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 (https://www.asc-aqua.org/wp-content/uploads/2019/12/ASC-Salmon-Standard_v1.3_Final.pdf) 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” (https://mowi.com/sustainability/aquaculture-stewardship-council/asc-dashboard/).

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”.

Toxic neonicotinoid washed off salad leaves into protected chalkstream

Toxic neonicotinoid washed off salad leaves into protected chalkstream exceeds acceptable concentrations by up to 400%.

NEWS RELEASE 23 June 2020

Data from a recent Freedom of Information request by Salmon & Trout Conservation shows that levels of Acetamiprid, a pesticide discharged by Bakkavör plc into the Upper Itchen catchment[1], have regularly exceeded acceptable concentrations. This toxic pesticide and many more are washed off leaves in preparing bags of salad.

Bakkavör plc supplies leading retailers, including M&S, Sainsbury's and Waitrose, with fresh produce such as watercress, baby leaf and organic salads and herbs.[2]

Acetamiprid regularly exceeded, by a factor of up to four times, the lethal dose (chronic and acute Regulatory Acceptable Concentration (RAC))[3]. Acetamiprid is in the neonicotinoid family, many of which were recently banned for use in Europe due to their acute toxic impact on bees. While Acetamiprid is considered less harmful to pollinators than its banned relatives, research shows that it is significantly more toxic to aquatic insects.[4]

Nick Measham, CEO Salmon & Trout Conservation said,

“Enough is enough. Bakkavör’s Alresford Salads factory has a long history of polluting the Upper Itchen. This latest revelation is the most troubling yet. Quite simply this pesticide pollution has to stop, and now. These chemicals will be killing aquatic insects, destroying the primary food source of wild salmon and trout. Bakkavör must end emissions of these and all other toxins which occur as a by-product of their processes. If they continue to refuse to do so, the EA must take decisive action.”

S&TC fears this is not the only insecticide discharging from the plant at quantities dangerous to aquatic life, and that, nationally, Bakkavör is not alone in this activity.  Until S&TC raised concerns over potential chemical inputs from the factory affecting the river, no-one was aware or monitoring what was actually being discharged. Current discharge permits require the operators to disclose to the EA any toxic substances which may be present in their discharge, and then monitoring procedures are established accordingly. Clearly, in this case, that did not happen. There are fundamental failures in the regulatory approach applied here, which must be addressed by the EA.

Additional Freedom of Information data obtained by S&TC suggests up to five hundred other sites throughout England of a similar nature could be operating under the same or similar inadequate permits with no pesticide monitoring requirements, but with pesticide residues being discharged.

Dr. Janina Gray, Head of Policy and Science, Salmon & Trout Conservation,

“Bakkavör is surely the tip of the iceberg. These issues appear to be widespread and will be causing ongoing environmental damage. The existing permitting regime wholly fails to protect the environment from the damaging effects of a range of toxic chemicals. What is even more worrying is the emerging science suggesting that a “cocktail effect” may increase the toxicity of many different chemicals beyond the sum of their parts. The EA has failed to keep pace with what is actually polluting our rivers.”

S&TC is calling on Bakkavör plc to stop their discharge immediately until they can be certain they are not discharging pesticides above regulatory standards and until they can demonstrate they are not impacting the river.

Bakkavör plc urgently needs to outline: 

  1. what action it is taking to remove Acetamiprid and other pesticides from its discharge;
  2. why it is taking so long to put proper protections in place for the Itchen;
  3. why as a responsible business, it should be discharging any pesticides into the headwaters of a highly protected chalkstream; and
  4. why, given the growing body of scientific evidence showing synergistic impacts of chemical cocktails, it routinely discharges a cocktail of 40 plus chemicals into the Itchen.

S&TC is calling on the Environment Agency to:

  1. accept no more delays and to vary Bakkavör’s discharge permit immediately, to give the EA the ability to regulate all chemical discharges made by Bakkavör;
  2. enforce permit variations at any other similar activities in England to require monitoring at any sites where pesticides are identified and, given the risk of synergistic effects, limit these discharges to well below safe levels.


(1) Salmon and Trout Conservation

Salmon & Trout Conservation (S&TC) 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 has worked to protect fisheries, fish stocks and the wider aquatic environment for the public benefit. S&TC has charitable status in England, Wales and Scotland 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 salmonid fish stocks and the aquatic environment upon which they depend.


2) Case History 

Fears about pesticides and other chemicals in the discharges from this salad washing plant have been long standing[5] and culminated in June 2018 when S&TC issued the EA with a formal notification of environmental damage pursuant to the Environmental Liability Directive. This followed the results of S&TC’s invertebrate sampling[6] at a site immediately downstream of Bakkavör’s outflows which indicated that chemicals were impacting the invertebrate communities.

