reLAKSation no 1108

SPILLS (again): In the last issue of reLAKSation I mentioned that in the absence of the delayed SPILLS report, I would provide my own assessment of relevant data that is already in the public domain. According to the webpages dedicated to SPILLS (Salmon Parasite Interactions in Linnhe, Lorn, and Shuna) that appear on the Scottish Government website,

The following data will be used to help validate the existing computerised sea lice dispersal models:

  1. Historic sentinel cage data
  2. Historic plankton tow data as well as new plankton tows
  3. Wild fish monitoring recording sea lice infestation pressure

In this first review of data, I am focussing on the wild fish monitoring programme. However, before I can begin, I need to address a major problem that I have identified with the project. The first of the work packages is described as – The development of sea lice connectivity modelling for the Sound of Shuna. This is then followed by a map which shows an area near Loch Melfort, south of Oban, centred on Shuna, an island, located next to the Isle of Luing. The problem is that the water around Shuna is actually named Shuna Sound. The Sound of Shuna can be found next to Shuna Island, north of Oban. Given the map used to illustrate the project is centred on the southernmost island, I will assume that it is Shuna Sound (red circle) that is the focus of this study and not the Sound of Shuna (blue circle). This may be considered a minor point, but this is a scientific project and as such, everything should be exact.

Marine Scotland Science (MSS) funds annual sea lice sampling from sites across the west coast. Data covering the two years of the project’s run is posted on the Fisheries Management Scotland (FMS) website The SPILLS web page lists only the Argyll Fishery Trust as one of the collaborators, so presumably the sea lice sampling data is from sites administered by this trust. The only such sites listed in the 2021 report are Dunstaffnage just north of Oban and Loch Etive, which is further north still. There is no record of any sampling work around Shuna during that first year. In 2022, the Argyll sites are Loch Etive, Loch Riddon, which is much further south and on a different coastline, and Shuna. The Shuna entry is recorded as sampling by Fyke net rather than the more traditional seine netting. For 2022, Dunstaffnage which has been sampled since 2002, appears to have been dropped as a sampling site, despite the run of nearly twenty years of data.

In 2022, the Fyke nets set near Shuna yielded a total of 133 sea trout. These were caught over fourteen retrievals of the nets meaning that each netting produced a sample of 9.5 fish. The range was from one fish to 24.

Four of the fourteen nettings were in June, nine in July and one in September. Of the 133 fish, 110 carried less than 10 lice, 17 fish had between 11 and 20 with a further 5 infested with between 21 and 30 lice. One fish carried 51 lice.

When the percentage infestation is plotted for all 133 fish, the graph is as follows:

This is an approximation of the classic aggregated distribution, but not as clear cut as would be hoped. The reason for this is not that the data is made up from 133 fish, but rather that the fish were collected in such small samples. More than half the nettings consisted of less than 10 fish and as such are not representative of the parasite population on sea trout. They are more likely to be the fish that are most easily caught, rather than strong healthy fish.

Not one of the nettings met the recommended minimum number of 30 fish established by the Scottish Fish Coordination Centre for seine netting and although Fyke netting is different to seine netting, the sample size should still be sufficiently large to be representative of the sea lice infestation of the sea trout population.

Whilst the SFCC and MSS have established the 30 fish protocol, there appears to be no scientific justification for this number. By comparison, there are several published papers that consider the size of the sample in terms of measurement of parasite numbers. All highlight the problems of small sample sizes. This issue is one which I consider in a paper that I will soon submit for peer-review with the aim to publish in a scientific journal, so I prefer to not discuss this issue here. However, I will mention that Taranger, whose paper the wild fish sector use to assess the risk, suggests that each sample size should be around 100 fish. The number of fish caught around Shuna is far short of this amount.

The lack of fish should not be a surprise. Shuna is in an area that is not well-known for its salmon and sea trout fishing, presumably because there are no significant numbers of salmon or sea trout rivers in the vicinity.  There are four rivers that empty into the seas around Shuna, although not in the immediate area.

The first is the Nell also known as Feochan, because it empties into the sea loch of the same name. In his book of the Rivers and Lochs of Scotland, Bruce Sandison makes no mention of salmon farming when writing about this river, although he is very vocal about the presence of salmon farming elsewhere. Mills & Graesser, in their book of salmon rivers, say that there has been a marked decline in the numbers of sea trout in recent years in the Nell, although they don’t say why. Their book was published in 1981 and at that time, there was one very small farm in Loch Melfort that was associated with trout. Today this farm has a consent for just 250 tonnes.

