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Establish a code of practice for farmed fish in the UK (trout and salmon)

Updated: Jul 19, 2022


Whilst working with Animal Equality UK on their Ask Prioritisation, we saw an avenue for further exploration and prioritisation of asks within the wider UK context. We want our research to be as useful to as many groups as possible and as such, decided to run a simultaneous research process for the full UK context outside of the limitations of Animal Equality UK’s scope. We contacted all major animal advocacy organisations in this region and they were keen to understand the results of this UK-wide scoping following our research. We would like to thank the experts we looked to for guidance in this report. We recommend that any organisations wishing to work on this issue to get in touch with both ourselves and with Advocates for Animals, a UK-based law firm who have extensive knowledge on this matter.


This is a summary research report by Animal Ask on behalf of UK animal advocacy organisations, investigating whether establishing a welfare-based Code of Practice for Scottish salmon could be a recommended intervention for improving the welfare of salmon in the UK.

The lack of an official Code of Practice for farmed fish in the UK is a glaring omission: they are one of the few farmed animals in the UK that does not have one. The implementation of an official Code of Practice is especially important given their high population and the extreme neglect of their welfare by present unofficial industry standards. They suffer from a host of welfare issues, of which the most significant are sea lice, sea lice treatments, cleaner fish welfare, and slaughter. It appears clear that the industry is failing to regulate itself.

Moreover, there appears to be fertile ground for work on the subject since there is an ongoing review of the regulation of the Scottish aquaculture industry, pushed by the Scottish Green Party who have goals to more radically reform the industry. Though so far the discussion of the review has centred around impact on humans and the environment, politicians could be receptive to the inclusion of animal welfare in the reconstruction of industry regulation.

Despite these points in favour, there are also some considerations against working on this ask. These include that virtually all salmon farms are currently signed up to the Code of Good Practice - which, though vague and inadequate, does offer some minimal protection - while 70% of farms are signed up to RSPCA standards. For an official code to be most impactful, it would have to exceed these standards. While there is room to do so, even for the higher RSPCA standards, it may be difficult to get a code with higher standards passed. Nevertheless, a new Code of Practice could still be impactful if it covered for specific weaknesses in these unofficial codes, if it increased enforcement of these regulations, or if it served as a first step to enable stronger legislative tasks in the future.

Overall, we consider this a strong ask and recommend it to UK organisations. To be most effective, work must be started before the review is completed.


This intervention would see a campaign directed at the Scottish government to provide a coherent regulatory framework for salmon aquaculture. This would challenge the de facto use of the industry Code of Good Practice for guidance. A successful campaign would encourage the Scottish Government to either adopt the industry code as official guidance or draft a new code.


The Scottish salmon industry raised 51.4 million smolts (juvenile salmon) in 2019 (Scottish Government 2019). The country is the third-largest producer of salmon in the world, behind Norway and Chile, and produced £765 million of salmon by value in 2016 (Kenyon and Davies 2018).


Regulation of aquaculture in Scotland is split across several different bodies, each with their own focus. The Fish Health Inspectorate (FHI), an agency of Marine Scotland Science, is responsible for ensuring fish health, such as by inspecting salmon farms to evaluate sea lice burdens, mortality rates, and disease (“Fish Health Inspectorate” 2014). Another body, the Scottish Environmental Protection Agency (SEPA) is responsible for monitoring and assessing the environmental impact of the farms.

From a fish welfare perspective, the FHI is the most relevant body. They use a risk-based approach to monitoring, meaning that sites with higher risk are inspected more frequently. Inspections range from once a year to at least once every three years (Kenyon and Davies 2018). The majority of the FHI’s work is carried out under the following legislation (FHI n.d.):

The FHI does not appear to devote resources to monitoring fish welfare, except where matters of fish health overlap with welfare. Indeed, OneKind (a Scottish animal welfare charity) told us that if FHI sees a welfare violation they report it to the Animal and Plant Health Agency (APHA).

The Aquaculture and Fisheries (Scotland) Act 2007 provides Scottish minsters the power for the approval of official Codes of Practice for fish or shellfish farming. In a 2013 amendment, a reference to the “Code of Good Practice for Scottish Finfish Aquaculture” was included in one section. This particular Code is subscribed to by the Scottish Salmon Producers’ Organisation and the British Trout Association (Code of Good Practice n.d.). However, the Code is not official which significantly weakens the potential for strong welfare protections for fish².


The Code of Good Practice for Scottish Finfish Aquaculture (‘CoGP’ from now on) is subscribed to by the Scottish Salmon Producers’ Organisation (SSPO) and the British Trout Association. According to its website, the SSPO represents all Scottish salmon producers, as well as a number of smolt (juvenile salmon) producers (SSPO n.d.). All producers in the SSPO subscribe to the Code except for Grieg Seafood Shetland Ltd., meaning that in 2018 90% of production was covered by the Code (OneKind 2018b)³. Recently, Grieg Seafoods farms have been bought out by Scottish Sea Farms (Munro 2021) so the CoGP should cover all salmon going forward. The CoGP covers many aspects of the farming of salmon from breeding through to processing.

It is worth noting that around 70% of Scottish salmon are certified to the RSPCA Farm Assured Scheme (SSPO n.d.). The RSPCA standards include many requirements on welfare-related issues, including stocking density, handling, and slaughter (RSPCA 2021). A small number of farms are also certified under Soil Association Organic standards.


The argument for the campaign is that, as provided by the Aquaculture and Fisheries (Scotland) Act 2007, the Scottish Government has the power to create an official Code of Practice for the salmon industry. This would clarify how Scottish animal welfare law should be complied with by the industry. However, the Scottish Government has not chosen to create an official Code of Practice, other than a short Code dealing only with marine mammal interactions. The case for the campaign would be that this amounts to self-regulation by the industry, which should not be expected to ensure necessary welfare outcomes, and indeed has not.

An official Code of Practice works to explain how the industry can comply with the law. For example, the Code of Practice for the Welfare of Pigs advises how pig farmers can comply with legislation - principally the ‘Welfare of Farmed Animals (England) Regulations 2007’ and the ‘Mutilations (Permitted Procedures) (England) Regulations 2007’ in that particular case the current situation for Scottish salmon is that, unlike for other farmed animals, there is no official code concerning their welfare. This means that vague legislative protections create ambiguity and the industry is unaware what it has to do to comply with the law. It may also lead people to treat the codes as voluntary rather than as binding regulations. This may lead producers to be lax in their compliance with the industry code, something that undercover footage has indicated is the case (Animal Equality 2021).



In this section, we will break down the main welfare issues faced by Scottish salmon (and cleaner fish) and assess both their magnitude (how many fish are affected) and severity (how severely welfare is impacted). This is intended to give a sense of the current state of fish welfare in the industry and where there is the biggest room for improvement. In addition, we highlight relevant passages from the industry’s CoGP which address (or partially address) these welfare issues. We have noted where the CoGP is vague or lacking in guidance on certain welfare issues in order to highlight its significant weaknesses.

For a comprehensive review of the welfare issues facing farmed salmon in Scotland, it is worth reading the report by OneKind. Additionally, a recent report from Compassion in World Farming provides further information and evidence on welfare. OneKind has also produced a report on the welfare of cleaner fish.


1.1. Welfare

Sea lice are parasites that feed on the skin, scales, tissues, and mucous layer of salmon. This reduces the host's appetite and growth, increases stress (Bowers et al. 2000; Ross et al. 2000), and causes external wounds. All of these factors reduce the vitality of the salmon, making them more vulnerable to infections and disease (Abolofia, Asche, and Wilen 2017). Therefore, although sea lice themselves are unlikely to directly cause the death of the fish, they compromise its immune function, potentially indirectly leading to its death. The more severe the sea lice infestation, the greater the compromise in the function and welfare of the host - ultimately leading to higher mortality rates (Vollset 2019; Morton 2005). These consequences can be sufficiently extreme that moderate to severe sea lice infestations would probably factor as the dominant cause of suffering in those salmon afflicted and sufficient to make their lives not worth living.

Reporting shows that sea lice levels on Scottish farms are often high. A report by OneKind in 2017 found that sea lice trigger levels (an average of 3 female lice per salmon at the time the report was published) were breached on more than 500 occasions in that year (OneKind 2017). Between 2018 and 2019, the Scottish Salmon Producers Organisation’s (SSPO) monthly averages suggest that the average adult female sea lice count per fish increased by 96% (CIWF and OneKind 2021). However, in 2020 the SSPO reported that the number of sea lice affecting farmed salmon was at its lowest level in seven years (RSPCA n.d.). Figures from September 2020 show that out of 211 seawater sites in Scotland (with 59 lying fallow), 23 of them experienced a sea lice problem that required treatment (either 1 or 0.5 female lice per fish, depending on the time of year). This is 15% of farms (RSPCA n.d.). Overall, year to year there seems to be huge fluctuations in the number of sea lice.

