Sea lice rampant on salmon farms

Shocking photos show sea lice rampant on salmon farms in Scotland

Shocking footage passed to Salmon & Trout Conservation Scotland reveals horrendous sea lice parasite problems currently occurring on salmon farms in Argyll & Bute, Skye and the Outer Hebrides.

The appalling conditions documented on Vacasay salmon farm on the Isle of Lewis in September 2018 ( are now being repeated at numerous locations.

Loch Creran, Oct 2020

In its damning report on the salmon farming industry in November 2018, the Scottish Parliament’s Rural Economy and Connectivity Committee was adamant that “the ‘status quo’ in terms of regulation and enforcement is not acceptable.”

Andrew Graham-Stewart, Director of Salmon and Trout Conservation Scotland (S&TCS), said:

“The images and footage passed to us are truly shocking. It seems that little, if anything, has changed, since the 2018 Parliamentary Inquiry, in the way that salmon farms are managed to address escalating sea lice parasite issues. The Scottish Government has failed to introduce a proper regime of regulation and enforcement on salmon farms and consequently parasite and disease issues are being allowed to run riot.”

One of the most severely affected salmon farms, in Loch Creran, is owned by Scottish Sea Farms Ltd. The company is the exclusive supplier of farmed salmon to Marks & Spencer. Recent treatments at the farm, including Thermolicing (passing the farmed salmon through heated water to shock the sea lice off the salmon) and bathing the fish in Hydrogen Peroxide, appear to have had minimal effect. Indeed, large numbers of mature sea lice are clearly visible in the footage which was shot on 22 October, shortly after these treatments.

View sample footage: HERE


Investigators who passed the footage to S&TC have documented severe sea lice eruptions concurrently at salmon farms near Oban, Lochgilphead, Dunvegan, Broadford, Loch Maddy and Loch Boisdale. No investigations were conducted on Orkney or Shetland.

These images from a salmon farm on Skye captured on 26 October, show the horrific injuries sea lice parasites may cause when they are left for weeks to eat the skin of the farmed salmon and expose large areas of flesh.

Skye, Oct 2020


While S&TCS’ focus is the health of populations of wild salmonid fish, it is clear that sea lice inflicting such damage to farmed salmon means that farms are simply not being managed properly and that is bound to have knock-on effects on wild fish.


Nick Measham, CEO of Salmon and Trout Conservation UK, said:

“Badly managed fish farms have severe implications for wild fish, especially when salmon farmers allow sea lice numbers to run out of control.

Anyone with a shred of decency should be sickened by the condition and suffering of these farmed fish. Will the UK really be able to claim it has higher animal welfare standards than other countries such as the US when the Scottish Government allows this to happen?  How does this type of image sit with claims being made over farmed animal welfare in advance of UK-US trade talks?"

Independent monitoring of sea lice on salmon farms is desperately needed.

The monitoring and publication of sea lice numbers on salmon farms is entirely reliant on self-reporting by the salmon farmers themselves.

Andrew Graham-Stewart added: 

"We have no doubt that the appalling lack of control over sea lice on salmon farms will continue until such time as Scottish Government introduces a rigorous regime of independent monitoring and verification. Without such a regime, farms will continue to be run ‘out of sight and out of mind’ of the regulators, with devastating consequences for Scotland’s wild salmon and sea trout.” 


Issued by (T: 07463 576892).

Notes for editors

1) Salmon & Trout Conservation UK (S&TC UK) was established as the Salmon & Trout Association (S&TA) in 1903 to address the damage done to our rivers by the polluting effects of the Industrial Revolution. Since then, S&TC UK has worked to protect fisheries, fish stocks and the wider aquatic environment for the public benefit. S&TC UK has charitable status in both England and Scotland (as S&TCS) and its charitable objectives empower it to address all issues affecting fish and the aquatic environment, supported by robust evidence from its scientific network, and to take the widest possible remit in protecting wild salmonid fish stocks and the aquatic environment upon which they depend.

