Sea-lice at Scottish salmon farms run by Sainsbury’s supplier yet again threatening west coast wild salmon and sea trout

Challenge to supermarket to replace earlier ‘warm words’ with robust action

S&TCS calls on Sainsbury's to refuse to accept farmed fish from sea-lice infested farms and to support the S&TCS campaign to change the law to protect wild salmon and sea trout

Salmon & Trout Conservation Scotland (S&TCS) has again had to take Sainsbury's to task for stocking on its shelves salmon from Scottish salmon farms where sea lice infestation threatens wild salmon and sea trout.

A year ago, when challenged by S&TCS, Sainsbury's acknowledged that the sea lice levels had risen to unprecedented levels on some of its supplier's farms threatening wild salmon and sea trout with lethal infestation of these parasites – "scenarios such as that experienced in the Long Long and Croe management area in 2014 must be avoided in future". Sainsbury's stated that it was "confident that this can be delivered through improved monitoring and development of a wider suite of control solutions thus reducing reliance on a relatively small number of medicines". Sainsbury's also reaffirmed to S&TCS its "overarching target of rearing salmon in the seawater growth phase which are free from mobile life stages of salmon lice".

Andrew Graham-Stewart, Director of S&TCS, said:

"As part of S&TCS' campaign to highlight the threat to wild salmon and sea trout from the huge numbers of parasites breeding on Scottish fish-farm, we have asked Britain's leading supermarkets to examine critically their suppliers' record and reconsider whether they should continue to sell farmed salmon from companies that operate fish-farms highlighted in the S&TCS Report (see note 2) as being in regions of Scotland that have failed to secure proper control of sea lice.

We spoke to Sainsbury's in late 2014 and 2015 and received all sorts of reassurances, but their supplier's farms are still causing serious concern. We don't want any more 'warm words', we need action. If its assurances a year ago are to be taken seriously, we believe Sainsbury's must now refuse to take fish from farms if sea lice numbers have gone over and stayed over the industry's Code of Good Practice (CoGP) thresholds for sea lice for any length of time".

The most recent sea lice figures for the Loch Long and Croe management areas (covering Sainsbury's supplier Marine Harvest's farms at Loch Duich, Loch Alsh and Ardintoul) show lice numbers have again, in late 2015, gone over the CoGP adult female sea-lice thresholds, as the biomass of farmed fish on the farms has risen. By December 2015, the levels were already nearly seven times the threshold (on average reaching 6.78 adult female sea lice per farmed fish).

Contrast this to what Sainsbury's had said last year, that its supplier, Marine Harvest had committed to adopting a target of 0.1 mature female lice per fish duration sensitive periods for wild fish on certified farms, with Sainsbury's adopting a 'target' for zero presence of such life stages during the entire seawater phase.

The most recent lice problem occurred despite Marine Harvest using chemical treatments for sea lice on its farms. During the last three months of 2015, the three farms concerned have treated for sea-lice eight times, using azamethiphos and deltamethrin, but this has not solved the lice problem.

Sainsbury's had also placed great emphasis on the use of cleaner fish – "the use of cleaner fish is undoubtedly the method which is receiving most attention at present as this has been proven as an effective control in recent years" – and told S&TCS that Marine Harvest had confirmed that all marine farms would be stocked with adequate levels of cleaner fish in 2015; S&TCS remains unconvinced that cleaner fish are a panacea.

However, on 29th July 2015, Loch Alsh was inspected by the Fish Health Inspectorate (FHI) and no cleaner fish were on site, with FHI reporting that the farm "might get wrasse or lumpsuckers, not aware of specific plans. No cleaner fish at the moment". At the time there were 793,000 salmon on sites of average weight 830g.

On 29th September 2015, Loch Duich was inspected and the FHI reported that the "manager had hoped to have stocked wrasse (wild caught) at the start of the cycle, but not as many being caught. Thought to be getting wrasse in a couple of weeks". At the time there were 842,769 salmon on site of average weight 1.65kg.

Fisheries scientists are firm in their conclusions that sea lice produced on fish-farms harm wild salmonids, both at an individual and at a population level. However, these threats are not being addressed by effective regulation and control of sea lice numbers on fish-farms in Scotland, which are essential to protect wild fish populations which are already significantly reduced.

Mr Graham-Stewart continued:

"West coast salmon fish-farms have long been releasing huge numbers of juvenile sea lice into the surrounding sea loch environments with serious implications for local wild salmon and sea trout populations.

All supermarkets have a huge part to play in protecting wild salmon and sea trout by making it crystal clear to the salmon farmers that they will not buy and then sell on to their customers any farmed fish from those Scottish farms that cannot or will not control their sea-lice numbers.

If Sainsbury's wants to demonstrate its real commitment to wild fish conservation, we would like to invite it to support the S&TCS Petition to the Scottish Parliament, which seeks to change the law, firstly to require immediate culls or harvesting of farmed where sea lice numbers have effectively gone out of control and secondly to give inspectors the legal duty to control sea lice on fish farms, expressly to protect wild fish populations from juvenile sea lice infestation from marine cage fish farms."