1.2. Industry CoGP

Relevant points from the current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • It is a legal requirement to maintain specific records in relation to sea lice. The record-keeping requirement set out in law is based upon the provisions of this CoGP.

  • A protocol is set out for counting sea lice numbers.

  • A threshold is set for when treatment of sea lice should occur (average of 0.5 or 1 adult female louse per fish, depending on the time of year).

Sea lice reporting and management is a topic that is addressed through specific legislation. Current legislation requires weekly reporting of sea lice levels. If reported counts rise above an average of two female lice per fish, FHI will increase monitoring. If levels either increase above six lice per fish or remain above two lice per fish, enforcement notices can be issued (Marine Scotland 2021).

Legislation on sea lice reporting and enforcement (Marine Scotland 2021)

The industry CoGP suffers from a number of failings. It does not require the extent of sea lice damage to salmon to be recorded during sea lice counts. There is no requirement for fish with severe physical damage caused by sea lice grazing to be removed immediately and killed humanely. It fails to discuss the impacts of sea lice on wild salmon and it only considers adult female sea lice, even though other life stages have been found to affect welfare (CIWF and OneKind 2021).

1.3. Summary

Scale: Medium. The majority of farms do not suffer from serious sea lice problems. However, statistics show that the issue is still common, with 15% of farms requiring treatment in a single year.

Severity: High. Sea lice infestations are a severe welfare problem for affected salmon.

Strength of current CoGP guidance: Weak. The welfare impacts of sea lice on salmon could be made a much higher priority within the CoGP.


2.1. Welfare

To remove sea lice from salmon, farms use a few different treatments that can compromise welfare. While cleaner fish are also commonly used, these will be covered in a different section. One common method of sea lice removal is the thermolicer, a heat-based treatment. This machine pumps salmon through a system that exposes them to 30-34C water, removing the lice. The process lasts about 30 seconds before the salmon are pumped back into their pens (SSPO n.d.). Other than the thermolicer, other treatments include the Optilicer (thermal) and Hydrolicer (mechanical). From information reported by Scottish farms about sea lice and the treatments used, we can establish that between 29/03/2021 and the date of writing this (28/05/2021), 34 mitigation measures were put in place to deal with sea lice. Of these, nine involved the use of a physical treatment (usually reported as the hydrolicer, although it is not clear if some of these were also thermolicers). This implies that roughly a quarter of responses to sea lice involve physical/thermal treatments. The rest of the measures were reported as bath only (6), bath and harvesting (3), cleaner fish only (6), cleaner fish and harvesting (3), or harvesting only (7) (FHI 2021).

An average of 44,400 salmon per year were recorded as killed by thermolicers in Scotland between 2016 and 2019 (Edwards 2020). Welfare issues associated with this treatment include crowding, pumping, fish taken out of water, pain caused by the warm water, fish with compromised health (such as gill disease) being subjected to severe harm or death, and possible immunosuppression caused by handling (CIWF, n.d.).

Other treatments for sea lice also have negative effects on welfare, which we will not fully detail here. For a more comprehensive overview of the welfare impacts of different treatments, refer to this report by Compassion in World Farming.

2.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • “Treatment for episodic C. elongatus [a type of sea louse] infestations should be applied, as appropriate, to protect the welfare of farmed salmon.”

  • “Treatments should be carried out promptly to maximise the effectiveness of the available medicines, promote the minimal use of medicines consistent with the maintenance of high standards of fish welfare and help preserve efficacy.”

These provisions for protecting the welfare of the salmon in the CoGP are minimal and do not make any reference to the welfare impacts of the treatments themselves. There is no requirement to perform a welfare assessment before new treatments for sea lice are approved. In addition, it is not required to perform a risk assessment of welfare prior to treatment in order to prevent salmon with very poor health from being exposed to further stressors. OneKind has called for these protocols previously (OneKind 2018b).

2.3. Summary

Scale: Medium. Several million salmon each year are treated for sea lice.

Severity: Medium. Treatments for sea lice have some welfare benefits as they reduce sea lice loads on salmon. However, many of the treatments used have a clear negative impact on the welfare of the salmon, sometimes causing acute suffering and/or death.

Strength of current CoGP guidance: Very weak. No guidance is provided on how to select treatments that compromise welfare the least. There are no requirements to properly consider welfare before starting treatment.


3.1. Welfare

Cleaner fish are used as an alternative to chemical and mechanical treatments for sea lice. They are introduced into pens because they are able to eat sea lice off the salmon. Lumpsuckers and wrasse are the two species that are most typically used.

In 2016, the salmon farming industry used approximately 1.5 million farmed cleaner fish (although it is likely that many fish harvested from the wild were also used) (Scottish Government 2017). One paper has estimated that 10 million cleaner fish would be used in the UK by 2020, although it is unclear how the authors arrived at this estimate or whether the estimate has turned out to be correct (Powell et al. 2018). There is likely to be an increasing shift towards the use of hatchery-raised cleaner fish, both to protect wild fish stocks and supply the growing demand for cleaner fish.

A report by OneKind covers the welfare issues facing cleaner fish in detail (OneKind 2018a). Official data on cleaner fish mortalities is not available in Scotland. However, figures from the Norwegian salmon farming industry show that mortality is a serious issue. One study found that 57% of wrasse and 27% of lumpfish died in a four-month period (Geitung et al. 2020). Another report states that losses of cleaner fish in Norway run at about 40% (Eurogroup for Animals 2020).

There is evidence that wrasse can sometimes be aggressive towards salmon, causing damage to eyes and even death. Salmon also sometimes prey on cleaner fish, while some cleaner fish may engage in cannibalism. This is exacerbated by a lack of cover to pens to shelter the fish, particularly for wrasse who would naturally live undercover on the seafloor. It is also likely that the living conditions in salmon pens are unsuitable for cleaner fish (Borthwick 2020).

3.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • The use of hatchery-reared cleaner fish is prioritised over wild-caught.

  • A risk assessment should be performed before the introduction of cleaner fish, as well as a health check for diseases.

  • Cleaner fish should either be ‘humanely destroyed’ or ‘reused’ no more than once.

  • Each pen should have adequate provision of hides for cleaner fish.

  • Supplementary food should be made available for cleaner fish.

  • Each farm using cleaner fish should have appropriately trained staff, taking into consideration husbandry, health and welfare.

Whilst it is positive that the CoGP acknowledges some of the welfare requirements of cleaner fish, the small section devoted to their welfare is obviously inadequate to properly care for these fish. Furthermore, all provisions concerning cleaner fish come under the heading “Biological Vectors of Fish Disease” in the CoGP, indicating that their welfare is a secondary concern to that of the salmon they are cohabiting with.

More detailed guidance on the number and type of hides to provide would be valuable, as well as the provision of substrates. Furthermore, good transport and handling practices should be addressed, as well as appropriate limits set for stocking density. More detail on what constitutes ‘humane’ slaughter is also important. Proper protections for the welfare of cleaner fish before they are introduced into salmon pens are also important, given that welfare standards should cover the wild capture/hatchery stages of cleaner fish life cycles.

The RSPCA standard for Atlantic salmon, which around 70% of farms adhere to, goes significantly further than the CoGP and includes 10 pages of requirements for cleaner fish welfare (RSPCA 2021). However, OneKind points out that there are no standalone, species-specific welfare standards for cleaner fish used on Scottish salmon farms. They believe that more detailed guidelines are needed, such as those provided by the Norwegian Seafood Research Fund in Norway (OneKind 2018a).

3.3. Summary

Scale: Medium. Up to 10 million cleaner fish are used each year in Scotland.

Severity: High. The high mortality rates alone are sufficient evidence that cleaner fish welfare is greatly compromised by their use in aquaculture.

Strength of current CoGP guidance: Weak. A couple of important provisions are made for cleaner fish. However, guidance is very brief and does not cover many aspects of the cleaner fish life cycle. It also gives the impression of a side note rather than an acknowledgement of the importance of cleaner fish welfare.


4.1. Welfare

Escapes from fish farms can have negative consequences for the farmed fish that escape and also any wild fish that they interact with. In 2020, more than 130,000 fish were reported to have escaped from Scottish salmon farms. In 2019 this was around 30,000, while in 2018 it was around 40,000 (Natural Scotland 2021). Holes in nets, bad weather, and handling before delousing operations are some of the most common reasons for escapes (Føre and Thorvaldsen 2021).

There has been little research done into the effects of escape on the welfare of the fish who swim free. Escaped fish may benefit from being free of the constraints of their pen and the high stocking densities, diseases and sea lice generally associated with farmed life. However, since they are not adapted for the wild and have lived their whole lives in captivity, escaped fish may struggle to find food and end up suffering anyway.

Another concern is how the escaped salmon interact with the wild salmon population in Scotland. Fewer than half a million wild salmon are estimated to remain in Scotland and their population has been declining for decades (K. Ashley 2019). Farmed salmon escapes compromise the welfare of wild salmon since they can interbreed, resulting in offspring that have reduced fitness and are less likely to survive. It has also been suggested that escaped farmed salmon compete with wild salmon for food (OneKind 2018b).