2) What is the problem with sea lice? ( levels of these parasites occur naturally in the sea. However, the advent of salmon farming, particularly in fjordic or largely enclosed sea lochs, has led to a fundamental change in the density and occurrence of sea lice in parts of the coastal waters of the west Highlands and Islands. Even one or two mature female sea lice per fish within a set of cages housing hundreds of thousands of farmed salmon amounts to a very large breeding reservoir producing huge numbers of mobile juvenile sea lice that move out into the local marine environment. The consequences for wild salmon and sea trout smolts, the metamorphosing fragile skin of which is not adapted to cope with more than a few lice, as they migrate from local rivers to sea can be devastating. Lice feed by grazing on the surface of the fish and eating the mucous and skin. Large numbers of lice soon cause the loss of fins, severe scarring, secondary infections and, in time, death. Badly infested wild salmon smolts disappear out to sea, never to be seen again. In contrast afflicted sea trout smolts remain within the locality and they, together with the impact of the deadly burdens they carry, are more easily monitored.

Don’t just take our word for it

The Salmon Interactions Working Group proposals to protect wild salmon and sea trout will not work.

But don’t just take our word for it…..

The Salmon Interactions Working Group (SIWG), which includes Fisheries Management Scotland (FMS), has proposed a system of adaptive management, through the sampling of sea trout in sea lochs by netting, “to monitor lice levels in the environment and assess impacts on wild salmonids”. In the event that such monitoring shows elevated numbers of sea lice, then possible changes to the management of lice levels on the local salmon farms would be discussed.

1) Such adaptive management cannot be a realistic substitute for proper regulation including a strict and universally applied ceiling on farm sea lice numbers (an absolute upper limit to the permitted average number of adult female sea lice per farm fish). But don’t just take our word for it.

In a letter to Highland Council in February 2018, the Chairman of the Wester Ross Area Salmon Fishery Board (also a Board member of Fisheries Management Scotland and an employee of Atlantic Salmon Trust) said:

"If sea trout or wild salmon were to completely disappear at monitoring locations (as may happen), there would be no way to demonstrate cause and effect……Monitoring of wild fish to inform the management of salmon farms for the benefit of wild fish populations in nearby waters is no substitute for appropriate regulation of open cage farms to safeguard wild fish."

2) The monitoring of lice levels on sea trout by netting to inform the management of salmon farms is indeed fraught with difficulties. But don’t just take our word for it.

FMS, which represents Boards and Trusts, published a paper in January 2018 on sea trout post smolt monitoring. It concluded:

“Attempting to link sea lice levels on wild sea trout to the nearest fish farm may not be appropriate, as prevailing wind direction and sea currents may transport fish farm derived sea lice away from salmonid rivers (Adams et al. 2012), and sea trout in the marine environment are mobile and can interact with more than one fish farm” and  “… order to better manage the interactions….will require a greater understanding of the lice populations, their build up within the cages and wider environment and the impacts on the wild salmonids. Until these issues are better understood local management will remain difficult”. See

3) Under the SIWG proposals, in a rejection of the standard precautionary approach, it is envisaged that the burden of proof that there is damage being caused to wild fish by salmon farms (before there is any possibility of remedial action in terms of fish farm performance) is the sole responsibility of wild fish interests. This is contrary to the basic principles of natural justice. But don’t just take our word for it.

In a letter dated December 2018 to Highland Council, regarding a proposed increase in biomass at the Loch Hourn salmon farm, the Wester Ross Area Salmon Fishery Board had the burden of proof the right way around…

“We therefore request that the applicant is able to demonstrate, contrary to the information presented above, that the previous increase in on-farm biomass in 2016 was not associated with further declines in wild fish stocks in the area, and that, contrary to the information presented above, that the high sea lice figures reported in SSPO fish health reports for 2016 and 2017 were not associated with high emissions of larval lice into surrounding waters….The applicant should demonstrate that the reported declines in catches of wild sea trout and salmon in the area from 2016 to 2017 were not associated with sea lice infestation associated with the Loch Hourn salmon farm”.

 4) Under adaptive management, establishing a pattern or trend in sea lice numbers through wild fish monitoring is not an exact science, nor can it be achieved quickly. It will take several years and, in the meantime, without a strict sea lice ceiling applied to all fish farms from the outset, wild fish would have no more protection from farm-origin sea lice infestation than is currently the case. Indeed, as a consequence of significant ongoing industry expansion, the sea lice burden and challenge for wild fish continues to rise and will inevitably rise still further in the first decade under an adaptive management regime. But don’t just take our word for it.