The resulting EA investigation confirmed S&TC’s findings; that there were pesticides present, which were on the salad leaves imported by Bakkavör and which were being subsequently washed off and into the Upper Itchen. It appears that Bakkavör had not self-notified the EA of the presence of these chemicals. Once made aware of the pesticide threat the EA began a monitoring and sampling regime. This testing revealed the presence of dozens of chemicals, pesticides and herbicides being washed off the fresh produce at Bakkavör Alresford Salads.


[1] The salad washing plant is situated on the River Aire a tributary of the protected River Itchen, a Special Area of Conservation (SAC)

[2] https://www.bakkavor.com/investors/

[3] The long-term chronic Regulatory Acceptable Concentration (RAC) for Acetamiprid is 0.0235mg/l, and the short- term acute RAC is 0.085mg/l.

[4] https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/11.htm

[5] https://www.salmon-trout.org/2019/06/17/bakkavor-alresford-salads-impacting-upper-itchen/ [6] http://bit.ly/2RhzimT

Appendices (3):

Graph 1: Presence of Acetamiprid in the overnight wash discharge of Bakkavör Alresford Salads. The Lowest Limit of Analytical Determination (LOD) refers to the lowest concentration of the analyte that can be reliably detected and quantified. [It is believed that salad leaves associated with Acetamiprid, and its use, are more commonly associated with Spring seasonal produce, hence the absence of data during other months].

Table 1: Results of the sampling of the water leaving the factory during the overnight wash of salads and other fresh produce. [Only certain laboratories have the ability to test for Acetamiprid at the levels at which it is found to cause harm].

Table 2: Monthly Bakkavor - April 2020 - Sampling Data Summary April 2020. Released as part of Environment Agency FOI: 200605 SSD171346 - Bakkavor Data


S&TC Cymru Update June 2020

Richard Garner Williams, S&TC National Office for Wales writes:

In a spirited demonstration of enthusiastic collaboration S&TC Cymru, the Wild Trout Trust, the Grayling Society and the Game and Wildlife Trust recently joined forces in writing to Lesley Griffiths, Welsh Government Minister for Environment, Energy and Rural Affairs offering broad support for Natural Resources Wales’ Salmon and Sea Trout Plan of Action. The Plan was launched at the Minister’s request in response to the outcome of the Local Inquiry on Natural Resources Wales’ proposed All Wales Salmon and Sea Trout Byelaws earlier this year. We understand the Plan of Action will be underlain by a detailed Forward Delivery Plan which all four organisations look forward to examining and discussing upon publication. The letter also urged the Minister to ensure that the implementation of the Plan be adequately funded to ensure that Wales meets its national and international obligations towards these two keystone species.

Agricultural pollution continues to wreak havoc on the fragile populations of the wild fish of Wales with a recent slurry containment failure killing fish along at least 4km of the Afon Peris, near Llanon on the Cardigan Bay coast. It must be presumed the invertebrate population within the affected reaches fared little better than the fish, further compounding the effects of the spill on the river’s biodiversity. Although diminutive in size, S&TC Cymru is becoming increasingly convinced that rivers such as the Peris play an important role in sewin stock recruitment, with emerging smolts supplementing returning numbers of mature fish in larger, neighbouring rivers. With the Teifi to the south and the Rheidol, Dyfi and Mawddach to the north, we can only begin to wonder what the long term, more distant impacts of the spill might be. Regrettably, the incident was only brought to the attention of the authorities when members of the public noticed dead fish floating in the polluted water. It would appear that the farmer was unaware of the incident until alerted to it by NRW. Equipment or storage failures such as this are a far too frequent an event and suggest widespread negligence and lack of investment in the infrastructure required for today’s more intensive methods of dairy production. S&TC Cymru have repeatedly called on Welsh Government to address these issues and while the recently announced Draft Water Resources Regulations give some hope for improvement in the control of agricultural pollution, we have yet to see evidence of the commitment to the extra resources required for their enforcement.

Originally planned for introduction in January of this year, the new agricultural regulations designed to tackle the scourge of agricultural pollution remain in limbo as Welsh Government addresses the issues posed by Covid-19. S&TC Cymru wrote to congratulate the Minister on her original forthright announcement of the need to take action but have since become increasingly concerned at hints of mission creep. During the latter months of last year, at the behest of the Minister, Natural Resources Wales and NFU Cymru collaborated on a project to explore potential voluntary options, suggesting a more flexible approach based on “earned autonomy” which would release individuals from strict regulatory control. Unlike Scotland and England, where the impact of agriculture on water is regulated by statutory basic rules, Wales has no such general binding measures, relying instead on voluntary compliance with guidelines laid put in the Code of Good Agricultural Practice (CoGAP). Patently, this has failed, as the regular reports of both acute and chronic incidents of pollution make clear. We therefore conclude there can be no further place for the provision of voluntary measures with regard to the impact of agriculture on the freshwater environment if Welsh Government is serious in its intent to conclusively address the matter. With that in mind and again in the spirit of collaboration and cooperation, the Grayling Society and the Wild Trout Trust recently joined with S&TC Cymru as co-signatories to a letter to the Minister calling for the introduction of a suite of basic rules for water for all land users across the whole of Wales, in advance of the currently proposed regulations, whatever their final form. I look forward to reporting, hopefully, a positive outcome to this and thank the WTT and the GS for their ready participation in our collaborative approach.