4.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • Nets should be checked often for damage and holes. Remedial action should be taken immediately to rectify any problems.

  • Farmers should have evidence that the pens are installed correctly and are inspected and approved by qualified staff.

  • Nets should be tested at a predetermined frequency.

  • A certain minimum net strength is required.

  • The risk of escapes during harvesting should be assessed and mitigated.

  • “Farmers should have site-specific contingency plans that describe actions to be taken in the event of any escapes.”

  • Daily visual inspection of the holding units should be carried out to ensure containment.

  • Any escape, or suspected escape, of live fish should be reported immediately (or at the latest, within 48 hours of discovery) to all relevant stakeholders.

  • “A decision to attempt to recapture fish and the method to be employed should be agreed with the local District Salmon Fisheries Board and Fisheries Trust and permission sought from Marine Scotland.”

The CoGP provides better guidance on preventing and dealing with escapes than it does on many other issues.

4.3. The official Code of Practice

The official Code of Practice covers escapes, but mainly in the context of escapes caused by interactions with marine mammals (The Scottish Government 2021). This can happen when seals tear at the nets in order to get at the fish inside. While this will likely be helpful for those cases, this is not one of the main causes of fish escapes, and so this Code of Practice is inadequate overall on the subject of fish escapes.

4.3. Summary

Scale: Small. A few tens of thousands to hundreds of thousands of fish escape each year. Some wild salmon are also affected when interbreeding occurs.

Severity: Low. It is hard to know the welfare impacts that escapes have on the fish involved. It is plausible that the fish experience some benefits of escape, although we expect that the overall welfare impact is more likely to be negative given these fish will probably be replaced with additional farmed fish.

Strength of current CoGP guidance: Moderate. Reasonable guidance is given on preventing escapes, not too dissimilar from the RSPCA’s standards.

Strength of current official Code of Practice: This only covers escapes caused by marine mammals, which is not one of the primary causes of fish escape.


5.1. Welfare

One solution proposed to reduce the impact of escaped farmed salmon on wild populations is to use triploid fish. These are fish that have an extra set of chromosomes, achieved by applying a heat or pressure shock on newly fertilised eggs. This means triploid fish are sterile and so cannot interbreed with the wild population. However, triploid salmon have been shown to have reduced welfare compared to normal diploid salmon. One study found that triploid salmon have an increased prevalence of spinal deformities (between 2-3% are deformed, compared to 0-1% of diploid salmon) (Fjelldal and Hansen 2010). Triploids are also more vulnerable to temperature stress, though they may also be less aggressive (Fraser et al. 2012). They can also have a higher mortality rate than diploids (Cotter et al. 2002; Benfey 2001). Therefore, even if it may serve to protect wild populations, it is important for overall welfare that triploid fish are not used in salmon farming.

5.2. Industry CoGP

The current industry CoGP does not mention triploid fish, so if this was made official some improvement would have to occur for it to have an effect on this practice. The RSPCA are currently monitoring the work being done on triploid salmon and will use this information to determine whether triploids will be able to be used in the future under their standards.

The RSPCA standards include this note on triploids:

“At present the RSPCA welfare standards for farmed Atlantic salmon only apply to diploid fish. The RSPCA is monitoring the work being done on the specific needs of triploid salmon, such as diet, management and health care, in order to investigate how and whether their welfare needs can be properly satisfied, which will ultimately determine whether they will be allowed to be used in future under the standards.”

An improved CoP should preferably ban the use of triploids, or at least set certain standards for the use of triploids if they are ever used by the industry in future. OneKind supports a ban on the use of triploid salmon (OneKind 2018b).

5.3. Summary

Scale: Unclear. Our assumption is that triploid salmon are not currently used in Scotland (since the RSPCA currently do not allow it, and we haven’t found any reports suggesting they are used). It is difficult to know whether they will ever be used by the industry in the future and, if so, the scale of that use.

Severity: Medium. The use of triploids may slightly benefit the wild population of salmon. However, this will likely be far outweighed by the increased deformities and mortality experienced by triploid salmon.

Strength of current CoGP guidance: No guidance exists. The current Code does not mention the use of triploid fish.


6.1. Welfare

The stocking density of pens (usually measured in kg of fish per m3 of water) is one of the most important factors in the welfare of farmed fish. The interaction between stocking density and welfare is a complex one since stocking density can have knock-on effects on other parameters, such as water quality and spread of disease. One study examined welfare indicators in Atlantic salmon in cages on a commercial marine farm, at densities ranging from 9.7 to 34 kg/m3. The authors found that stocking density did not affect welfare up to an inflection point of 22 kg/m3, at which point welfare then began to deteriorate (Turnbull et al. 2005). Another study examined salmon welfare at 15, 25, and 35 kg/m3. This study found that welfare was best at 25 kg/m3, suggesting that welfare can also be compromised at lower densities (Adams et al. 2007).

6.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • “As a general rule, stocking density may be adjusted in line with the biological and behavioural needs of fish having regard to the prevailing environmental conditions and, in particular, water quality. The farming system in which the fish are held and the ability to maintain high standards of water quality are important defining factors in determining optimum stocking density.”

  • “Stocking density should be monitored in relation to fish health, fish behaviour and water quality to ensure that fish welfare is not compromised.”

  • “The size and proportions of pens should be sufficient to allow the fish to behave in a manner that is conducive to high standards of welfare.”

These guidelines provide general advice to maintain a stocking density that does not compromise fish welfare. However, the CoGP does not advise on a specific maximum density, even though the scientific literature gives a good indication of what this might be. The RSPCA standards require a maximum of 15-17 kg/m3 for adult salmon and provide important guidance on how stocking density should be calculated. The RSPCA standards also give specific maximum stocking densities for salmon in hatchery and juvenile stages of the life cycle (RSPCA 2021).

6.3. Summary

Scale: Low. All ~50 million Scottish salmon per year are affected by stocking density. However most if not all Scottish farms are likely to be stocked below 22 kg/m3.

Severity: High. Stocking density is a very important aspect of salmon welfare.

Strength of current CoGP guidance: Weak. Only general statements about stocking density and welfare are made. No specific maximum limits are given.


7.1. Welfare

Water quality variables in aquaculture have been defined as “any characteristic of water that affects the survival, reproduction, growth, production, or management of fish” (Boyd and Pillai 1985). This includes dissolved oxygen, carbon dioxide, ammonia, nitrite, nitrate, pH, turbidity, salinity, hardness, and temperature. While each of these parameters has some importance for the welfare of the fish, dissolved oxygen is generally considered the most important. A more in-depth review of the importance of overall water quality can be found in our previous report, which we produced for Sinergia Animal on fish welfare in Southeast Asia (to be published), and Charity Entrepreneurship’s report on environmental conditions for fish (Sarek 2019).

To summarise our previous findings, poor water quality can have a large impact on the welfare of fish. If it is not managed carefully it can cause stress, poor appetite, slow growth, disease susceptibility, and mortality. The optimal level of each water quality parameter for the welfare of fish depends on the species. Fortunately, the RSPCA welfare standards provide acceptable ranges for different life stages specific to salmon:

One important note to make in this context is that most finfish aquaculture in the UK is in sea cages where the water quality is largely dependent on the surrounding area and the flow rate through the cage. Some issues can block or reduce proper exchange, such as biofouling (Gansel, McClimans, and Myrhaug 2010) or when the cages are arranged closer together in a suboptimal pattern. There have been attempts to directly improve the quality of the water in cages, most notably with dissolved oxygen (Berillis et al. 2016). However, water quality is generally less of a problem in cages, though also much more difficult to control. It is easier to control the water during the freshwater stages of development if tanks, ponds, or raceways are used.

7.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • “The siting of farms should be such that there is an adequate supply of water of suitable quality at all times.”

  • “Where appropriate, there should be emergency back-up systems to maintain a high standard of water quality.”

  • “Sites should be located and operated in such a way as to minimise the possibility of adverse environmental conditions having an undesired effect on the fish.”

  • “Farmers should have written contingency plans covering actions to be taken in the event of a serious incident, such as storm damage or water quality problems. These plans should consider both the welfare of the fish and environmental protection.”

The CoGP provides little guidance on practical steps or requirements for maintaining water quality. All of the terminology is quite vague, leaving it largely up to the farmer as to what constitutes ‘suitable quality’. This could be easily improved by integrating the RSPCA’s standards for water quality, as well as possibly providing additional advice on what actions to take to improve different parameters in different systems.

7.3. Summary

Scale: Medium. All ~50 million Scottish salmon per year are affected by water quality during all stages of their lives. The current state of water quality on Scottish salmon farms is unclear.

Severity: High. Water quality is one of the most important aspects of finfish welfare.

Strength of current CoGP guidance: Weak. Guidance is very vague, leaving interpretation largely up to the farmer.


