging review of all aspects of kelp harvesting was commissioned and would have to be completed before any company could begin commercially collecting kelp from the Scottish coastline (22). When contrasted with the rapid speed at which the fish farming industry was able to expand this shows a much more cautious and careful process is now taking place when it comes to commercial activity which could have an impact on the marine environment.

A protest against Scottish fish farms in 2019.

Technology may hold the answer to reducing some of the most damaging aspect of modern aquaculture. Norwegian company CageEye has developed a system for farmed salmon which uses advanced hydro-acoustic technology to monitor the sound made by feeding salmon. Once the salmon have stopped taking food the noise they make decreases and the system will then automatically shut off the food supply, reducing the issue of waste food polluting the water. A different automated system called Stingray is also be developed which may eventually be able to remove parasitic lice from salmon using lasers (23). The extent to which fish farms around the world will be willing to invest in such complex technology remains unknown. Unconventional ideas have also been put forward, such as the idea of using sea cucumbers underneath fish pens to consume waste products and uneaten food which are produced by the salmon (24). While such methods have proved effective in fish farms in Asia further research will be needed to see if they can be used by Scottish fish farms.

Graph showing how the amount of wild caught fish has plateaued since the late 1980s but the amount of fish produced by aquaculture has increased steadily during the same time period (source: Food and Agriculture Organisation of the United Nations.

Despite the problems faced by the industry the Scottish fish farming industry is still very powerful and well-funded and retains significant political backing. This is matched by a strong political will in Europe to continue to expand fish farming across the continent. In November 2018 Marco Gilmozzi, the president of the Federation of European Aquaculture Producers, said that the continent’s aquaculture industry had to be “ambitious” and aim to near double production from 2.3 million metric tons to 4.5 million metric tons by 2030 (25). He also said there was a need to “reduce bureaucracy and licensing times” in the European aquaculture industry (25). With such powerful figures appearing wilfully blind to the issues which are confronting fish farming and seeming determined to aggressively expand the output of the fish farming and aquaculture industry securing the far-reaching reforms which are needed may prove extremely difficult. In February 2021 a report entitled Dead Loss was compiled by Just Economics for the Changing Markets Foundation. The report stated that globally the damage and pollution caused by fish farming cost around $50 billion (£35.8 million) between 2013 and 2019 (26). In Scotland, the cost of fish farming in environmental terms was £1.4 billion between the same years (26). Such news will continue to emerge as the environmental impact of fish farming becomes apparent, although the extent to which it limits and reduces the expansion of the Scottish salmon farming industry remains to be seen.


  1. Food and Agriculture Organisation of the United Nations – The State of World Fisheries and Aquaculture: Meeting the Sustainable Development Goals, 2018.
  2., Label Rouge, 25 March 2015.
  3. The Press and Journal, Marine Harvest Asks to Extend Fish Farm, 6 April 2018.
  4. Scottish Government, Aquaculture, 17 June 2019.
  5. The Herald, One fish farm produces waste equivalent to ‘all of Scotland’s west coast towns’ 15 March 2018.
  6. BBC News, Scotland’s wild salmon stocks ‘at lowest ever level’, 24 April 2019.
  7. The Guardian, Salmon farming in crisis: ‘We are seeing a chemical arms race in the seas’, 1 April 2017.
  8. The Herald, Revealed: Scandal of 45 Scottish Lochs Trashed by Pollution, 26 February 2017.
  9. BBC News, Scottish Salmon farming ‘risk’ to wild wrasse, 21 June 2017.
  10. BBC News, Sark moves to ban exports of wrasse as salmon’s cleaner fish, 12 April 2019.
  11., How much wild fish is there in fish farming feed?, 2018.
  12. The Ferret, Horror photos of farmed salmon spark legal threat, 27 June, 2018.
  13. BBC News, Half the fish at Wester Ross salmon farm wiped out, 15 December 2018.
  14. BBC News, MSPs warning over salmon farming impact on environment, 5 March 2018.
  15. BBC News, Stricter rules could close salmon farms, 7 November 2018.
  16. The Guardian, Heritage body objects to plans for big salmon farm off Hebridean isle, 19 Aug 2019.
  17. The Sunday Post, Hundreds create human chain on Isle of Arran to protest proposed new fish farm, 17 September 2019.
  18. The Herald, Citizen Science Activists Target Salmon Farms, 28 August 2019.
  19. The Guardian, Scottish salmon farmers to be banned from shooting seals, 17 June 2020.
  20. The Independent, UK supermarkets selling ‘sustainable’ Scottish salmon linked to collapse of wild fish stocks, 15 October 2019.
  21. i Newspaper, Seafood sustainability: Aldi and Iceland come bottom of supermarket rankings, 19 March 2020.
  22. BBC News, Why is there a row over seaweed harvesting in Scotland?, 21 November 2018.
  23. BBC News, How lasers and robo-feeders are transforming fish farming, 20 February 2018.
  24. The Scotsman, Could the Humble Sea Cucumber Clean up Scotland’s Fish Farms?, 4 February 2021.
  25. Undercurrent News, European Industry Targets Doubling of Aquaculture Production by 2030, 5 December 2018.
  26. Changing Markets Foundation, Dead Loss: The High Cost of Poor Salmon Farming Practices, February 2021.

Please note: This article was originally about fish farming in general. It was rewritten in March 2020 to focus specifically on the issues affecting the Scottish fish farming industry. Changes and developments which have taken place since this date will not be reflected in this article.