Finally, I’m sure you were all as disappointed as was I that we had to postpone our spring seminar. This has become an extremely popular event and this year’s bookings were already close to capacity when we suddenly found ourselves overtaken by events. With so much uncertainty continuing to surround the resumption of normal social interactions we have decided to formally cancel our 2020 seminar and start instead to prepare for the 2021 event. Until then, thank you for your valued support and please feel free to get in touch at any time should you wish to discuss matters in greater detail.

Reporting with a purpose

S&TC is a national organisation and we use evidence from local case studies to help instigate policy changes that will benefit UK wild fish populations. But, this is just part of the value - we are making all our Riverfly Census findings available so they can be used to inform local management and drive action.

Each individual river report is based on three years of surveying data. Where possible, we have linked up our findings with other existing literature and data. Using the available information we suggest where local fishing and/or conservation groups can focus their management efforts to achieve the best health outcomes for each of the 12 original Census rivers.

Some of our local reports can be found on the slider below. Alternatively, visit the Riverfly Census page and scroll down to the map.

SmartRivers launched in Wales

S&TC Cymru launches its first SmartRivers hub in partnership with the South East Wales Rivers Trust

S&TC Cymru is delighted to announce that South East Wales Rivers Trust (SEWRT) is to host the first SmartRivers hub in Wales. The hub is certain to play a valuable role in assisting SEWRT restore the natural beauty and biodiversity of the postindustrial Cynon.

SmartRivers, born out of the Riverfly Census, uses aquatic invertebrates as a diagnostic test to tell us about the health of rivers and possible pollutants affecting wild fish populations.

Quick and easy to deploy, but also producing robust and powerful information, polluters of rivers and streams have already been forced to take action. "SmartRivers Delivering Results"

Richard Garner Williams, S&TC National Office for Wales

"I'm delighted SEWRT has chosen to engage with S&TC's SmartRivers programme and look forward to seeing the positive contribution the hub will make towards the Trust's ambitions. It is heartwarming to see the rivers of the south Wales valleys returning to life and I wish the all those associated with the Trust great success in their endeavours." 

river cynon smartrivers

SmartRivers provides valuable information to assist with catchment management decisions, as well as establishing an insurance policy for rivers in the form of a benchmark of their health.

The South East Wales Rivers Trust (SEWRT) was formed in 2007 to recover river habitats in the former industrial valleys of South Wales. The valley environment suffered a great deal in the industrial era, but is slowly recovering, although weirs, contemporary industrial pollution and waste water issues continue to present problems for fish habitats and migration. Thanks to European funding, SEWRT has spent in excess of£190,0000 over recent years on twenty fish easements and three habitat improvement schemes opening up an additional one hundred and thirteen kilometres of river to migrating fish. Regrettably, due to pressure of work, the Cynon did not feature heavily in the programme, benefitting from only five minor easements.  Historically, the Cynon valley was a major area of coal production and heavy industry, the consequences of which had a devastating impact on the ecology of the river. However, the very upper reaches were not so badly affected and over the years these have proved to be the areas from which life has returned to repopulate this bruised and battered river. Local interest in the recovery and importance of the Cynon has generated an enthusiastic band of volunteers, ready and willing to carry out much of the work. The driving force within SEWRT is working with the local community to value the river, carry out community river surveys and run river restoration and fly monitoring courses.

Tony Rees, Chairperson of the SEWRT said:

“As Chairman of the SEWRT I have been heavily involved in several fly monitoring programmes.  Reading about the SmartRivers project made me realise how well this would fit into a new project that SEWRT is running on a truly urban river, the Cynon. I already have funding for two fly monitoring courses locally as well as to run a river restoration course. Using SmartRivers will raise the standard of the work we will be doing to a higher level and is a perfect fit for the “River for All” project on the Cynon. It will ultimately help us to understand in greater depth the problems in our valley rivers. It will also be an excellent way to show those who join in with us the unseen life in the river that is so important to all our wellbeing, but that the public has little knowledge of.  We are grateful to Welsh Water, Pen Y Cymoedd wind farm community fund, Natural Resources Wales and Post Code Lottery for supporting the project.”

SmartRivers includes a comprehensive online and field-based training scheme, 1-2-1 support and good use of information technology, including a dedicated S&TC Invert ID App. This ensures that local community groups themselves are able to monitor the water quality in their rivers to a near-professional standard.