8.1. Welfare

The barren interior of salmon pens differs from the natural environment that wild salmon would be living in. Provision of structures and objects that attempt to create an environment on a farm that more closely mirrors the challenges and variety experienced by wild animals is often known as ‘environmental enrichment’.

Current research on the impact of enrichment on salmon welfare, and which kinds of enrichment are best, is still limited. One study found that the provision of shelter (shredded material) decreased aggression between salmon smolts, as well as levels of stress hormones following disturbance. However, the same study found that the provision of shelter reduced the growth rate of fish at high densities (Rosengren et al. 2017). Another study used shredded plastic bags and plastic tubes as enrichment for juvenile salmon and found that in the barren tanks, fish showed higher cortisol levels and more fin damage than fish reared in the enriched environment (Näslund et al. 2013). However, the current lack of literature means that more research is needed to determine how enrichment could be best used to improve farmed salmon welfare.

8.2. Industry CoGP

No mention of environmental enrichment for salmon was found in the current industry CoGP.

Currently, the limited evidence makes it difficult to recommend particular enrichments with a high degree of confidence. However, the importance of enrichment should be firmly emphasised, and farms should be striving to identify and provide appropriate enrichment for their salmon. OneKind calls for the provision of enrichment to reduce stress and aggression levels, and suggests that this could include structures that mimic seaweed or shelters (OneKind 2018b). The RSPCA standards do not specify any enrichment guidelines for salmon but do note the following:

“The RSPCA are aware of trials examining the introduction of environmental enrichment to tanks to reduce fin damage. The results from such trials would be greatly appreciated by the RSPCA Farm Animals Department in order to inform future standards.”

8.3. Summary

Scale: Large. All ~50 million Scottish salmon per year could potentially benefit from environmental enrichment.

Severity: Unclear. Further research needs to be conducted to fully understand the extent of the benefits of enrichment for salmon.

Strength of current CoGP guidance: No guidance exists. The Code does not mention environmental enrichment for salmon.


9.1. Welfare

Handling and transport can be two of the most acutely stressful events for farmed fish. There is significant evidence that handling, crowding, and grading cause stress responses in fish (P. J. Ashley 2006). As well as causing high levels of stress, handling can also result in physical damage, such as the removal of scales. Handling of farmed salmon occurs at multiple different stages in their lives, including during vaccination, grading (a process to separate fish into groups according to their size), disease/lice treatment, and transport.

9.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):


  • Live fish should only be removed from water and handled when absolutely necessary.

  • If fish are handled, adequate support should be given to the body - live fish should never be held by the gills or tail only.

  • Different species have different tolerance to being out of water, but the time out of water should never be so long as to produce signs of distress.

  • In all cases, fish should be kept wet, except where blotting dry is essential to avoid contamination of gametes during stripping.


  • A written procedure for crowding of fish should be prepared.

  • The frequency and duration of crowding should be kept to the minimum.

  • Farmers should monitor fish behaviour during crowding and take action if fish show signs of stress or damage.

  • Farmers should remove and cull any moribund or damaged fish.

  • Farmers should ensure that enclosure nets and screens are kept clean in order to avoid water quality problems during crowding.

  • Farmers should monitor oxygen levels during crowding and take corrective action if levels fall below a critical point for that species.


  • The avoidance of injury and stress to fish should be a primary consideration when deciding on the method of grading to be employed.

  • Grading equipment should be designed and maintained so as not to damage the fish.


  • Crowding of fish before collection for transport should be kept to a minimum.

  • Fish should be transported in such a way that possible adverse effects on their welfare are minimised.

  • Biosecurity and fish welfare should be considered before transporting fish populations.

  • For transport, oxygen monitoring should be carried out with sufficiently frequent monitoring intervals to ensure that oxygen levels remain within safe limits at all times.

  • Supplementary oxygen or air supply should be sufficient to last longer than the anticipated length of the journey, including helicopter transport.

  • Excessive or rapid changes in water temperature or pH in transport tanks should be avoided.

  • Any fish that die during transportation should be separated from live fish as soon as possible after arrival and the cause of death determined by a competent person.

It is positive that the CoGP frequently refers to the welfare of fish in these sections. However, the guidance is generally very weak. For example, although crowding should be kept to a ‘minimum’, no specific time durations are given as limits. Fish must also not be kept out of water ‘so long as to produce signs of distress’, but again no time limit is given. Stronger guidance providing these limits would mean that farmers could be held accountable. Standards from the RSPCA could be adopted to achieve this. For example, RSPCA standards require that fish must not be crowded for more than two hours and that a conscious fish must not be out of water for more than 15 seconds (RSPCA 2021).

9.3. Summary

Scale: Large. All ~50 million Scottish salmon each year are affected by handling and transport processes.

Severity: Moderate. Handling and transport can cause severe acute stress that may take several days to recover from (and could also have long-term effects). However, the suffering caused by these procedures is probably of shorter duration than some other welfare issues in salmon farming, such as sea lice or stocking density.

Strength of current CoGP guidance: Weak. The Code provides very general welfare guidance on protecting fish welfare and is severely weakened by the lack of concrete limits.


10.1. Welfare

95% of salmon in Scotland are slaughtered using percussive stunning followed by bleeding, which is thought to be the most humane method. The remaining 5% are killed using electrical stunning before bleeding (SSPO n.d.).

In order to minimise suffering, a stun should be instantaneous and unconsciousness should remain until death (i.e. the fish must not become conscious while it is bleeding out). The use of a stunning machine in a facility is therefore not enough on its own to guarantee that welfare is protected. For suffering to be minimised, the stunning and killing process must be closely monitored to ensure that unconsciousness is maintained throughout and that appropriate steps are taken in any instance where a fish is seen to be conscious.

Concerningly, a recent Animal Equality investigation of a slaughter facility operated by The Scottish Salmon Company (Animal Equality 2021) found that many salmon experienced highly stressful and painful deaths despite the use of stunning machines.

This problem has been observed in other fish species where lab-proven humane slaughter methods are difficult to implement in practice. A study on the pre-slaughter stunning of common carp in German slaughterhouses illustrates how prevalent unsuccessful stunning can be. The study found that across the three slaughterhouses that were monitored, percussive stunning resulted in 46.2% of fish displaying behavioural indicators of consciousness at the time of slaughter (Retter et al. 2018). Caution is required in considering these findings in the Scottish salmon context. Practices may differ between Scotland and Germany, while separate studies on the efficacy of percussive studies for carp and salmon indicate carp may be more difficult to stun than salmon (Lambooija et al. 2010; Robb et al. 2000; Lambooij et al. 2007). However, it demonstrates the importance of identifying the optimal parameters for stunning machines, as well as effectively monitoring fish for signs of consciousness.

10.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • Fish should be fasted for the minimum period necessary to clear the gut of feed and faeces.

  • Crowding fish prior to harvesting should be for the minimum time possible, especially where more than one crowding session is necessary to complete the harvest.

  • Killing efficiency should be monitored by a proficient person to ensure fish do not regain consciousness prior to death.

These guidelines are clearly very minimal and do not provide important details about how fish should be checked for consciousness. Furthermore, no information is given about what backup killing procedures should be performed in case a fish is found to be conscious. The weakness of this guidance is clear when it is contrasted with the detailed guidelines for ensuring proper stunning provided in the RSPCA standard:

Before the beginning of each harvest:

a) the stunning system must be tested to ensure it is working properly

b) the first 10 fish through each stunner must be assessed and demonstrate the following to ensure the system is functioning correctly:

i) the checks must include that fish have no eye movement

ii) no rhythmic opercular movement

iii) only mild short term involuntary muscular twitches

iv) no reaction to tail pinch

c) the results of the checks listed in a) and b), above, must be:

i) recorded, and

ii) made available on request.

The industry CoGP lacks, among other things:

  • A specific time limit on fasting length,

  • Detailed guidance on the procedures and machine parameters needed to produce effective stunning,

  • Detailed guidance on the monitoring of fish consciousness during slaughter,

  • A requirement to record the number of unsuccessful stuns and fish regaining consciousness,

  • A requirement for contingency plans to be made to humanely deal with unsuccessfully stunned fish,

  • Detailed guidance on the humane slaughter of cleaner fish,

  • And a specified maximum length of time between the stunning and bleeding of fish.

10.3. Summary

Scale: Medium It is difficult to establish what percentage of Scottish salmon currently suffer unnecessarily at slaughter. However, all of the industry uses a stun before slaughter.

Severity: Moderate. Slaughter while conscious causes severe acute pain and stress. Poor harvesting procedures may also cause short-term stress. In comparison to some other welfare issues, the duration of potential suffering caused by harvesting and slaughter is relatively short.

Strength of current CoGP guidance: Very weak. The Code provides extremely minimal guidance on how to perform these technically complicated procedures without compromising welfare.