In a video conference call in July 2020 a senior executive from the Crown Estate Scotland (responsible for awarding and managing leases for fish farms) did not disagree that it would probably take intense monitoring of wild fish for at least three farm production cycles (up to six years) for any pattern of damage to wild fish caused by fish farms to be discernible.

 Even then the results are likely be challenged (including the use of the courts) by the fish farmers. See what is happening in Norway:

There are considerable doubts regarding the extent to which monitoring of wild sea trout is relevant to wild salmon. Even if there were abundant smolts of both species to sample, it would require tens of thousands of samples to be taken nationally, over many years and in many conditions, in order to produce a statistically robust dataset.

Previous studies in Loch Shieldaig by Marine Scotland Science, which sampled over 3,000 smolts (in sentinel cages) relating to just one system and salmon farm area, showed strong correlation with salmon farm lice numbers but crucially still did not meet a sufficient threshold of evidence to ensure control of sea lice on salmon farms. But it is now suggested that sampling less fish of another species by non-research professionals will going to produce enough evidence. What has changed?

5) We have serious concerns that local fishery interests (who will be contracted and paid by the salmon farmers to monitor sea lice on wild fish) will be reluctant to argue robustly for changes to local salmon farming practices when wild fish monitoring shows high levels of sea lice – he who pays the piper calls the tune.

Before the SIWG process Fisheries Management Scotland’s (FMS) position was that adaptive management on its own would not provide the basis for effective regulation, and that a robust sea lice ceiling should be applied to all farms.  Through the SIWG process, which required recommendations which were agreed by the Industry, FMS has aligned themselves with recommendations which do not achieve this. There may well be elements of the recommendations (particularly financial ones) which are beneficial for FMS and the Trusts. However, the compromise in relation to regulation will mean that it is not effective.

We believe that it is imperative that any new regulatory regime includes a strict adult female sea lice ceiling, to be applied to all fish farms. Sea lice must be independently monitored and where levels rise there must be rigorous and very prompt  enforcement to drive lice levels back down. , This ceiling should be set at 0.5 adult female lice per farmed fish, dropping to 0.1 during the period of wild smolt emigration, below which ceiling  any adaptive management, based on wild fish monitoring, is then applied. This position is based on best available science and in line with recommendations already made by SNH, the industry’s own Code of Good Practice and the Aquaculture Stewardship Council amongst others.

Salmon and Trout Conservation Scotland

October 2020

SNH and EA formally notified of threat of environmental damage from escaped farmed salmon

Salmon & Trout Conservation (S&TC) formally notifies NatureScot (formerly SNH) and the Environment Agency of threat of environmental damage to protected wild salmon SACs following the recent major escape of farmed salmon off the Mull of Kintyre

Following the major escape from a salmon farm off the east side of the Mull of Kintyre in August and the subsequent presence of large numbers of farmed salmon in Scottish and English rivers, Salmon and Trout Conservation has now formally notified the relevant authorities in Scotland and England of  environmental damage to affected Special Areas of Conservation (SACs) for wild Atlantic salmon that either has or may about to be caused to wild stocks.

This process, set down in European law, requires both the Environment Agency and NatureScot to undertake formal examinations of what has occurred and do what they can to prevent further damage occurring to the wild salmon populations in the SACs affected.

Almost 50,000 large farmed salmon were able to escape from Mowi (Scotland) Limited’s farm at Carradale North near Campbeltown on August 20. Since then farmed salmon have been caught in considerable numbers in rivers from the Firth of Clyde to Cumbria, prompting concerns that interbreeding with wild salmon will occur with implications for the vital genetic integrity and thus long-term viability of already depleted wild populations.

The affected rivers include three SACs for wild salmon – the River Endrick SAC in Scotland and the River Derwent and Bassenthwaite SAC and the River Eden SAC in England – which are subject to enhanced protection under the law in the respective jurisdictions.

Guy Linley-Adams, solicitor to Salmon and Trout Conservation, said:

“These notifications put  NatureScot in Scotland and the Environment Agency  in England, the competent enforcing authorities charged with ensuring that the integrity of SACs is maintained, on formal notice that damage to these SACs is either now occurring and/or that there is an imminent threat and that accordingly they should now take any necessary remedial action.”