1) In December 2015, Salmon & Trout Conservation Scotland (S&TCS) published a detailed report into the control of sea lice on fish farms in Scotland over the last two years, brought into sharp focus the seriousness of the problem with sea lice and the need for urgent action from the Scottish Government to protect wild salmon and sea-trout populations that are already in trouble. The Report highlighted many regions of the Scottish Highlands and Islands where fish farms were collectively above, often very significantly above, the industry's own 'good practice' threshold (based on the number of adult female lice per farmed fish). At many of the fish-farms, despite repeated chemical treatments against sea lice, including using synthetic pyrethroid and organophosphate chemicals, the regional on-farm sea-lice levels remained stubbornly high. The Report made a number of recommendations for action from the Scottish Government, which the supermarkets are encouraged to support, including

  • requiring the immediate publication of farm-specific sea lice data
  • tougher regulation and inspection of fish farms;
  • a Government-led review of the current voluntary code of practice, replacing it with a statutory code, as provided for in the Aquaculture Act 2007;
  • introducing an 'upper-tier' sea lice threshold above which an immediate cull or harvest of farmed fish is required by law;
  • amending Scottish legislation to protect wild fish from potential damage caused by fish-farms, with inspectors given a legal duty to control sea lice on fish-farms in order to protect wild fish populations;
  • ordering the closure and / or relocation or persistently poorly-performing fish farms;
  • signalling that the fish farming industry will be required eventually to move to full closed containment, to ensure a complete 'biological separation' of wild and farmed fish.

2) Sea lice numbers in Loch Long and Croe (Loch Alsh, Loch Duich and Ardintoul fish-farms all run by Marine Harvest):

  Sea-lice counts CoGP threshold
October 2015 1.24 1
November 2015 4.48 1
December 2015 6.78 1

3) Just what is the problem with sea lice?

Adult wild salmon are perfectly adapted to coping with a few sea lice. Background levels of these parasites occur naturally in the sea. However the advent of salmon farming, particularly in fjordic 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 rampant breeding reservoir pumping huge numbers of mobile juvenile sea lice out into the local marine environment. The consequences when wild salmon and sea trout smolts, the metamorphosing fragile skin of which is not adapted to cope with more than the odd louse, migrate from local rivers into this "sea lice soup" can be devastating.

Carrying an unnaturally high burden of sea lice is known to compromise severely the survival of juvenile migratory salmonids. 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. Quite literally, the fish are eaten alive. Badly infested 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 through sweep net operations.

4) In 2015, the Scottish Government published its classification of the country's rivers' salmon populations. This places all the rivers in the west Highlands and inner Hebrides in the worst-performing category, with wild salmon stocks not reaching their conservation limits, which are a measure of the overall health of the population. No river within salmon farming's heartland of the west Highlands and inner Hebrides has, according to the Scottish Government's own scientists, a sufficient stock of wild salmon. See more here

Sea trout populations too are under considerable threat with the number of sea trout returning to Scottish rivers in decline, with the 2013 rod catch being the lowest on record according to Marine Scotland Science. The west Highlands has in recent decades lost all of its formerly prolific loch fisheries for sea trout.

The negative impact of sea lice, produced in huge numbers by fish farms, on wild salmonids (salmon and sea trout) is widely accepted by fisheries scientists including the Scottish Government's own Marine Scotland Science.

5) A paper published in 2013 by a group of fisheries experts from Norway, Canada and Scotland re-analyses data from various Irish studies and shows that the impact of sea lice on wild salmon causes a very high loss (34%) of those returning to Irish rivers – see M Krkosek, C W Revie, B Finstad and C D Todd (2013) Comment on Jackson et al. Impact of Lepeophtheirus salmonis infestations on migrating Atlantic salmon, Salmo salar L., smolts at eight locations in Ireland with an analysis of lice-induced marine mortality – Journal of Fish Diseases.

Most importantly, there is clear evidence that both wild salmon and sea trout are in decline in Scotland's 'aquaculture zone', whereas, generally, populations have stabilized on the east and north coasts where there is no fish-farming see here

In 2015, fisheries scientists from Norway, Scotland and Ireland reviewed over 300 scientific publications on the damaging effects of sea lice on sea trout stocks in salmon farming areas, and examined the effect of sea lice on salmon, concluding that sea lice have a potential significant and detrimental effect on marine survival of Atlantic salmon with potentially 12-29% fewer salmon spawning in salmon farming areas. The researchers concluded that: "Salmon lice in intensively farmed areas have negatively impacted wild sea trout populations by reducing growth and increasing marine mortality. Quantification of these impacts remains a challenge, although population-level effects have been quantified in Atlantic salmon by comparing the survival of chemically protected fish with control groups, which are relevant also for sea trout. Mortality attributable to salmon lice can lead to an average of 12?29% fewer salmon spawners. Reduced growth and increased mortality will reduce the benefits of marine migration for sea trout, and may also result in selection against anadromy in areas with high lice levels. Salmon lice-induced effects on sea trout populations may also extend to altered genetic composition and reduced diversity, and possibly to the local loss of sea trout, and establishment of exclusively freshwater resident populations." See Thorstad , E , Todd , C D , Uglem , I , Bjorn , P A , Gargan , P , Vollset , K , Halttunen , E , Kalas , S , Berg , M & Finstad , B 2015 , ' Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta – a literature review ' Aquaculture Environment Interactions , vol 7 , no. 2 , pp. 91-113 . (at