11.1. Welfare

Salmon are carnivorous. The composition of their diet varies throughout their life stages, with younger freshwater salmon eating more insects while adult salmon subsist on other marine animals. In aquaculture, salmon feed is carefully formulated for each life stage by varying protein, lipid, and nutrient content (“FAO: Feed Production” n.d.). This provides the salmon with the nutrients they need to grow and develop into the next stage. The ingredient composition used to achieve these goals has changed in recent decades. One recent study has produced estimates of the ingredients used in salmon feed in Norway (Aas, Ytrestøyl, and Åsgård 2019). In the figure below you can see the general trend, with the percentage of marine oil and protein sources reducing dramatically over the past 30 years. Although this data is from Norwegian salmon farms we expect this to generalise to the Scottish context.

Ingredient sources (% of feed) in Norwegian salmon feed in 2016

The main benefit of this reduction in the use of marine ingredients in salmon feed is the lower demand for other, mostly wild-caught, fish. The most straightforward benefit this has to wild fish is sparing them the experience of capture and slaughter. As there are no protections for wild-caught fish, this is usually a very stressful process culminating in death by asphyxiation - a process that can take more than 30 minutes for some species. This is likely to be one of the worst ways to die as a fish. However, it is important to consider the counterfactual cause of death for the fish if they had not been caught. They could die of starvation, disease, or predation, all of which are unpleasant ways to die. Beyond this effect, there are additional considerations about the effect of fishing on wild populations. If the industry is overfishing, reducing demand for wild-caught fish could increase wild fish populations. The quality of a wild fish’s life, as well as the effect of this population change on the rest of the food chain, could dramatically change the positive or negative direction of this effect, without even considering any other ethical considerations beyond utilitarianism. This means that modelling the benefit of reducing marine ingredient use to wild fish populations is complicated and something we can’t achieve in the short review here.

The effect of reducing the percentage of marine ingredients on the welfare of salmon themselves is neutral or slightly negative. If managed properly, the growth of the salmon will be unaffected. However, if too little is used this could be detrimental for productivity, and more importantly the health and welfare of the fish. Some compositions can cause differences in growth rates even at higher percentages of fish meal. Bransden et al. (2001) compared the effect of replacing some of the fishmeal in their diet with dehulled lupin meal (LPN), hydrolysed poultry feather meal (FTH), or a mix of both for salmon. All feed mixes had fishmeal contents above 30%. They found that the highest weight gain was achieved on the mixed or conventional fish meal diet. Importantly for the welfare of the salmon, they found no difference in immune function between the diets (Bransden, Carter, and Nowak 2001). Pratoomyot et al. (2010) examined four diets consisting of gradually lower fish meal contents at lower marine ingredient usages closer to what we currently see used in Norway and likely in Scottish salmon aquaculture. In the study, they replaced fish meal with plant protein in diets containing compositions of 25%, 18%, 11%, and 5% fish meal. They found that with each reduction in fish meal content, there was a reduction in the growth rate of the fish. The authors suggest this was due to the decreased palatability of these compositions to the salmon (Pratoomyot et al. 2010). However, at these lower levels it appears that supplementation with fish protein hydrolysate can offset the negative effects on growth - such as with 10% supplementation when reducing fish meal content from 35% to 5% (Egerton et al. 2020).

Although this is not a full review, we can still see the general trend that a redcued fish meal percentage lowers growth rates unless the feed is carefully formulated or supplemented with other ingredients. This general trend makes it unlikely that the industry will remove too much fish meal for the welfare of the salmon since doing so also reduces productivity.

11.2. Industry CoGP

Relevant points from current CoGP guidance (“Code of Good Practice Chapter 4: Seawater Lochs” 2015):

  • “Farmers should ensure, through labelling information or documentary assurance, that they use feeds that have been formulated for the species and life stage of fish being grown.”

Relevant points from current CoGP guidance (“Code of Good Practice, Chapter 7: Company Headquarters” 2015):

  • “Feed should be sourced from suppliers who participate in the Universal Feed Assurance Scheme (UFAS), or, where this is not the case, farmers should obtain and hold on file written confirmation from their feed supplier that the feed supplied meets the requirements of UK and European legislation.”

The CoGP itself provides little guidance to producers on the issue of fish meal/oil use in feed. It does refer to the Universal Feed Assurance Scheme (AIC 2016). However, the UFAS allows fish meal and also fails to specify either a maximum or range of acceptable compositions for fish meal.

11.3. Summary

Scale: Large. Better guidance on diet compositions has the potential to affect a large number of salmon and, given that each salmon eats many other fish during its lifetime, an even greater number of wild-caught fish.

Severity: Unclear. It seems like careful reductions in the quantity of fish meal will have no effect on salmon welfare. The effect on the wild fish the salmon eat is less clear, with several uncertainties that would take more time to review than we have available for this report. Given that the industry has already reduced its fish meal usage significantly, additional improvement is likely to be more difficult and may occur on its own regardless of any additional guidance or legislation.

Strength of current CoGP guidance: No guidance exists.


12.1. Welfare

In order to address certain environmental and fish health issues, the use of closed containment systems for the raising of adult salmon may become popular in the future. Closed containment systems can be on land or in water, but the basic concept is that fish are completely enclosed from the surrounding environment. This means that water quality and waste products can be managed using machinery.

Closed containment systems have certain significant welfare advantages over standard salmon farming. Sea lice and diseases would likely be drastically reduced in such systems. There is also no threat of predators and escapes are less likely to happen.

However, there are some serious concerns about the welfare implications of these systems. One of the biggest concerns is that, with a reduction in the potential for disease and an increase in control over water quality, farmers could increase their stocking densities. This would mean that salmon would suffer from an even greater reduction in living space and the likely stress and aggression that would accompany this. Existing certification schemes may mitigate this threat. Furthermore, closed containment systems require water to be continuously moving in one direction. This means that salmon that are ill cannot rest as they are pulled by the water movement. Another concern raised by Compassion in World Farming is that these systems will be completely reliant on the continuous operation of powered machinery and any backup systems. This means that any lapse in power supply, or human error, can have catastrophic consequences for the salmon. An example of this occurred in 2019 when 1.5 million juvenile salmon died at a hatchery owned by Mowi Scotland Ltd because of a human error that resulted in the recirculation pump stopping (CIWF 2021). Still, this risk may be acceptable given the other benefits of the system.

12.2. Industry CoGP

There is currently no policy in the CoGP on the use of closed containment systems for growing adult salmon.

It would have been good if the CoGP had taken a forward-looking perspective on this issue and made sure that some welfare guidance was already in place if these systems are used in the future.

12.3. Summary

Scale: Unclear. The use of closed containment systems for the on-growing of adult salmon is not yet a reality. However, investment and research in the area suggest that it is a likely pathway in the future once the technical hurdles have been overcome.

Severity: Unclear. There are several notable welfare benefits of closed containment systems. However, increases in stocking densities over existing systems are a particular concern.

Strength of current CoGP guidance: No guidance currently given. The Code does not mention the future use of closed containment systems (although some guidance is provided on the use of current closed containment systems for hatcheries and juvenile salmon).


Salmon and cleaner fish that are farmed in Scotland suffer many different welfare infringements, which paint a poor picture of welfare in the industry when put together. In particular, sea lice, sea lice treatments, cleaner fish welfare, and slaughter are notable areas of concern.

Improvements to the welfare of Scottish farmed salmon and cleaner fish should be made as a matter of urgency. It is clear that the current regulatory situation in the industry is failing to prevent millions of fish suffering poor welfare each year.

Whilst any Code of Practice can only advise on how farmers can comply with the law, our analysis of the current industry CoGP shows that it is vague and lacking guidance in many crucial areas. If an official Code of Practice were to be adopted by the Scottish Government, it would be best if that Code were as clear and comprehensive as possible in its guidance.



Though we should be cautious in our interpretation of them, surveys generally suggest that the UK public wants more action on fish welfare. In general, our understanding of the polling data about the public’s concern for fish is that it is somewhat less than for other animals, but not dramatically less. It appears that most people think that fishes’ mental capacities, including capacity to feel pain, are significantly lower (Saulius Šimčikas 2020).

The most relevant data we found was a poll by YouGov and The Humane League. This found that ‘when presented with the facts’, only 28% of the public surveyed in the UK agreed that aquaculture can be relied upon to ensure fish welfare without a legal requirement to do so. Meanwhile, 71% agreed fish should have the same detailed legal requirements for slaughter as pigs, chickens, and cows (Daw 2021).

Another highly relevant data point is that 76% of the UK public believes that fish should be protected to the same extent as other animals they eat (CIWF 2018). The strict implications of these statistics is that they suggest the public would be in favour of an official Code of Practice for farmed fish in the UK since there are Codes of Practice for land animals commonly farmed in the UK. However, people are unlikely to have thought through the full implications of their answers to survey questions so this data should not be taken at face value. Nevertheless, the polling process run by YouGov and The Humane League informed the participants about the industry beforehand, which represents significantly stronger evidence of their considered opinions.

