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reLAKSation no 1098

SPILLS: In 1997, Karin Boxaspen, now research director of the Norwegian Institute of Marine Research, published a short paper in the ICES Journal of Marine Science. The abstract begins:

“Surveys in the area around Austevoll Aquaculture Research station have failed to reveal the presence of a large number of the free-swimming stages of salmon lice in the water column. However, lice were abundant on salmon held in cages in the area”.

The introduction to her paper begins that:

The first three stages of salmon lice, which are free-swimming, are very difficult to find in nature (Tully & Whelan 1993, Costelloe et al 1996).

These are not the only papers from around this time, which report similar observations.

Even though several studies have not found significant numbers of lice in the water column, research has continued to focus on the idea that salmon farms eject millions of infectious larval sea lice that are either wind-blown or carried large distances on the currents in the expectation of encountering a host wild fish. The mainstay of this research has been the development of hydrodynamic and particle modelling that can predict the dispersal of lice away from salmon farms. The proposed SEPA risk framework is based on such models.

Unfortunately, the major flaw with these models is the apparent blind acceptance that they actually reflect what is happening in the real world.

I was recently asked by someone who reads reLAKSation, if I had any thoughts on the SPILLS project. At the time, I didn’t have any thoughts on SPILLS because I had never heard of it and had no idea what it was. This was not surprising because whilst Marine Scotland Science have posted details of the project on the Scottish Government website, they haven’t publicised anything about it, so it remains in plain sight but yet totally invisible.

SPILLS stands for ‘Salmon Parasite Interactions In Linnhe, Lorn, and Shuna’. The two-year project ran from October 2020 and I am led to believe that the final report could be due at any time. The project is summarised as:

“Computer modelling is increasingly being used to assess the potential risks posed by sea lice originating from salmon farms in Scotland to wild and farmed salmonids. A number of models are currently used by different organisations, but further rigorous calibration against field data is required.”

The project covers two study areas, Linnhe & Lorn and Shuna and the scientific study comprised of 4 different elements. Two of these relate to the modelling whilst the other two will include a monitoring strategy for infective planktonic sea lice stage and a wild fish monitoring strategy. From my point of view, it is the two latter elements that are the most interesting especially as the outcomes will surely determine the future of the SEPA risk framework.

Full details of the project from the Scottish Government website can be found at:

The first project element of interest is monitoring of larval lice. Given that researchers in the late 1990s could not find the soup of larval lice that is supposed to emanate from salmon farms, I would be surprised if they found anything different. We already know from a paper by Nelson in 2016, that lice on farms tend to stay within the farm and that even within a very short distance, the concentration of lice in the water column is very low. This paper was presented at Sea Lice 2016 in Ireland so is not unknown to the scientific community.

Clearly, if the SPILLS project is unable to find significant levels of larval sea lice in the water column, then the future of the SEPA risk framework must be questioned.

The second project element focusses on the area covered by the Sound of Shuna Environmental Management Plan where a coordinated sampling of wild salmonids was undertaken. This will include infestation pressure on wild fish.

To the best of my knowledge, the attached map shows the area around the Sound of Shuna included in this study:

The farms within this area are identified together with their date of registration.

The decision to select this area to conduct the monitoring programme is rather surprising since it is not an area rich in salmon rivers. In fact, the area is somewhat devoid of any notable salmon fishing. It is unclear where the SPILLS teams sampled wild fish for sea lice since there are no established sampling sites within the immediate area around the Sound of Shuna.

The Argyll Fisheries Trust who are participants in the SPILLS project have been sampling for sea lice on wild fish since at least 1997. There are three general locations in the wider vicinity of the Sound of Shuna. Each location has been sampled at two adjacent sites. These are Dunstaffnage which is about 30 km north as the crow flies, Feochan, at about 15 km north and Craignish, which is separated from Shuna by a headland to the east.

Marine Scotland Science have published a spreadsheet of all the sea lice sampling conducted in Scotland between 1997 and 2019. The analysis below relates to this data. No sea lice sampling was conducted during 2020 due to Covid. Sampling restarted in 2021 and the results are posted on the FMS website. Of the sites highlighted, only Dunstaffnage was sampled. This occurred three times 24th May, 7th June and 22nd June. The number of fish sampled were 7, 10, and 10 respectively all of which fall well below the 30 fish threshold determined in the SFCC netting protocol and thus should be disregarded.

In total, 1,069 fish were sampled at Dunstaffnage between 2002 and 2008 and then 2010 to 2019. This number of fish caught in 42 nettings.

The adjacent site at Connell sampled in 2007 and 2009 a total of 5 times.


The sample nettings highlighted in yellow are those that meet the 30 fish threshold. This amounts to just 13 nettings out of the 47.

When the lice counts are plotted by increased level of infestation expressed as a percentage, the graph is as follows. This is the typical aggregated distribution that is expected with the majority of fish lice free or with minimal numbers of lice.

I am sure that the keyboard warriors will criticise this analysis by suggesting that by selecting only some of the data, I have manipulated it to suit my own narrative so here is the graph of all the nettings whether they meet the protocol or not.

The second location is Feochan which was netted 13 times between 2004 and 2009. The adjacent Loch Feochan was sampled three times in 2010. Two hundred fish were caught in total.

Only one out of the sixteen nettings was within SFCC netting protocol of 30 fish.

The final location was in Loch Craignish with two sites sampled a total of three times during which 36 fish were caught.

Only one out  of the three was within SFCC netting protocol of 30 fish.

Of the three locations surrounding the Loch Shuna area, only 22% of the netting conducted were within the SFCC 30 fish protocol thus 78% were invalid.