Lauren Mattingley, SmartRivers Project Manager S&TC

We are delighted to be continuing our water quality work in Wales through SmartRivers. The Cynon is unlike any river we have enrolled in the programme to date, so the information we will obtain through the monitoring will be fascinating. It is astounding that tiny invertebrates can give us such vast insight into the subtle, and often invisible, pressures our young fish are being exposed to. We are very excited to educate the Cynon volunteers on these pressures. SmartRivers will give them the scientific power to understand what improvements are needed and measure the biological impact of any actions they may take.”

 Nick Measham, S&TC CEO said:

“The rivers of Wales rivers suffered so much in the industrial era and sadly continue to face a lot of pressure. We are always pleased to hear about the positive work being done and some good news stories about river restoration. SEWRT have achieved so much good for the rivers under their care. We hope our SmartRivers programme will help SEWRT turn high quality citizen science into meaningful real-world action that here and now improves outcomes for wild fish and the wider habitat.”

Dennis Baynham, Secretary of the SEWRT

“The Cynon starts above Hirwaun and runs down the valley through the middle of Aberdare and Mountain Ash joining the Taff in Abercynon. It is a truly urban river in need of some TLC. It suffered years of pollution from colliery waste and the Phurnacite plant in Abercwmboi, but in the years since they stopped production water quality has improved tremendously. It now suffers with water quality problems from sewerage over flows and poor connections. I welcome this initiative as a step in the direction of identifying all the problems the Cynon. The local angling fraternity are behind this.”

 Afon Cynon, A River for all: Gareth Edge Project officer

“My project aims to improve the biodiversity of the Cynon through meaningful education, community engagement and small-scale environmental improvements. Volunteers are encouraged to undertake a Level 1 accredited qualification in River Restoration. Partner Schools look after critically endangered European eels for release on the catchment, as part of a Europe wide restocking project. River clean-ups are undertaken in partnership with Keep Wales Tidy. Invasive species will also be managed with the aid of local authority. Partnering S&TC and the SmartRivers programme will enable me to take my work to a wider audience of volunteers.”

 Natural Resources Wales issued the following statement,

“NRW is keen to support initiatives like SmartRivers, that involve communities in citizen science, and engender a wider and increased understanding of river ecosystems. SmartRivers monitoring aims to pick up issues, and working together, we can better protect and improve our river environments.”

 For more information about SmartRivers and how it could support your river management activities, please email: smartrivers@salmon-trout.org

 For more information on the work of S&TC Cymru, please email our National Officer for Wales, Richard Garner Williams: wales@salmon-trout.org

Please note: We can only run courses with groups of around 10 volunteers and not for individuals. However, if you are struggling to establish a 'hub' group your local Rivers Trust or Wildlife Trust may be able to help.


Reporting with a purpose

S&TC is a national organisation and we use evidence from local case studies to help instigate policy changes that will benefit UK wild fish populations. But, this is just part of the value - we are making all our Riverfly Census findings available so they can be used to inform local management and drive action.

Each individual river report is based on three years of surveying data. Where possible, we have linked up our findings with other existing literature and data. Using the available information we suggest where local fishing and/or conservation groups can focus their management efforts to achieve the best health outcomes for each of the 12 original Census rivers.

Some of our local reports can be found on the slider below. Alternatively, visit the Riverfly Census page and scroll down to the map.

NASCO 2020

Paul Knight reports on the 37th Annual Meeting of NASCO

The North Atlantic Salmon Conservation Organisation (NASCO) met for its Annual Meeting in the first week of June, although this year, uniquely, all the meetings were held virtually by video link, with those not directly involved being able to listen in by phone.  Despite concerns that such a large international conference would be difficult to organise and run – it involved a Council and three separate Commissions – it actually went very smoothly, albeit with some of the more important issues, particularly from an NGO viewpoint, being postponed until Council is able to meet face-to-face, hopefully this autumn.

The main objective for the NGOs was to influence support for a full day Theme-based Special Session (TBSS) on salmon farming at next year’s Annual meeting.  This follows increasing concern right across the north Atlantic – and also the Pacific – that open-net salmon farming is the most damaging issue for wild salmon and sea trout that NASCO parties and jurisdictions actually have the power to do something about.  The NGOs were therefore delighted to receive unanimous support from all the Heads of Delegation for the TBSS in June next year, even agreeing to extending the meeting by a day if that is needed to accommodate the event.

The main concern driving the NGOs is that, despite NASCO resolutions going back at least 17 years, and a Council direction that open-net salmon farming should receive particular attention from relevant countries, the Implementation Plan process – the 5-year plans for salmon conservation put forward by each party and jurisdiction – clearly show a failure to protect wild fish from the adverse impacts of sea lice infestations killing migrating smolts, and escaped farmed fish interbreeding with natural salmon populations.  Two countries with significant salmon farming industries openly admit that they have no action to regulate sea lice emanating from open pen farms, while another has a national policy allowing 30% of wild salmon smolts to be killed before any serious regulation is considered.

So, the TBSS is a small but significant step along a very long road needed to turn around the juggernaut of political commitment so that appropriately effective regulations are introduced (in those jurisdictions where they are still absent) and are enforced rigorously to protect wild fish.  It is a sad admission that no country with both a salmon farming industry and wild salmon populations presently protect their natural fish stocks adequately enough.