Including some data from Europe more broadly, 89% of people believe that humane slaughter is essential for good welfare, 79% of people believe that fish welfare should be better protected than it is now, and 73% of them also believe that fish feel pain (Waley et al. 2021).

These are all encouraging signs, but we are sceptical that people would act according to these stated opinions about protecting fish. We suspect that many individuals are far less willing to protect fish in practice. Fish welfare has consistently been a much more neglected issue than the welfare of other animals, which suggests it is a cause that people care less about in practice (FWI 2019).

There are also some surveys that are at odds with the data presented above. For example, a 2007 Eurobaromater poll found that only 8% of EU citizens thought that fish welfare needed to be improved (Banrie 2022).

Public awareness and knowledge of aquaculture also appears to be low. Many people were surprised that the industry is as large as it is, such as that close to half of the fish they consumed were from aquaculture (Banrie 2022). This lack of awareness may mean that the issue is not emotionally salient to the public, even if in the abstract they say they support stronger protections.

European public concern for aquaculture centres more strongly around the sustainability and “naturalness” of the practice. Aquaculture is seen as more industrial and less natural than wild caught fishing and is seen less favourably in general (Katrin Schlag and Ystgaard 2013).


Scotland is currently being led by an unofficial coalition of 64 Scottish National Party MPs and 7 Scottish Green MPs. This puts the Scottish Green party in a position of unparalleled power. Scottish Green MPs are concerned about the aquaculture industry. For example, they want to phase out salmon farming and want a general moratorium on expansion of the industry until necessary environmental and animal welfare discussions are had (Editors n.d.). This makes it a particularly favourable time to work on this subject.

Given this, support from specific ministers may be particularly important since the government already has regulation in place to produce an official Code of Practice that covers welfare, it has just failed to do so. The main person in charge of both agriculture and animal welfare in Scotland is Mairi Gougeon, the Cabinet Secretary for the Rural Economy and Connectivity, supported by Mairi McAllan, the Cabinet Secretary for the Environment, Climate Change and Land Reform (The Scottish Government n.d., n.d.).

With respect to the ongoing review, Mairi Gougeon has said:

  • “This is a comprehensive piece of work by Professor Griggs and I am very grateful to him for the significant amount of time and effort that has gone into delivering it.”

  • “I welcome the ambitious range of recommendations he has made and we accept them all in principle.”

  • “Aquaculture is a significant contributor to our rural economy, providing well paid jobs in some of Scotland’s most fragile communities and will be an essential part of our green recovery and transition to net zero.”

  • “It is important that change to the sector is delivered in a practical way that reflects the co-operation agreement with the Scottish Green Party and our own manifesto commitments.”

  • “Developing world-leading legislation for aquaculture is key to developing a sector that is both environmentally and economically sustainable.”

  • “We will take a short amount of time to consider the proposals, and maintain the momentum of this important work.” (The Scottish Government 2022)

Similarly to the review itself, she does not mention animal welfare, and she is clearly supportive of the industry overall. However, it is encouraging that she is ready to reform the industry and that she has accepted Professor Griggs criticisms of the current regulatory framework.

On the general subject of animal welfare, and in response to the animal welfare commission, she shared the following: “Animal welfare is a subject that I feel very passionately about so I’m delighted to announce Professor Dwyer as the first Chair of the independent Scottish Animal Welfare Commission who will bring a depth of expertise and knowledge to the Commission.

“I have tasked the Commission to look specifically at how our current policies take account of the welfare needs of sentient animals, what improvements could be made and report back to me with their conclusions.

“I’m proud of Scotland’s high standards when it comes to animal welfare and believe this step will strengthen those standards even further. I look forward to working with Professor Dwyer to ensure we have the highest standards of welfare for our animals.”(James 2019)

Mairi McAllan also has a record on animal welfare. She has put forward legislation to close the loophole allowing foxhunting and to ban glue traps in Scotland (Gordon 2022; Mason 2022). Having said this, general work on animal welfare provides only weak indications for a willingness to work on salmon welfare.


The Scottish National Party and Scottish Green Party coalition has already seen improvements for Scottish aquaculture (Fish Farmer Magazine 2021). In September 2021, the Scottish government (The Scottish Government 2021) published a Code of Practice for Scottish aquaculture concerning fish escapes and marine mammal interactions. Fish escapes and marine mammal interactions certainly have welfare implications, but the welfare of fish is unlikely to be the main motivation behind this, and these would just be a small part of what a full official Code of Practice would address. Nevertheless, the fact that the Scottish government has already taken action in this area could lend a great deal of strength to a campaign to establish a broader Code of Practice for Scottish aquaculture.

An article by The Herald (Grant 2021) describes the motivations behind the Code of Practice. A government spokesperson quoted in the article describes their plans for actions on this issue, including introducing punishments for fish escapes. Intriguingly, the spokesperson also mentions that they want to take action on sea lice and Scottish aquaculture. As part of the agreement for the coalition, the government has pledged to strengthen controls on sea lice and to ban fishing and aquaculture from a protected area encompassing 10% of Scottish waters (Fish Farmer Magazine 2021). This follows the Scottish government’s banning of the killing of seals by Scottish salmon farmers (Carrell 2020).

The first stage of a review of the regulation of Scottish aquaculture was published on February 10, 2022 (Griggs 2022). This review states that there is an urgent need to improve regulation of the industry. Though not a central topic by name, the issue of a lack of an official Code of Practice is specifically mentioned once in comment 6 of the review:

“For salmon farming to grow sustainably in Scotland, it is essential that all salmon farm operators manage their farms within the environmental limits of the surrounding marine environment. Whilst an industry code of practice exists, which is largely follow ed by the industry, it is important that any cases of poor farm management and unacceptable environmental impact are detected, and that farm managers, and parent companies, are held accountable. A single consultation process, led by a single body, would be a more efficient process. It would allow for all concerns to be raised and considered together, and for adequate resources and expertise to be available to scrutinise every aspect of a new salmon farm proposal. Existing and new regulation need to meet the tests of being robust, transparent, enforceable and enforced. To ensure environmental impacts of salmon farming are identified and addressed, and therefore deliver environmentally sustainable growth of the industry, it is essential that salmon farm operations are reported on and monitored in a transparent way.”

Many other parts of the review also suggest consideration of the issue:

“In carrying out my review I asked the following questions:

• Why does the sector need regulation in the first place?

• Why has that regulation to be in the form of legislation rather than self regulation by the industry?

• What are the issues with the current regulatory framework?

• What could be done to improve the current framework and importantly the process?

• Are there any examples that might provide useful insight on how this is done elsewhere?”

The Scottish government has since accepted the results of the review so far (Global Seafood Alliance 2022). This ongoing review suggests that the industry will see massive changes, making it a promising time to ensure welfare is prioritised in this process by advocating for a broader Code of Practice that would consider fish welfare in detail.

Based on these factors, we conclude that this subject is on the table for the Scottish government and that the current policy window for establishing an official Code of Practice in Scottish Aquaculture is highly promising.


As mentioned above, the Aquaculture and Fisheries (Scotland) Act 2007 gives the Scottish government the power to create an official Code of Practice for Scottish aquaculture. We therefore do not anticipate legal hurdles for this ask.


The recent actions of the Scottish government are encouraging about the odds of success of a campaign to establish an official Code of Practice. However, they bring with them the concern that a Code may be established even without action on this point. If an official Code of Practice is already inevitable, this ask would have little to no value.

The recent Code had a consultation period before it was introduced into law (The Scottish Government n.d.). In their analysis of the comments during the consultation, there was no mention of comments taking issue with the fact that the Code does not cover animal welfare. Indeed, there was no mention of animal welfare at all in the consultation analysis and we did not see the names of any animal advocacy charities among the names of the commenters (though some commenters did suggest a need for further regulation). This suggests that this specific angle is neglected, even as the Scottish Government moves in a consonant direction that will bolster work on the subject. In short, while there is an acknowledgement that the industry needs better regulation, animal welfare is largely being left out of the conversation. There is therefore a good opportunity to raise the lack of a welfare Code of Practice, given this is a natural extension of the ongoing work on this subject.

Despite this lack of presence in response to the consultation, there are several animal advocacy organisations working on Scottish aquaculture. OneKind is a Scottish animal advocacy organisation that has a longstanding campaign against Scottish aquaculture (OneKind 2018c). This campaign has the aim of stopping the expansion of the industry until a life worth living can be ensured for farmed fish and until other wild animals are no longer harmed by the industry. As part of this campaign, they have contributed to government inquiries on the subject, given presentations on the subject, and written several reports which we referred to earlier.

One of these recent reports, Underwater Cages, Parasites, and Dead Fish was conducted with another organisation working on this subject, Compassion in World Farming. Like OneKind, Compassion in World Farming also calls for a moratorium on the expansion of the industry. Compassion in World Farming is working on Scottish Salmon as part of their broader “Rethink Fish” campaign (CIWF n.d.).