The notification letter to NatureScot is supported by the Loch Lomond Angling Improvement Association (LLAIA), whose responsibilities include much of the River Endrick.

The notification letter to the Environment Agency is supported by North West Angling Trust Fisheries Consultative Council (NWATFCC) which represents the west coast game fisheries of Cumbria and Lancashire.

If either competent authority finds, following notification, that damage is occurring, then it is obliged to require Mowi to avoid further damage to the conservation status of the habitat and/or species and remedy damage already done.



1) The Environmental Liability Directive (ELD), which enshrines the “polluter pays” principle, was adopted in 2004. In Scotland, it takes effect through the Environmental Liability (Scotland) Regulations 2009.  In England it is covered under the Environmental Damage (Prevention and Remediation) (England) Regulations 2015

2) Scottish Government confirms that “escaped fish…… have the potential to interbreed with wild fish, leading to dilution of genetic integrity”. Research indicates that interbreeding of farmed with wild salmon results in lowered fitness, with repeated escapes causing cumulative fitness depression and potentially an extinction vortex in vulnerable populations. See, for example, McGinnity et al (2003) 

Not just another escape

As a moderate late summer storm abated, rumours that one of Mowi’s salmon farms between the Mull of Kintyre and Arran was in trouble were confirmed by a statement from the company:

“On August 20, 2020, Mowi’s salmon farm at Carradale North, consisting of 10 circular net pens containing 550,000 salmon (at 4.2kgs), shifted position after its seabed anchors became dislodged during Storm Ellen that has hit the UK and Ireland. The company’s priority at this time is to secure the fish cages in place until Storm Ellen subsides, and to safeguard staff, contractors and fish stock”.

Soon thereafter dramatic aerial pictures, showing that one of the farm’s circular cages was severely buckled, dominated both broadcast and print media coverage. The images made a mockery of the claim advanced in an ingratiating article about the Carradale farm in the local Campbeltown newspaper two months earlier that new “robust anchoring” renders “the pens more stable and better suited to withstand the most extreme weather”.

The damage to the farm allowed some 48,000 large salmon to escape. When it comes to escapes, the Carradale farm has form, having “lost” 16,000 immature fish in 2015. Mowi’s recent record elsewhere in the region is suspect; 73,000 salmon escaped from its farm off Colonsay in January this year. What differentiates this latest escape is the fact that the fish were mature and they entered the wider marine environment just at the time of year when they are predisposed to run into rivers alongside wild salmon

Sure enough, within days large numbers of flabby farmed salmon were showing up in west Scotland rivers, notably in the Firth of Clyde (the Leven) and Ayrshire. These fish dominated rod catches, an indication that they will likely greatly outnumber wild fish on the spawning redds. Mowi’s position statement that it “continues to engage with local and national wild fisheries groups to monitor and assess the presence or absence of salmonid genetic introgression” is essentially meaningless. The genie is well and truly out of the bottle, with farmed salmon of Norwegian origin (alien fish to Scottish rivers) seriously threatening the vital genetic integrity of our already depleted native wild salmon strains. Imagine, if you will, wild wolves interbreeding with poodles and consequently the fitness of the offspring.

It is not currently illegal for a salmon farming company to have an escape in Scotland, so Scottish Government will not intervene. Contrast this with Chile where Mowi has just been fined $6.7 million following a major escape there in 2018.

Indeed, Mowi Scotland is somewhat blasé and on record as recognising that escapes are inevitable (and viewed as just another business expense). In response to the Carradale escape, Ian Roberts, a director at Mowi Scotland, responded thus: "To lose 48,000 fish is extremely disappointing and obviously hits you financially as well... But in the history of salmon farming and... moving into locations that are very high in energy and difficult to farm unfortunately, we have these incidents… it has happened before and it will happen in the future again…."

In these circumstances the only remedy likely to cause Mowi to redouble efforts to retain its stocks within their cages is legal action for damages by District Salmon Fishery Boards and/or their representative body Fisheries Management Scotland (FMS). To date the response by the latter has been muted with no outright condemnation of the escape; they have simply issued advice that the farmed fish should be killed and scale samples taken. Some Boards in the affected area are now looking for FMS to take the lead with robust action.