Another pleasing aspect of this meeting was that, following several incidents last year when the NGOs felt they were being kept at arms’ length from important Council decisions, there were signs that our complaints had been taken onboard.  However, there are still serious issues to address for the NGOs at the autumn intersessional Council meeting, including:

  • The process for completing and reviewing the Implementation Plans – we want to see far more genuine commitment in these plans to protecting wild salmon, particularly from the harmful effects of salmon farming
  • An opportunity for NGOs to input fully to the upcoming external performance review, which will be an independent audit of NASCO’s performance since the previous review in 2012 in achieving its primary objective of protecting wild salmon.
  • Confirmation that NASCO is committed to a fully transparent process in all its work, including NGO access to and involvement in all Council and Commission decisions
  • Through our representation on the Implementation Plan and Annual Progress Report Review Group, NGO involvement in developing TBSSs for upcoming annual meetings
  • Following on the success of this virtual meeting, how much of NASCO’s work could be delivered in this way in future, so cutting down time and money resources in attending meetings, particularly those outside of the main annual event, which we agree should remain face-to-face under normal circumstances

In summary, therefore, a useful meeting where the NGOs achieved our main goal of a TBSS on salmon farming next year.  Much still to do and agree, and we now look forward to the face-to-face intersessional Council meeting in the autumn – provided we are able to travel again by then, of course.

Salmon farmers own data makes the case for much lower sea lice limits

Corin Smith writes,

"Contrary to what you may believe salmon farmers go to great lengths to protect Atlantic salmon smolts from the harm caused by sea lice. The problem is they only protect the smolts inside the salmon farms, not the wild ones on the outside."

 Analysis combining multiple industry and government datasets reveals the low levels at which salmon farmers can, and do, successfully maintain sea lice to protect farmed salmon smolts.

The insight that follows comes with the following explanations and caveats.

Datasets from SEPA, Marine Scotland, Fish Health Inspectorate, Crown Estate Scotland and the Scottish Salmon Producers Organisation were all combined into a single proprietary database. The data covered the period 2018 and 2019. However, it is the case that all of the data is collected and reported by the salmon farming industry itself. There is no independent body which collects, verifies or audits any of the data. There is a lack of transparency with regard to operational methodologies, and therefore consistency of, sea lice count data. Where averages are used by the industry there is no transparency as to how these are derived. There is no information as to how any of these processes may have varied over time. The view we have of the industry is the one it currently permits us to see.

Sea lice counts are recorded by salmon farmers as often as daily and often at the individual pen level. This data is retained within the salmon farming corporations and extends back a period of perhaps decades in some cases.

Where average weekly sea lice numbers on salmon farms in Scotland breach thresholds outlined in The Regulation of Sea Lice in Scotland policy document, (currently 2.0 and 6.0 per farmed salmon and which refers only to a single life stage, gravid females, of a single species “Lepeophtheirus salmonis”)  sea lice counts are reported to Marine Scotland. These reports are therefore sporadic, short lived and of little use for any form of regression analysis.

The Scottish Salmon Producers Organisation also receives sea lice count information from salmon farmers and publishes monthly sea lice averages for each salmon farm in Scotland. The mathematical basis for how the SSPO derives its averages is not published. The SSPO has been publishing this individual farm data since Jan 2018. The effect of using “averages of averages” is to remove a lot of potential volatility in the data.

By way of example Vacasay salmon farm in Loch Roag, reported to Marine Scotland the following weekly sea lice count data:

Week 23: 0, Week 24: “no data”, Week 25: 7.28, Week 26: 24.22

The SSPO monthly average recorded this as: 4.69

There are reasonable explanations for this seemingly implausible mathematical outcome, which reflect the possible use of weighted averages. Analysis of averages alone can be useful for deriving insight, but caution should be noted that they do not, apparently, account for any changes in scale. For example, two salmon farms may have the same average sea lice count, but one may be twice the size of the other. Analysis of absolute emissions is fundamental in assessing risk to wild fish populations. Absolute production/emission of sea lice from salmon farms is a function of an average sea lice number per fish and numbers of fish. Numbers of fish on salmon farms is not a figure which is recorded or reported in any publicly accessible dataset. The resulting abundance and location of salmon farm derived sea lice external to the farm is further dependent on a number of other factors including temperature, salinity, weather conditions and geography.

Clearly there are pros and cons to using a monthly “average of averages” approach, which depend on the intended purpose of the data. However, some useful insight can be derived, especially given the continuity of the dataset in comparison to anything else available. Hence, SSPO data forms the basis of the following insight.

The original proposition was that salmon farms do, in fact, maintain sea lice numbers at low levels, but only when farmed salmon smolts are present. It should be noted that a farmed salmon smolt may be 100gms or considerably larger. Wild salmon smolts are more likely to be between 50-80gms.