It is clear that the sea lice counts on these fish show that the majority of fish are lice free and that any observed infestations are not impacting wild fish populations. Much of the criticism of salmon farming is actually fuelled by pictures of selected fish with high lice counts and claims that these are representative of the whole population, when they are not. It is unclear why research on wild fish populations is not being directed at the real issues, instead of continuing to focus on sea lice.


In addition to sea lice infestations, SPILLS aimed to monitor the abundance of wild fish populations. As mentioned, this is an area that is relatively devoid of salmon rivers and thus any associated wild fish. Although there are accounts of local rivers going back to the early 1900s. there are two more recent guides to salmon rivers in Scotland. Thee first is ‘The Salmon Rivers of Scotland’ by Derek Mills & Neil Graesser published in 1981, so before salmon farming really became established. A more recent description come from the 1997 and 2013 editions of the ‘Rivers and Lochs of Scotland – The Angler’s Complete Guide’ by angling journalist and anti-salmon farm campaigner Bruce Sandison.

The rivers that merit a description include:


River Oude

The river Oude emerges into the head of Loch Melfort.

The Oude is only accessible to fishing for 800 yards according to Mills & Graesser. This is because the Hydro-Electric Board have developed the river for power generation. However, there is no angling available on the river.

Bruce Sandison only refers to fishing for brown trout in the Oude reservoir, as the river Oude and the associated Loch Na Druimnean are private waters unavailable for fishing.

The River Oude lies in the Awe fishery district. This covers a large area and some key rivers. The catches in the district are not reflective of this locality due to the absence of fishing.


The catches of both salmon and sea trout in the wider fishery district show a decline that began long before the arrival of salmon farming to the area.


River Barbreck

The river Barbreck runs into the head of Loch Craignish. The only mention of this river appears in the 1997 edition of Bruce Sandison’s book, but it is not included in the later edition. Mr Sandison refers to the river as a private water reserved for the sole use of the proprietor.

The river is located in the Add fishery district and any fish caught is recorded with those from the other main river in this fishery district – the River Add.


River Add

The river empties into the sea into Loch Crinan, south of Loch Craignish.

According to Mills & Graesser, the Hydro-Electric Board tapped the upper waters of the river Add and diverted the waters to Loch Glashan, where it is used to power the Loch Gair power station. The river now exists with a compensation flow regime and relies on heavy rain to produce large spates. The extensive afforestation of the area also affects the flow of the Add.

The river has a late run of salmon and the main grilse run is in June and Mills & Graesser provide details of salmon catches from 1954 to 1962 but these also appear in the MSS catch data shown later. They say that catches were much better 100 years earlier with records showing that 992 grilse and 53 salmon were caught in 1858 and 1154  grilse and 55 salmon just four years later. Around that time the average catch was 28 salmon and 385 grilse.

Bruce Sandison writes that the high catches of the 1800s fell to 180 fish by the 1950s and in his 1997 edition, he reports that returns were then about 30 fish. By 2013, he was also blaming salmon farming for the declines with 10 fish caught on a good year. However he also states that in 2008, more than 35 salmon were caught which suggested to him that the river was showing signs of improvement.

The catch data for the Add fishery district shows that declines of wild fish began long before the arrival of salmon farming to the coast.


The most recent catches from the river Add, as distinct from the fishery district, are recorded by Marine Scotland Science and are shown as follows:

It is also clear that if such west coast salmon rivers are increasingly devoid of fish, then the cause is not salmon farming. The rivers considered here were depleted long before salmon farming came to the west coast, but it is and has been so much easier to blame salmon farming, which is why projects such as SPILLS continue to dominate Government research about the status of wild fish stocks.


Finally, the SPILLS work programme states that MSS have carried out extensive field sampling in loch Linnhe over several years including sentinel cage deployments and plankton tows. The field data will be used to compare and validate three particle tracking models for the period 2011-2013 (why from over ten years ago?) It will be interesting to see how this field data supports the model because I would be extremely surprised, given that Karin Boxaspen and others have yet to find high levels of lice in the water column, if the plankton tows produced any different findings.  In terms of the sentinel cage data, the results have been posted on the Scottish Government website, again you would need to know that the information has been posted as it is not something that has been publicised. The following graph shows the levels of lice infestation from the sentinel cages deployed in the Linnhe system. Although a cage is listed as being deployed around Shuna, there are no results for this cage.

There is no doubt from this graph that infestation pressure on fish in these sentinel cages exposed to dispersed larval sea lice is extremely low.

Although modelling is not my speciality, I mention this because I recently came across a presentation by Dr Moriarty of MSS which she gave at Sea Lice 2022 in the Faroe Islands this summer- . The work she describes is part of the SPILLS project.

The study looks at three different particle tracking models, one academic, one government and one industry, which are then coupled with the Loch Linnhe hydrodynamic model to see how much uncertainty arises from the three different approaches. Each model uses the same source data, and each considers a suite of different biological factors relating to sea lice and then this is checked against the field data.

What they found is that the industry model gave much better fit than the academic and government models: r=.66 as compared to r= 22 and 25. It should be remembered that it is a government model that forms the basis of the SEPA risk framework and thus may need a major rethink.

There are four conclusions at the end of the presentation but only one is key. This is that there must be more observational data in Scotland to evaluate these models.

From this conclusion I can only deduce one key assumption and that is the SPILLS project failed to produce sufficient robust observations to support the model. However, there is another way of looking at this issue and that is the model that is wrong, and the observational data so far collected actually supports a different narrative. I am reminded that Karin Boxaspen, who was a session chairperson at Sea Lice 2022, failed to find large quantities of larval sea lice in the sea. Could it be that the assumed method of dispersal is not how sea lice find their hosts.

Once the SPILLS report is published, the viability of the SEPA risk framework can then be fully assessed with this most up to date information.