Figures show sea-lice explosion in Loch Fyne and Loch Torridon salmon farms in spring 2015

Scottish Government called upon to copy Norway and start issuing 'cull orders' to tackle out-of-control sea lice issue on Scottish fish farms. Time for robust action on threat to wild salmon and sea trout conservation

The latest Scottish fish-farm industry figures on sea-lice numbers on Scottish salmon farms show that average sea-lice numbers on the ten farms operated by The Scottish Salmon Company in Loch Fyne rose to nearly 23 times the industry thresholds for adult female sea-lice parasites, at the worst possible time for the emigrating wild salmon and sea-trout smolts.

This occurred despite the company using 86 (eighty six) treatments at its sites in the 9 months to March 2015, including 5 co-ordinated treatments (where all farms are treated at once), which must call into question whether the treatments can or should still be relied upon.

Over the same period, the sea-lice figures for Loch Torridon show that average sea-lice numbers aggregated for the one farm operated by Marine Harvest at Torridon and the three farms operated by The Scottish Salmon Company at Kenmore, Aird and Sgeir Dughall also rose to nearly 21 times above the industry thresholds for adult female sea-lice parasites, despite 35 (thirty five) treatments for lice in the 9 months to March 2015, including 5 co-ordinated treatments (where all farms are treated at once).

These shockingly high lice numbers on the fish-farms will have meant that wild salmon and sea trout in and around both Loch Torridon and Loch Fyne will have faced a huge risk of sea-lice infestation, disease and death from the millions of mobile young lice produced from these farms.

The graphs below, drawn up by S&TA(S) using SSPO sea-lice and SEPA biomass data, show the adult female lice numbers on both the Loch Fyne and Loch Torridon farms against the total biomass of farmed fish on those farms.

The graphs shows lice levels rising to well over Code of Good Practice thresholds in 2015 as the biomass of fish in the farms increased.

On Loch Fyne, The Scottish Salmon Company blamed "unusual environmental conditions in the latter months of 2014 with unseasonal warm water temperatures" which "resulted in increased levels of sea lice generally, including also in the Loch Fyne area".

It is surely no coincidence that two juvenile sea trout caught in May in sweep-net monitoring close to Loch Torridon each carried over 500 sea lice – an unprecedented and almost certainly fatal level of infestation.

The lice-infested pectoral fins of a juvenile sea trout caught near Loch Torridon in May 2015. The total burden of sea lice was over 500. Photo – copyright James Merryweather.

Where is the cull?

The S&TA(S) believes that these new numbers mean Scottish Government should have ordered a complete cull of all the farmed salmon in these farms some months ago, to protect wild salmon and sea-trout, along the lines of that ordered by Norwegian authorities in the Vikna district of Nord Trondelag, in order to protect migrating their wild salmon and sea trout in the spring of 2014.

The Scottish Government has the legal powers under section 6 of the Aquaculture Act 2007 to issue 'cull orders' but have never used them to order a cull of heavily-liced farmed fish.

This compares very badly with the actions of the Norwegian Government which served a total of 7 of its fish farm sites with orders for compulsory slaughtering in 2014. The corresponding number for 2013 was 8.

In addition 7 Norwegian fish-farms have been given notice their permitted biomass may be reduced in 2014 to control sea-lice levels.

The S&TA(S) also wants to see the maximum biomass at consistently 'licey' Scottish farms dramatically reduced to a level at which the fish-farmers can demonstrably control sea lice.

Andrew Graham–Stewart of S&TA(S), said:

"Wild salmon and sea-trout are a key part of Scotland's world-renowned natural heritage, but the latest figures for wild salmon numbers are very poor indeed. We know that wild fish need a huge conservation effort.

What we simply cannot afford now is fish-farms like those in Loch Fyne or Loch Torridon pouring millions of mobile young lice into the paths of migrating juvenile salmon and sea-trout.

The question for Scottish Government is 'how much more evidence of failure to control lice do you need before you start to use your powers to protect wild fish?'"

Guy Linley-Adams, Solicitor to the S&TA(S) Aquaculture Campaign, commented:

"Conservation bodies keep being told that salmon-farming is a highly-regulated industry, but regulations only work if they are enforced.

Those parts of this industry that fail to control lice must now face robust enforcement action.

The statutory powers to control on-farm sea lice numbers to protect juvenile wild fish from lethal infestations exist – they must now be used. Its time for the Minister to tell the inspectors to get tough."

Why are sea lice on fish-farms such a threat to wild salmonids?

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 (see Note 1).

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 Note 2).

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 Note 3).


1) Marine Scotland Science (2013) Summary of information relating to impacts of sea lice from fish farms on Scottish sea trout and salmon – 4th April 2013 – see Note also that Marine Scotland Science acknowledges that compliance with the thresholds within the Code of Good Practice is not necessarily sufficient to ensure that juvenile sea lice emanating from the fish farms do not damage wild fish.

See also S&TA (2013) recent research and findings on the impact of salmon aquaculture on wild salmonids – see

2) 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.


S&TA (Scotland):