The first salmon farm in the area didn’t start up to 1987, by which time local sea trout stocks were already in trouble.

The second river is the Oude which empties into Loch Melfort adjacent to Shuna. This is another river that gets hardly a mention by Bruce Sandison, but Mills & Graesser highlight that the river has been developed for hydroelectricity and there are no opportunities for fishing.

The third river is the Barbreck, which empties into Loch Criagnish. There is no information available for this river as even Bruce Sandison fails to mention it, presumably it is not fished at all.

The fourth and last river is the River Add. Bruce Sandison say sea trout are notable by their absence. This was in 2014 but as the graph shows sea trout had long gone from the river. The nearest farm was registered in 1992 but Mr Sandison was already blaming the disappearance of sea trout partly on salmon farming in the first edition of his book which was published in 1997.

In fact, Mr Sandison says that the Add has suffered a variety of unfortunate circumstances over the years from water abstraction for hydroelectricity and massive afforestation of the river catchment.   Mills & Graesser say that the hydro scheme was completed in 1961 and the graph would suggest that it was the hydro that has had a massive impact on fish in the river not salmon farming. They also say that the tree planting has affected movement of gravel and silt in the river.

So, what can be concluded from the 2022 netting around Shuna? Using the Wells threshold (which I believe to be a highly over-estimate of risk) just 11% of sea trout are at risk from sea lice. That means 89% of sea trout are not at risk. Once the SPILLS report is published then I will be able to see whether the same conclusion is reached.

After analysing the 2022 data, I happen to conduct a Google search for some unrelated information and totally by chance I came across a report from the Argyll Fisheries Trust (AFT) titled ‘Sea Lice Burdens of Sea Trout at Sound of Shuna, Argyll 2021’.

This report totals 24 pages in length (including the cover page) and my first reaction was that I was extremely impressed that AFT had found so much to write about because in total, they had caught just 13 fish around Shuna throughout the whole year. Yet despite writing such a comprehensive account, I found much that had been omitted, not least the actual number of lice counted on each of the thirteen fish.  The AFT have now kindly supplied the missing data so a big thank you to them. The lice infestation ranged from 0 to 55 lice.

The way the report is written makes it difficult to associate which fish were caught when and by how – they used both seine netting and Fyke nets in 2021 but it seems that whilst seine netting took place at six locations in two lochs, the four fish caught by seine net came from just one location in Loch Melfort on one date.

The remaining nine fish were caught by Fyke net. These nets were placed in three locations for between 25 and 43 days with the nets being checked regularly.

The main findings of the report include that the low number of samples analysed in 2021 make firm conclusion difficult to be drawn but the limited data suggest that here was a lice-related risk to sea trout in the Sound of Shuna. I would disagree. The low number of samples simply means any conclusion is impossible to draw. This is even more so, when the number of fish caught by each netting was so low. The most fish caught in one netting was three. Any results are therefore totally meaningless, and it is likely that AFT’s conclusion has been reached only because of a preconceived view that the presence of any sea lice on wild fish must be associated with a salmon farm and therefore such sea trout must be at risk.

One other finding listed is the suggestion that when compared with historic data collected in Loch Craignish, the 2021 results show a similarly high sea lice related risk of mortality that was found in 2008 for smaller trout. In the main body of the report, it is claimed that the sea lice burden (of 13 fish) in 2021 was higher than in fish sampled in 2008, 2009 and 2010.

In 2010, only one fish was sampled for the whole year, whilst in 2009, it was just two fish. The 2008 sample consisted of 33 fish, 25% of which were lice free and 70% were below the Wells threshold. The distribution of lice followed an aggregated distribution, although not a classic one, due to the small sample size. This data certainly does not support any of the claims made by AFT.

I would suggest that the small and very small samples sizes from 2008 to 2010 brought into question whether any meaningful data could be achieved from sampling Loch Craignish, which I presume is why AFT chose to stop sampling after 2010 preferring to direct their efforts elsewhere instead. If Loch Craignish was such a poor site for sampling sea trout for sea lice in 2008 to 2010, why was Shuna selected as the primary location to validate the sea lice dispersal model?

My final question is that although only 13 fish were sampled in 2021, why do not these fish appear in the official FMS dataset? After all, the one fish sampled in Loch Craignish in 2010 does, as do the two fish sampled in 2009.