Even at lower levels, sea lice on smolts will result in lethal, and perhaps more significantly, sub lethal effects which impact the fish throughout the remainder of its life. In the case of farmed salmon, the effects of sea lice infestations may reduce growth rates and feed conversion, resulting in smaller more expensive to produce salmon. In wild smolts it may reduce the ability of the fish to survive migration, grow at the rate required to catch prey and/or impact fecundity. The immediate lethal effects of sea lice infestation on a smolt varies directly with its size.

The chart below (sea_lice_vs_length_production_cycle) plots the average sea lice count for all farms, for all months in 2018/19, against the stage of the production cycle the count was recorded. A straight average is used.

The simplest interpretation of this data is that sea lice levels are, in fact, effectively maintained at much lower levels in the early stages of a farmed salmon’s life in sea water than in later stages. Further, that there is a strong correlation between rising sea lice levels on salmon farms and the length of time fish have been in the sea water. It is of course the case that the longer a fish spends in sea water, the larger it will get. Length of production cycle is in effect a proxy for fish weight, a data point which is not publicly available.


For reference, seasonality of sea lice numbers on salmon farms was also examined. This showed a slight seasonal effect where sea lice levels were higher in September and October. Seasonal effects may be the result of environmental factors; sea temperatures are at their highest in these months and so sea lice reproduce more rapidly. However, it could also be influenced by operational reasons such as larger numbers of farms reaching maturity at this time, relative to other months, in preparation for seasonal trends associated with smoked salmon and Christmas. It is, however, clear that from a statistical perspective that correlation with stage of production cycle is by far and away the dominant factor in sea lice abundance on salmon farms.


The table below, shows us that the vast majority of salmon farms managed to maintain monthly average sea lice levels below 0.5 sea lice per farmed salmon for the first twelve months of the production cycle.

Less than 13

Out of a total of 2351 published counts for farms reporting their sea lice levels in the first twelve months of production, 1751 (74%) were at or below 0.5 sea lice per farmed salmon.

The outliers, particularly the figure of 16.68 reflect the fact that from time to time salmon farmers will transfer mature salmon from one farm, to an empty farm elsewhere, for fish health reasons. In the data this is recorded as being Month 1 of the production cycle. This issue occurs in a tiny number of cases.

It would clearly be helpful if salmon farming data indicated information such as fish numbers, fish weight and stage of production/lifecycle.

The chart below shows the same information.


Growth rates and stocking size of farmed salmon smolts in seawater varies according to different strategies used by the operator. However, assuming a smolt is stocked at 100gms, roughly six to nine months later it will weigh around 1kg. The same size as a small wild grilse on the west coast of Scotland.

On average, we see that salmon farmers maintain sea lice levels at 0.2 sea lice per farmed salmon for the first two months of the sea water phase, when the farmed smolt will grow on from 100gms. This rises to 0.4 in month 4 and by month 10, once the smolt has grown on to approximately 1kg, the average sea lice level has been allowed to more than triple, to 0.7 sea lice per farmed salmon.

When one examines the raw data for the first twelve months of the sea water phase it is the case that there is low degree of volatility in the counts from month to month on individual farms, and also when compared to farms across all operators. This would indicate a relatively high degree of control is being exerted on sea lice numbers by salmon farm operators.

When one introduces data from SEPA’s databases relating to the use of the two main chemicals used to prevent sea lice on salmon farms, a striking picture emerges.


Prima facie it could be said that where salmon farmers use chemicals to prevent sea lice occurring, they do so predominantly in the first twelve months of the production cycle. One could argue this is when smolts would be most adversely affected by sea lice and therefore have the greatest commercial impact on a salmon farm. Every sea louse on a farmed smolt reduces the profit that will be made from it as an adult, as a result of reduced health and growth performance for the rest of its life. As the fish increase in size the sea lice carrying capacity steadily increases. The apparent need for preventative chemical measures declines. As farmed salmon increase in size and age, so the financial impact of higher sea lice numbers declines. To the point where at the end of the production cycle the impacts of very high numbers of salmon farm sea lice on the commercial value of a farmed salmon are negligible, and likely far outweighed by the cost of maintaining them at the low levels present in the early stages of production.

That is of course a simple interpretation. The apparent lack of chemical use in later stages may reflect a transition to well-boat based sea lice strategies (physical and chemical) which can begin to be deployed once the farmed salmon are larger. Well-boat chemical use is not recorded in SEPA’s data set. However, it remains the case that any treatment strategies deployed demonstrably do not maintain sea lice numbers at the low levels that were achieved in the early stages of production.

One issue worth noting is an emerging trend toward stocking farmed smolts at much larger sizes, having been grown on in land-based facilities, which for obvious reasons have no sea lice issues. The rationale for the operator is clear. Doing so effectively eliminates the first year in sea water, a period that clearly requires expensive early stage chemical prophylactics. This strategy, however, presents a new and serious long-term risk for wild salmonids. Much of the discourse about sea lice impacts from salmon farms relates to shocking peak sea lice counts. While damaging and troubling these are relatively isolated.