Considerable numbers of farmed salmon are now also showing up in the rivers of north-west England. There is a growing clamour on the ground for the relevant authorities to instigate appropriate legal action against those responsible. Obviously, no-one can bring a case without the necessary evidence – in this case sample fish. Initially anglers were given the bonkers instruction to release any farmed fish back into the water! Fortunately, this has now been rescinded, at least on the Cumbrian rivers, with the Environment Agency advising that “farmed salmon may be taken and killed” and reported accordingly.


Why a strict ceiling on sea lice must be applied to all Scotland’s salmon farms

Why a strict ceiling on sea lice must be applied to all Scotland’s salmon farms

Wild salmon and sea trout populations in Scotland are dangerously low. For wild salmon and sea trout in the west Highlands and Islands to be properly protected from the negative impact of salmon farming, the effective control of sea lice on farms is a vital first step.

A precautionary approach is essential

S&TCS believes that a genuinely precautionary approach must be applied to the licensing and permitting of any new salmon farms or expansion of existing farms. Such a precautionary approach was also recommended by both the REC and ECCLR Committees in the 2018 Parliamentary Inquiry.

In March 2018, Graeme Dey MSP, Convener of the ECCLR Committee, emphasised the need to apply the precautionary principle to fish farming - “there appears to have been too little focus on the application of the precautionary principle in the development and expansion of the sector…Scotland’s public bodies have a duty to protect biodiversity and this must be to the fore when considering the expansion of the sector. We need to progress on the basis of the precautionary principle …”.

REC Committee (Recommendation 40) was that “although there is a lack of definitive scientific evidence of the various factors that are contributing to the decline of wild salmon stocks, the Committee is nevertheless of the view that a precautionary approach should be taken which will seek to minimise the potential risk to wild salmon stocks wherever possible”.

Put simply, applying the precautionary approach means not using lack of scientific certainty to justify delay in taking action to prevent environmental damage. Where a threat of serious damage has been identified action should be taken to prevent damage occurring. The threat of serious damage to wild salmonids caused by salmon farms has been identified by numerous fisheries scientists, and applying the precautionary principle means putting in place now measures that will prevent salmon farms causing harm to wild salmonids. Waiting to take action until after it has been demonstrated that a particular salmon farm has harmed wild fish is not in accord with the precautionary approach.

In the context of the contested scientific understanding of the negative interactions between farmed and wild fish, fish farm regulation must be underpinned by a robust and strict precautionary approach to protect wild salmonids. Wild salmonid monitoring, particularly in the marine environment, is an imprecise science and is highly unlikely to produce clear and unambiguous results that are not open to multiple different interpretations of what might be occurring.

A strict sea lice ceiling must be applied to all fish farms

Therefore, the precautionary principle demands that adaptive management can only take place under a strict, robust and universally applied sea lice ceiling, in other words an absolute upper limit to the permitted average number of adult female sea lice per farm fish.

Without this ceiling, the burden of proof is effectively reversed, with proof that there is damage being caused to wild salmonids becoming a pre-requisite to any action being taken to address fish farm performance in respect of sea-lice and diseases[1].

 There is already domestic, international and industry support for a strict sea lice ceiling

In November 2018, the Scottish Parliament’s Rural Economy and Connectivity Committee, in its report following its investigations as part of the Inquiry into Salmon Farming, concluded (Recommendation 15) that sea lice triggers should be “challenging” and urged Government to “set a threshold that is comparable with the international industry standards”.

The inter-governmental North Atlantic Salmon Conservation Organization (NASCO) advocates that “100% of farms to have effective sea lice management such that there is no increase in sea lice loads or lice-induced mortality of wild salmonids attributable to the farms”.

In most North Atlantic salmon farming countries statutory on-farm average adult female sea lice limits are set at no more than 0.5 per fish during the critical main wild smolt outward migration period in the spring.

So, why should Scotland’s wild salmon and sea trout be accorded any lesser levels of protection than fish elsewhere?

The Aquaculture Stewardship Council (ASC) certification programme for salmon farming  sets global  standards for salmon farming ( including for sea lice (Requirement 3.1.7) that “farms seeking certification to maintain on-farm lice levels at 0.1 mature female lice during and immediately prior to sensitive periods, particularly outmigration of wild juvenile salmon”. Mowi (formerly Marine Harvest) claims to be working towards “100 % ASC certification” (

So, why should Scotland’s wild salmon and sea trout be accorded aless protection than that recommended by the ASC?