The Humane League UK also has a campaign against the Scottish salmon industry. Their campaign stresses the importance of official regulations, though in their case this centres around slaughter (THL n.d.). In addition, `Animal Equality is also running a campaign for improved regulations for fish slaughter. Their work has centred around an undercover investigation done on Arnish Farms where they documented many fish being haphazardly and improperly stunned (Animal Equality 2021). Many of these animals therefore died while fully conscious.

Viva! also has a campaign against the Scottish salmon farming industry that centres around an undercover investigation (Viva! 2020). Additionally, they have a similar investigation and campaign against Scottish trout farming (Viva! 2021). Viva!’s bottom line is the end of factory farming.

Scottish Salmon Watch is another organisation working on this (SSW n.d.). They have protested supermarkets and conducted investigations, research, and media campaigns against the industry.

Finally, Advocates for Animals are a UK-based law firm that uses the strength of the law to help animals (AA n.d.). They have challenged the legality of the use of thermolicers as a method to control sea lice (Green Around the Gills n.d.).


In this section, you will find a summary of the conversations held between Animal Ask and various experts in this field. These experts have a range of experience in fields such as legislation and policy, campaigns, undercover investigations, and industry professionals. The identities of these individuals will not be made public in order to protect them. However, with express permission from the individuals concerned, certain further information and/or their identities may be shared if this resource is of value to your work. If this is of interest, please get in touch with us.

Overall, the experts we spoke to were generally supportive of an ask that requests the Scottish government acknowledge and improve the lack of regulatory framework for salmon farming in the region. They agreed that the lack of regulatory framework within this industry was problematic, with two main factors being emphasised across all interviews:

1) Salmon farming is a highly political issue due to the negative welfare of the animals, environmental concerns due to pollution, and the reliance on this industry for job security throughout Scotland.

2) Salmon are a species that are generally not suitable to be farmed due to their sensitivity and inability to adapt to intense factory farming conditions.

Political Issue: Many experts spoke of the challenges with campaigning against the salmon industry due to the political power it holds through its contribution to the economy. They agreed that leaving the regulation and enforcement of salmon farming to external bodies was not appropriate and is something the government should be forced to ensure. However, experts saw little political will for change. It also seems that due to the 2021 parliamentary elections in Scotland, any progress in this area has been halted.

Welfare Concerns: Experts were concerned with the overall lack of welfare regulation for farmed salmon with multiple issues repeatedly cited. Mortality rates, sea lice, heart disease, gill damage, and skin damage were just some of the welfare concerns highlighted. Many of the welfare issues were cited as being a by-product of salmon being an unsuitable species to mass farm due to their natural sensitivity.

Specificity of the ask: One experienced fish expert suggested that rather than tackling one element of the welfare of the salmon, campaigning for the overhaul of the full system, whilst time-consuming and a large undertaking, would be the best method. With all of the intricacies involved in the decision-making, tackling the issue under a wide umbrella would likely have the greatest overall impact.


This section summarises our cost-effectiveness analysis (CEA), which weighs organisational costs against the welfare benefits of the ask. However, some parameters are subject to high uncertainty, and CEAs generally face a number of limitations (S. Šimčikas 2019; Holden 2016). The results of this CEA should be taken in light of these uncertainties and limitations.

Modelling the effects of this ask is much more difficult compared to our other priority asks as there are several steps between a successful case and improvements in the industry. This means that while the maximum impact this ask could have is potentially very large, there are several points that could cause even a successful case to have little or no impact. This problem is compounded by the difficulty of estimating some of the effects this ask could have, such as building the groundwork for future legislative or enforcement campaigns which were not included in the CEA. It is important to note that these non-quantifiable effects may be very significant, and that cost-effectiveness models are necessarily limited by their inability to capture these effects. In light of this, the results of this cost-effectiveness analysis are very uncertain.

There are numerous potential benefits to this ask, but predicting exactly what will occur is difficult. An overarching campaign like this could lead to improvements on many aspects of the unofficial Code of Practice. In this CEA, we have modelled the expected effect of improvements occurring for sea lice numbers, sea lice treatment methods, reduction in the use of cleaner fish, reducing escapes, environmental enrichment, slaughter methods, stocking density, and water quality. Each of these could potentially significantly improve the quality of life for any fish who benefits from them. However, some elements are difficult or impossible to make improvements on compared to current industry practices. For example, in the case of sea lice, improvements are very difficult to make practically and treatments for the issue are themselves potentially detrimental for the welfare of the fish. The elements we would be most interested to see improvements on are cleaner fish, slaughter, and environmental enrichment. However, many of these issues would require a substantial change to the Code of Practice or additional research to support amendments, which are unlikely in the short-term.



There are numerous existing Codes of Practice for other farmed animals including cattle, chickens, sheep, and pigs. These existing Codes of Practice were created a long time ago and have been edited and updated many times over the years. If the ask is successful, then the Scottish government may adopt the existing industry CoGP, create an official Code of Practice, or revise the existing Code of Practice so that it covers fish welfare more comprehensively.

If a new Code was created, it would be opened up for consultation, as the recent limited Code was (The Scottish Government n.d.). This would allow various individuals and organisations to submit their views on the new Code, including seeking amendments and/or additions. In the past, views have been submitted by animal advocacy organisations, industry bodies, and universities (DEFRA n.d.). We have noted that many welfare issues are either not addressed, or only addressed using very vague language, in the industry’s CoGP. For example, words such as ‘adequate’ are used in places where specific, quantifiable guidance could be given based on available scientific evidence. This lack of specific guidance on welfare issues reduces the enforceability of the code. There may be some scope to improve this situation if the Government chose to create a new Code rather than adopt the industry CoGP verbatim. However, Code of Practices can only advise on how to adhere to existing regulations, so any improvements will be limited by the extent of the law.


The best predictor of future enforcement and compliance with a new official Code of Practice is current compliance with other laws, certification schemes, and the current industry Code of Practice. However, given how vague a lot of the terminology is in the code and that the majority of the code is not official government guidance, most of the code is unenforceable without amendments.

The clearest example with a specific threshold and sufficient data to examine is the requirements surrounding sea lice. The industry Code of Practice advises lice treatment at between 0.5 and 1 adult female sea lice per fish depending on the time of year (Organisation 2016). This is lower than Marine Scotland's standard old requirement for farms to report any weekly sample that exceeds an average of two adult female sea lice per salmon and the mandate of immediate action if this exceeds six (Marine Scotland 2021). If farms fail to rectify the situation, an enforcement action will be taken. Sea lice data from Marine Scotland shows that monthly average sea lice levels exceeded six per fish 17 times, and two per fish 472 times, on farms between 2018 and 2020 (“Sea Lice Count Data 2018-2020 - Historical Sea Lice Data for Scottish Salmon Aquaculture 2010 - 2020” n.d., “Sea Lice Count Data - 2018-2020” n.d.). The requirements for reporting have changed since this data was collected, now ‘requir[ing] sea lice numbers to be reported weekly in arrears for all sites where fish are farmed’ and reasons must be given if no count is reported (Fish Health Inspectorate n.d.).

Recent data shows that each time a farm exceeds an average of two sea lice per fish they report either intended or current mitigation methods in compliance with regulation (FHI 2021). It is worth noting that farms below this threshold and above the industry Code of Practice suggestions do not report any mitigation methods, possibly in violation of the Code of Practice. Even so, advisory notices were sent to three and five of the farms that exceeded the upper threshold of six sea lice per fish in 2020 and 2019 respectively. No advisory notices were sent in 2018 but 8 breaches were recorded which would require enforcement notices (“Fish Health Inspectorate: Sea Lice Information” n.d.). From the existing data for sea lice, we can see that most farms comply with government regulations and those that don't receive the appropriate disciplinary action. In regards to the industry Code of Practice, it is unclear whether farms attempt to comply with the lower threshold for action set by the industry Code of Practice.

We can see other indications of current compliance rates through undercover investigations. Each of these provides us with a case study of individual farms’ practices rather than a view of the full industry, but nevertheless provide some evidence of compliance rates. The two most prominent recent investigations are from Animal Equality (Animal Equality 2021), Compassion in World Farming and One Kind (Compassion in World Farming n.d.). In total, these investigations cover 22 farms and a slaughterhouse. On several farms, 'investigators found severe sea lice infestations and high levels of mortalities’ (Compassion in World Farming n.d.) and evidence of ‘animals suffering from prolonged pain’ was found in the slaughterhouse. However, neither of these are evidence of non-compliance with existing specific regulations and codes, though one could argue this amounts to unnecessary suffering. The investigation in the slaughterhouse actually shows the best-known slaughter method for salmon, percussive stunning followed by gill slitting, even if it was poorly executed in the footage they gathered.