The table below shows the frequency of monthly sea lice counts for all salmon farms, for all months in 2018 and 2019, aggregated by ranges. One can clearly see the vast majority of sea lice occurrence takes place in the lower ranges.


It is the ever-present background level of sea lice being emitted from salmon farms that should be of most concern in terms of wild fish conservation.

By effectively removing the first twelve months of the production cycle, all salmon farm production in Scotland would be late cycle all of the time, where much higher levels of sea lice are historically present on salmon farms. If 1kg smolts were stocked on salmon farms and salmon farmers adopted the same tolerable sea lice level strategy shown in the first chart, this would raise the average sea lice floor levels on salmon farms from 0.5 usually seen in the first twelve months, where wild fish have some hope of respite, to a new minimum average of 1.1. This could in effect more than double the minimum background sea lice levels present on salmon farms and being emitted into the environment.

Of course, the farmed fish would be in the water for less time, but this in no way changes the dynamics of sea lice ingress, incubation, proliferation and emission from open cage salmon farms in the late stages of production. Sea lice levels are, after all, a business decision. There’s no indication that salmon farmers would willingly commit additional capital and operational expenditure to reduce late cycle sea lice levels on salmon farms, below that which occurs now. While a shorter seawater phase would potentially benefit the salmon farming business model, it simply means the next batch of bigger farmed salmon arrive earlier in the sea, resulting in a greater constant intensity of salmon farm production.

On this basis shorter production cycles may be dramatically worse for wild salmon, and sea trout in particular, whose lifecycle is often entirely contained in a single location. This is an area which merits considerable investigation to quantify the risks to wild salmonids that a super-size smolt stocking policy on salmon farms could represent.

The Norwegian, Canadian and Faroese corporations that own 99% of salmon farms in Scotland see their potential profit in every farmed smolt. They recognise the harm that salmon farm sea lice will inflict on farmed smolts, and their profits, and so they go to great lengths and expense to protect their investment. It is unconscionable that salmon farmers do not accept an obligation to offer the same protection to Scotland’s wild Atlantic salmon smolts, from the same harm caused by the very same salmon farm sea lice, simply because they are on the other side of a net a few millimetres wide.

Corin Smith was previously commercial operations director at betfair.com with responsibility for insight and optimisation. Latterly establishing a data analysis consultancy serving FTSE and NASDAQ listed clients. He now consults for S&TC on communications and strategy.

The SAMARCH Project International Salmonid Coastal and Marine Telemetry Workshop


The "Blue Book"

Based on a workshop organised by Salmon & Trout Conservation and Game & Wildlife Conservation Trust on behalf of the SAMARCH Project and the Atlantic Salmon Trust in Southampton, UK, on the 5th and 6th November 2019.

SAMARCH is a five-year project with a grant of €5.8m from the EU’s France Channel England Interreg Channel programme.

Download HERE

Salmon Farm Regulation: S&TC initial response to SIWG report

Report fails to advocate the simple regulatory system urgently required to protect wild fish including adherence to the precautionary principle

Initial response to the Salmon Interactions Working Group (SIWG) Report

 Salmon and Trout Conservation Scotland                                                               5 May 2020

On May 1st, the Scottish Government released the “Report of the Salmon Interactions Working Group”. The Group’s terms of reference relate specifically and only to the interactions between farmed salmon and farmed trout and wild salmon and sea trout.

The Report contains 42 recommendations. It concludes that there should be a single body responsible for operating a regulatory system to protect wild salmonids from the effects of fish farms, and it concludes that the regulatory system should be robust, transparent, enforceable and enforced. Unfortunately, the regulatory system outlined by the Report would not achieve that aim.

Burden of proof reversed:

In particular the regulatory system proposed by SIWG lacks any adherence to a precautionary approach to wild salmon and sea trout protection, i.e. that the absence of absolute scientific evidence should not stand in the way of effective management or regulation when damage to wild fish is suspected.

The report recommends that those seeking to protect wild salmon and sea trout will have to prove damage is being caused before any action is taken to regulate poor performance at fish farms. This is quite contrary to the precautionary approach.  It is completely at odds with the Scottish Government’s existing and long-term commitment to the precautionary principle[1] and its legal duty to further nature conservation (including both wild salmon and sea trout)[2]. It also fails to follow the recommendations of both Parliamentary Committees who reported in 2018 that the precautionary approach should be adopted.

A robust and strict precautionary approach is vital to underpin an effective regulatory system. The SIWG envisages the burden of proof being reversed, so that establishing proof that there is damage being caused to wild fish, particularly by sea lice, is to be a pre-requisite to any action being taken by the salmon farm(s). The object should be to act promptly to prevent damage. Monitoring of wild fish in the marine environment is far from an exact science. Reversing the burden of proof will inevitably lead to delay, disputes and legal challenges by salmon farmers determined to maintain or increase production.