Domestically too, there is support for a strict sea lice ceiling. Scottish Natural Heritage (SNH) has recommended that a strict ceiling for on-farm sea lice levels should be set to protect wild salmonids in the Langavat Special Area for Conservation. In its response to the Screening and Scoping Exercise for the Taranaish fish farm on Loch Roag, SNH required that sea lice control should be based on

a) The ability of the applicant to maintain average sea lice levels in line with our position paper Marine Aquaculture and Wild Salmonids, see Appendix 1:

0.1 adult female lice per fish between February and June inclusive

0.5 adult female lice per fish between July and January inclusive”.

So, why should Scotland’s wild salmon and sea trout now be accorded less protection than that already recommended by Scotland’s statutory nature conservation body?

Adaptive management, by itself, is not enough…

The Salmon Interactions Working Group’s recently published report proposes a system of adaptive management, but without any precautionary underpinning by a strict universally-applied sea lice ceiling.

Under the SIWG proposals, in effect, wild fish interests would have to prove conclusively that damage is being caused to wild salmon and sea trout before sea lice controls on nearby fish farms were tightened.

Adaptive management will be subject to disagreement between fish farmers and regulators over why wild fish had experienced sea lice infestations and it is likely (in the last resort) that there could be legal challenges from the industry.

Experts within Marine Scotland Science and the Crown Estate agree that it would probably take intense monitoring of wild fish for at least three farm production cycles (up to six years) for any pattern of damage to wild fish caused by fish farms to be established, and even then it will likely be the subject of dispute between fish farmers and regulators over the  science.

Therefore, without a strict sea lice ceiling applied to all fish farms from the outset, wild fish would have no more protection from farm-origin sea lice infestation for the foreseeable future. At best, adaptive management alone would, at least for several years, be no more potent in protecting wild fish than the current system. At worst, it will become mired in disputes over what wild fish monitoring is showing and why, leading to no effective control of fish farm production of sea lice.

Why should Scotland’s wild salmon and sea trout be accorded no more effective protection than is currently the case?

 Current Scottish Government sea lice reporting levels are not enough

In a letter to S&TCS (June 2020), Cabinet Secretary Fergus Ewing signalled the Scottish Government’s woeful lack of ambition regarding the control of sea lice on farms. Referring to the current sea policy (which only relates to the health and welfare of the farmed fish), he stated that the intention is to enhance “the sea lice reporting process by reducing intervention levels” (currently 2 and 6 average adult female lice per fish – see Marine Scotland Topic Sheet Number 71 V3) “to 2 and 4 in 2021 – unless there is evidence to the contrary”, forgetting that the industry’s current Code of Good Practice already  has nominal lice treatment advisory thresholds of 0.5 adult lice per fish (February to June) and 1.0 per fish (July to January).

In other words, farms will not even be required to notify the Fish Health Inspectorate (FHI) of sea lice numbers until the average number of female lice per fish reaches 2 at which point, theoretically, FHI is committed to “increased monitoring/surveillance”, although no other sanction is applied. That is a level fully 20 times the ASC limit during wild smolt runs.

Fergus Ewing’s stated objective amounts to confirmation that Scottish Government does not envisage currently that the future system of adaptive management being proposed will be underpinned by a strict universally-applied and precautionary sea lice ceiling.

S&TCS believes that it is imperative that any new regime includes a strict adult female sea lice ceiling applied to all fish farms, which must be rigorously enforced by tough and prompt action, set at 0.5 per farmed fish, dropping to 0.1 during the period of wild smolt emigration, below which ceiling  any adaptive management, based on wild fish monitoring, is then applied.

[1] See, for example, Friends of the Earth Limited, Re Judicial Review [2017] NICA 41

“37. Given the repeated finding that the operations are likely to have significant impact on the environment the decision maker cannot simply put in the balance the absence of evidence of harm…What has been disregarded … is that these operations are considered likely to have significant impact, that the nature and extent of that impact has not been established, that prior to the grant of permission is the requirement to establish that there will be no significant impact and that it is imperative that the precautionary principle be applied.  What must be put in the balance is the absence of evidence that there is no harm. To approach the matter with a requirement for evidence of harm is the negation of the precautionary principle”.