Appy: The Scotsman newspaper reports that anglers have been asked to help tackle the invasion of alien fish that threaten the survival of native Scottish salmon. Fisheries Management Scotland have developed an app whereby anglers can report any pink salmon they catch. FMS also have apps to report the presence of disease and any escaped farmed salmon.

Rather surprisingly FMS do not have an app for reporting any salmon or sea trout that anglers have caught during their day-to-day fishing activity. I fail to understand why the wild fish sector has no way of reporting the catch from rivers across all of Scotland which can then be processed and published daily. Currently, the official catch data is not published until April or May the following year which means that it could be eighteen months before catch data is reported. Following the SIWG report, Marine Scotland Science were supposed to be investigating ways to make more up to date catch available in the public domain. They did appoint a company to look at this but no word since. MSS have probably been far too busy sorting out sea lice dispersal models to focus on bringing angling reporting into the current century.

Surely, a national in-time reporting system shouldn’t be beyond the realms of possibility especially as the wild fish sector claim that wild fish stocks are in crisis.


Sprung into spring: The MSS salmon statistics report for 2021 (we are still waiting for the 2022 data to be published) includes the following graph.

The green line shows the status of the spring component of the salmon catch. The spring catch is clearly in a perilous state. In the past, the Scottish Government has imposed mandatory catch and release on fishing for this early stock however, given that there is no improvement the question is why the Scottish Government allows anglers to continue fishing for these threatened salmon.

This week, the River Tay new season opening was marked with all the pomp and ceremony they could muster. This included blessing the river with whisky, a pipe band and actor Burn Gorman and travel author David Profumo making the first cast.

The Daily Record reported that there have been concerns that the numbers of salmon in the river have not been what they used to be, however the Tay District Salmon Fishery Board said that they were looking forward to the implementation plan for the Scottish Government’s Wild Salmon Strategy.

It is over a year since the Scottish Government published the strategy and the Tay Board say that this unique initiative recognises that wild salmon are in crisis and seeks to prioritise work for their restoration. The plan is now imminent and the Tay Board hope that it will give appropriate urgency to tackling the issues that the Board cannot undertake directly as they require actions from other bodies and agencies. They cite the long-standing water abstraction issue on the River Ericht at Blairgowrie as requiring attention. However, resolving local water abstraction issues is not going to address the issue of declining salmon stocks and nor is any other part of the Wild Salmon Strategy. It fails to consider the underlying issues which the wild sector has ignored for many years.

Meanwhile, the Tay Salmon Fishery Board do have the ability to take direct action whilst making a clear statement of their intent. Rather than open the fishing in January, they should postpone the ceremony until after the spring run has finished. It is recognised that the Spring Fish are under threat so why do they continue to hunt and stress them?


Pink invasion: As I was about to post this latest issue of reLAKSation, I came across a reference to a new paper in the Journal of Fish Biology.  This provides evidence that Pink salmon have bred in Scottish rivers, namely the Thurso and the Oykel. In total 95 Pink salmon smolts were caught from the Thurso and a further 25 were netted in the Oykel during March 2022.

It is now January 2023. Why is this the first mention of this major discovery and why is it reported as a scientific paper? It seems that there might have been more interest in publishing a paper than sharing the discovery.

The paper has seven authors including Alan Wells of Fisheries Management Scotland, and organisation that also posts news stories on its website. This week, they posted a story from the Northern Times about how the River Thurso is in tip top condition as it opened for the 2023 season. The river’s scientific consultant is another of the paper’s authors. He told the Northern Times that the river is producing everything it needs to sustain a healthy population. The problems are out at sea – lack of feeds, predation, drift nets at sea – all things completely out of our control. Yet, no mention of Pink salmon smolts in the river.

Why is it that the salmon farming sector has to report a variety of parameters on a regular basis yet, the wild salmon sector still appear to supress up to the minute data. The Northern Times article reports that anglers on the Thurso caught 788 salmon last year. If I hadn’t read this detail in the newspaper, I would have to wait for MSS to publish the official catch data in three months’ time.

The current state of wild fish stocks in Scotland is regularly blamed on salmon farming by the wild fish sector but the reality is that they need to take a really good look at themselves. Their failure to report these Pink salmon smolts outside their little clique is clear indication of all that is wrong with the wild fish sector.