The third avenue to investigate compliance rates is how well farms comply with other standards such as assurance schemes. This is also an important thing to consider as these schemes already exceed existing regulation and the CoGP in many areas. This means that compliance here will reduce the number of animals affected by an improvement in regulations. The RSPCA assurance scheme is the most widely subscribed to scheme in UK aquaculture, with around 70% of Scottish salmon certified (“What Is RSPCA Assured?” n.d.). The RSPCA provides statistics about their regular assessments of farms: ‘Of the 3,173 assessments completed in 2019, 44% had one or more non-compliances recorded. The vast majority of those were very minor, however 17 (0.5%) had severe animal welfare related non-compliances which resulted in immediate suspension from the scheme and subsequent investigation.’ (“RSPCA Assured Annual Review 2019” n.d.) The average number of infractions was 2.3 per assessment but, given that the RSPCA have 368 standards per species on average, this is a small proportion. CIWF and One Kind’s undercover investigation of salmon farms potentially demonstrated non-compliance with the RSPCA standards. However, the RSPCA initially suspended their assurance and reinstated it after subsequent investigation (Moore 2021b). Until now, these visits have been pre-arranged with the farm but after the recent investigations from CIWF, some figures from the SSPO are encouraging the RSPCA to make unannounced visits (Compassion in World Farming n.d.; Moore 2021a) .

Overall, it seems that most of the industry tends to comply with the industry Code of Good Practice Although given the current code is made by the industry is very vague, proving non-compliance is difficult. Most farms are RSPCA-assured and their enforcement mechanisms through farm assessments and monitoring surpass what we would expect from government bodies. Of the remaining 30%, it seems that most farms tend to be compliant even if occasional infractions likely occur. Given the vague and weak protections the industry Code of Good Practise provides, this compliance does imply meaningful protection. Still, there is some weak evidence that an official Code of Practice would be complied with thus improving the quality of life of fish in aquaculture.


Given most of the industry seems compliant with the RSPCA’s welfare standards, a new official Code of Practice will either have to exceed these standards or will have a much smaller effect on these farms. Whilst the actionable change on the farms may be smaller with those already complying with RSPCA standards, the precedent set by the government through a code would impact the full industry. The table below provides a comparison between the industry CoGP and the RSPCA standards on some key welfare issues in UK aquaculture.

Key Welfare Issue

Code of Good Practice for Scottish Finfish Aquaculture (CoGP)

RSPCA welfare standards for farmed Atlantic salmon

Sea Lice

Regularly sample 25 fish, Treatments for averages above 0.5-1 adult female

Prevention programme with a veterinary surgeon, record sea lice damage to fish, humanely kill fish with severe damage

Sea Lice Treatments

Require risk assessment for methods of sea lice removal

Require risk assessment for methods of sea lice removal

Clearer Fish

Allows cleaner fish, suggests hatcher reared, should be health checked free of pathogens, humanely destroyed after production, ‘adequate provision of hides’, ‘Supplementary feed’, can be reused only once after a health check

Require operating procedure for identifying and humanely capturing and killing cleaner fish, ‘ humanely handled and/or killed without delay’, requirements for cleaner fish welfare at all life stages or if wild-caught


Contingency plans, daily visual inspection of the holding units, reported immediately to all relevant stakeholders, recapture agreed on with local District Salmon Fisheries Board, check nets during harvest

Site-specific containment plan, Enclosures designed to avoid damage from poor weather, Suitable nets to avoid escape or entanglement

Triploid Fish


The RSPCA are investigating usage and welfare needs to ultimately determine whether they will be allowed to be used in future under the standards

Stocking Density

‘Adjusted in line with the biological and behavioural needs of fish having regard to the prevailing environmental conditions and, in particular, water quality’

‘The stocking density in freshwater enclosures must not exceed 8 kg/m, Seawater enclosure 17kg/m³,

Seawater enclosure site maximum 15kg/m³ and requirements in transit and earlier life stages

Water Quality

‘Emergency back-up systems to maintain a high standard of water quality‘, contingency plans, ‘Farmers should monitor oxygen levels during crowding and take corrective action if levels fall below a critical point for that species‘

Training in visual signs, record keeping, action must be taken if water quality falls outside of an acceptable range, full standards on pg26, maintained in transport

Environmental Enrichment


For salmon, aware of trials examining fin damage and may update future standards. For Wrasse (cleaner fish) over 10 grams, suitable environmental enrichment, such as artificial kelp and hides, must be provided when in tanks


No mention of welfare or stunning

Minimal crowding and handling, rapid painless method of killing, ‘Humane mechanical devices must be used in preference to a manual percussive blow’, percussive or electrical stunning followed by bleeding, ‘The number of fish that have not been effectively stunned must be recorded’, check systems before harvest

Fish Meal & Fish Oil

N.A (correct feed for life stage)

N.A (in line with regulation)

Wild Mammal Deterrence

‘Farmers should have standard operating procedures’, killed with a licence but suggest non-lethal methods, ‘Acoustic deterrent devices (ADD) should be used where and as permitted’

‘Humane precautions must be taken to protect salmon from other animals that could cause them harm, including bringing in disease’, recording an maintenance on prevention methods such as nets

Future Development of RAS



Future Development of Offshore Farms



On most issues the RSPCA standards are fairly strong, with many welfare issues being addressed in addition to regulatory requirements. Given that RSPCA standards hold Scottish salmon farms to higher welfare standards than legally required on many welfare issues, the impact of introducing an official Code of Practice may be substantially reduced.


In 2019, Scotland produced 7,405 tonnes of rainbow trout. It is challenging to calculate how many individuals this represents, since this depends on the average harvest weight of the trout. Figures show that the majority of trout harvested in Scotland weighed more than 900g but provide no more detail on average harvest weights (Scottish Government 2019). Another source tells us that rainbow trout are often harvested at between 1.5 and 5 kg (Seafish n.d.). Assuming an average harvest weight of 3kg, this would mean that approximately 2.5 million rainbow trout were raised that year. If we assume a lower average weight of 1.5kg, this would be 5 million individuals. Therefore, we can conclude that while worthy of significant consideration, the number of individual trout raised in Scotland is somewhere around 1:10 and 1:20 in relation to the number of salmon.


The lack of an official Code of Practice covering Scottish salmon farming creates ambiguity around how salmon producers should comply with welfare law. Our review of welfare on Scottish salmon farms, alongside those of other animal advocacy organisations, shows that there are multiple serious welfare issues that are impacting salmon and cleaner fish. The current state of fish welfare in Scotland suggests that the Scottish Government must step in to improve standards. Creating a new official Code of Practice would be one step towards doing so. However, the fact that over 70% of Scottish salmon farms are accredited to the RSPCA or the Soil Association Organic standards - which often go beyond legal requirements - makes us more sceptical of the impact that an official Code of Practice might have for many of these problems. This concern is especially strong if the official Code of Practice were to contain a lot of vague or ineffectual guidance, as is currently the case with the industry CoGP. The case for a more comprehensive Code of Practice would be strongest if it is corrected for existing weaknesses in the CoGP, such as the lack of protections for cleaner fish or requirements for specific stocking densities.

Although there is likely a strong case for a more comprehensive Code of Practice in principle, the question remains of what improvements we would expect to see in the quality of life for Scottish salmon if this was successful. There are several areas of welfare that could potentially be improved if an official Code of Practice (or broader overhaul of regulations) were achieved. However, predicting which aspects of welfare would improve as a result of the establishment of an official Code of Practice is difficult. There are also harder to quantify long-term effects of an official Code of Practice that are important to consider, such as increased accountability for farmers, a more serious attitude towards fish welfare by the Scottish government, and opening up opportunities for future advocacy.

It is a particularly good time to work on this issue because the government is reviewing the regulation of the industry and beginning to implement significant changes, such as the recent Code of Practice for Scottish aquaculture concerning interactions with marine mammals. Though welfare currently does not figure prominently in this conversation, the ground is fertile for a greater emphasis on it, and this opportunity is neglected.



1. Associated secondary legislation: The Fish Farming Businesses (Record Keeping) (Scotland) Order 2008 and The Fish Farming Business (Reporting) (Scotland) Order 2020.

2. “However, much of the governance of fish farms in Scotland is conducted under the Code of Good Practice but, as the code is nonstatutory, auditing of compliance with its terms is a matter for industry itself.”

3. Grieg Seafood Shetland were expelled from the CoGP for violating quarantine rules on importaning smolts from Norway (Source Seafood n.d.).

4. We have seen some evidence that the number of farms certified by the RSPCA may have increased, although we are unable to confirm.

5. Note that we have spent a limited amount of time examining current CoGP guidance on each issue and generating ideas for how it could be improved. Our goal is just to provide a rough sense of how well the Code performs on each issue.

6. We note that AfA are currently pursuing a legal case against thermolicers.

7. Various estimates appear to exist for cleaner fish use in Scotland which do not necessarily all tally together (Open Seas 2017).

8. 73,000 escaped in one single event.

9. The use of closed containment systems at the hatchery stage is already common.


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