Financial support no substitute:

We are concerned that The SIWG report does not just deal with the interactions between farms and wild salmonids. Financial support for research and other conservation work is urgently required but it cannot be considered a substitute for an effective system of regulation.


There are a number of serious omissions from the recommendations, for example:

  • There are no robust maximum on-farm sea lice levels proposed or even envisaged by SIWG that would apply to all farms as a ceiling above which sea lice levels on-farm must not be allowed to rise. This omission is completely at odd with international norms.
  • There is no requirement for the publication in near real time of individual farm sea lice data.
  • There is no requirement for independent monitoring.
  • There are no proposals for effective public scrutiny and monitoring of farm management.

SIWG REPORT:  https://bit.ly/SIWG_report

We will soon be publishing a detailed response to the SIWG Report.

[1] The environmental principles by which the Scottish Government must abide are enshrined in Article 191(2) of Treaty on the Functioning of the European Union FEU, originally the Treaty of Rome. The principles include the precautionary principle, which states that where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

[2] Section 1, Nature Conservation (Scotland) Act 2004


Increase in abundance: A dangerously simplistic view of river health

Species richness and assemblage gives a far more accurate assessment of invertebrate communities………..

Dr Janina Gray, Head of Science & Environmental Policy, responds to a recent article in The Times,

Your article Boom in freshwater bugs bucks trend of disappearing insects (April 24th) sets a dangerously simplistic view of the health of our rivers and water life.

The article reports only one metric – increase in abundance – and not the diversity of species present. Species richness and assemblage gives a far more accurate assessment of invertebrate communities and consequently a river’s health.  For instance, our work has shown that chironomid species can have very high abundances, but they are an indicator of poor water quality, and so their abundance/biomass should not be applauded.

Using abundance data is not a metric which can be used to infer ‘bugs are not disappearing’. S&TC’s Riverfly Census, which recorded 34,000 insects from 480 species across 12 English rivers, showed that pesticides, sediment and excess phosphate are adversely impacting all our rivers to some extent, and are especially damaging to our chalkstreams – once the byword for pristine water quality.  We therefore strongly suspect that your article reports false positives on the true state of freshwater biodiversity and health, by inferring an increase in abundance of pollution-tolerant bugs is a good thing. In order to understand the true state of freshwater bugs, studies must use species richness and abundance data together to form an accurate assessment.

Reporting with a purpose

S&TC is a national organisation and we use evidence from local case studies to help instigate policy changes that will benefit UK wild fish populations. But, this is just part of the value - we are making all our Riverfly Census findings available so they can be used to inform local management and drive action.

Each individual river report is based on three years of surveying data. Where possible, we have linked up our findings with other existing literature and data. Using the available information we suggest where local fishing and/or conservation groups can focus their management efforts to achieve the best health outcomes for each of the 12 original Census rivers.

Some of our local reports can be found on the slider below. Alternatively, visit the Riverfly Census page and scroll down to the map.

Milk. A serious environmental threat?

So, here’s the shocking news about the potential of milk to pollute rivers.

Paul Knight, S&TC CEO writes,

One of the consequences of the coronavirus pandemic has been that the demand for milk has slumped and so dairy farmers have had to pour away their excess, cows still have to be milked, after all, so production cannot just stop.  In Wales, home of the new crop of mega dairy units, the rules state that unwanted milk should be poured into slurry storage if possible, and only sprayed onto fields if absolutely necessary.

Slurry from diary units is a consistent polluter of our rivers. It is sprayed onto fields and the first decent rain shower takes it straight into the nearest watercourse as run-off.  We have heard reports some farmers even dispose of slurry directly into rivers, often at night in an attempt to hide their nefarious activity. The results can be devastating for local fish stocks, because of oxygen depletion due to the micro-organisms feeding on the organic material in slurry.

So, here’s the shocking news about the potential of milk to pollute rivers.  Take treated human sewage as our baseline. A biological oxygen demand (BOD) of up to 60 mg of oxygen per litre of pollutant.  From this, these impacts have the following BOD:

No-one is yet suggesting that milk is finding its way into rivers, but the purpose of the above table is to show just how potentially polluting these agricultural waste products can be if they enter water courses. It is not so much that they are directly toxic to fish and water life, it is that they extract the oxygen out of the system to the extent that, in serious cases, all affected life will die as a consequence.

This is why S&TC is demanding government agencies are properly resourced to monitor watercourses effectively and enforce existing legislation.  We have the legislation, we just need the political will and funding to deal with those farmers who continue to pollute our rivers and damage wild fish stocks.

We are also determined to influence post-Brexit agricultural policies that incentivise farmers to invest in such infrastructure as new storage facilities for slurry or silage that don’t leak. But, while we lobby for these incentives to help farmers, we need the existing laws and regulations to be enforced. We are being fair to fish, not unfair to farmers.