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reLAKSation no 1100

MASTS: Last week, Marine Alliance for Science & Technology in Scotland (MASTS) held their annual science meeting in Glasgow. Unfortunately, I was unable to attend although. I would have like to have been there as amongst those giving a presentation on Tuesday afternoon was Dr Meadhbh Moriaty from Marine Scotland Science (MSS). The title of her presentation was “Salmon Parasite Interactions in Linnhe, Lorn and Shuna – Sea lice dispersal model evaluation using an ensemble approach”. Dr Moriaty had 12 minutes to speak unlike the 5 minutes she was given at Sea Lice 2022 back in May. It would have been interesting to hear what new information she supplied in the extra 7 minutes. MASTS have published a sort of abstract and the impression I have obtained is that the marked differences between the three models – SAMS, MSS and Industry that she reported in May might now be less marked. I am guessing that it wouldn’t do for the modelling at the heart of the SEPA risk framework to be shown to be questionable.

It does seem that Dr Moriaty is keen to inform the wider scientific community about her sea lice modelling work. I know that there are many in the salmon farming industry, towards which her work is actually targeted, who would welcome the same opportunity to hear about the model, sea lice dispersal and how her work relates specifically to salmon farming.

Sea Lice 2024 is coming to Scotland, but I believe that there is already talk of a smaller one-day meeting to be held in the spring of next year that will consider the science as it applies to the industry, whether published or not. I would expect that Marine Scotland Science will be active participants of this meeting, not just Dr Moriarty. This is because she was not the only one of the MSS family to present at Glasgow. Another presentation considered small-scale movements of sea lice dispersion in Loch Linnhe. I am not quite sure of the aim of this work, but I was struck by the final paragraph of the abstract. This says:

“While sea lice modelling has improved during the last 15 years, this study suggests that the use of numerical models for effective management of sea lice would benefit from more observational data to reduce uncertainties.”

Could it be that there is now some recognition that particle dispersal models just show dispersal of inert materials, which could be something as simple as a plastic duck, whereas biological material such as larval sea lice may behave in a completely different way. This would explain why Karin Boxaspen, as discussed in reLAKSation no 1098, was unable to find larval sea lice in the water column in any significant number!  They don’t act as inert particles.

We must continue to wait to find out what the SPILLS project has discovered. However, a report will not be enough, and I will certainly look forward to hearing a full account at a sea-lice meeting in spring next year.


VRL: The Norwegian Scientific Advisory Committee for Atlantic Salmon (VRL) has published the short summary in English of their latest report on the status of wild salmon in Norway in 2022. In this they summarise the various impacts on wild salmon encountered in Norwegian waters. This includes the impacts of sea lice, which they say has the greatest negative impact on wild fish. Not only, are sea lice the greatest threat, but the Committee say that they have the highest confidence in saying that sea lice are the greatest threat.

Sadly, the short description does not inspire such confidence in their certainty (or their knowledge). This begins:

“The number of salmon returning to the rivers each year is reduced due to mortality caused by salmon lice. This reduction threatens salmon populations in the most impacted areas, and has significantly reduced the harvestable surplus for angling and marine fisheries over large parts of the country. In 2010-2014, we estimated that 50 000 fewer salmon returned from the ocean to Norwegian rivers each year due to the impacts of salmon lice. For 2018, we estimated a reduction of 29 000 salmon due to salmon lice, and for 2019 a reduction of 39 000 salmon.”

Interestingly, the 2020 report begins:

The number of salmon returning to the rivers each year is reduced due to the impacts of salmon lice. This reduction threatens salmon populations in the most impacted areas and has significantly reduced the harvestable surplus for angling and commercial fisheries over large parts of the country. In 2010-2014, we estimated that 50 000 fewer salmon returned from the ocean to Norwegian rivers each year due to the impacts of salmon lice. For 2018, we estimated a reduction of 29 000 salmon due to salmon lice, and for 2019 a reduction of 39 000 salmon.

Not surprisingly, the 2021 report says the same thing. It would appear that VRL have made absolutely no effort to uncover whether the impacts have changed preferring to repeat the same old narrative.

The 2019 report was different. This did not even have a section about sea lice but included the following in a minor section about salmon farming.

The number of salmon returning to the rivers each year is reduced due to the impacts of salmon lice, and this reduction of salmon populations has reduced the harvestable surplus for angling and commercial fisheries. In 2010-2014, we estimated that 50 000 fewer salmon returned from the ocean to Norwegian rivers each year due to the impacts of salmon lice. For 2018, we estimated a reduction of 11 000 salmon due to salmon lice.

Unfortunately, VRL do not relate the number of salmon killed by commercial or recreational fishermen except to say that in 2018, this was about 500-600 tonnes in recent years. Taking an average of those figures and an average estimated weight of 4kg for a salmon, then typically, 137,000 fish would be lost to Norwegian rivers by such exploitation. Why an estimated loss of 11,000 salmon to lice (a figure which I think is highly overstated) is considered the greatest threat to wild salmon when 12 times as many are killed by exploitation remains a complete mystery.

What is interesting is to compare the graphs produced by VRL showing the most important factors affecting wild salmon in Norway.  In 2018, the graph was:

The two points of interest are the green square bottom left. This is the risk to wild salmon form overexploitation. The green square means that there is much knowledge of this issue. Over-exploitation is considered low risk, but this refers to exploitation above the current level which VRL consider acceptable. The second point is the yellow circle towards the top right. The top circle is escaped farmed salmon, the lower yellow circle is sea lice. The yellow circle indicates moderate knowledge.

Yet, one year later, the graph has changed. Overexploitation remains the same, but sea lice has risen to the greatest threat and the knowledge has improved from moderate to extensive as shown by the green square.

I am not sure what VRL learnt in 2019/2020 about sea lice to improve their knowledge so significantly because it is not reflected in their report, which provides no new information.  VRL are unable to even hazard a guess to the estimated mortality of wild salmon due to sea lice, preferring to reply on a three-year-old statement. Finally, I do note that their statement on exploitation also remains unchanged with 500-600 tonnes of wild salmon caught in recent years.

This is not science but more of a witch-hunt.


Spey declines: There were a lot of interest in the radio programme I highlighted last week. However, some people seemed unable to access the broadcast so I would just mention a couple of points raised. However, before I do, I would like to draw your attention to the Spey online blog which has also written about the programme giving a perspective from the wild fish sector. It is very much worth a read. There is also a different link to the radio programme for anyone who still hasn’t heard it.

The following photo comes from the blog.

The programme focussed on the sorry state of decline in salmon stocks in Scottish rivers over the previous ten years or so and it seems that this rate of decline is accelerating. The River Spey Fishery Board believed that part of the problem was a dramatic swing from spring to summer stocks with many less fish appearing in the river earlier in the year. They say that there might be the same number of fish in the river as before but now there are fewer available for exploitation.

A local ghillie said that he had been on the river for 36 years but that the last ten years were the worst he had seen. He related how in the past, they used to kill 500 salmon on their beat during April and May. Now they are only killing double figures in a week, whereas they used to kill that in a day.

The programme narrator said that there appears to be a lack of sound basic information. In my opinion, it seems that not much has changed. After all, given the outcry about the state of wild fish stocks as illustrated by FMS’s call to action, there has been very little published about the actual state of wild fish stocks in Scotland. FMS publish their annual review, but this is more about the state of angling in selected rivers than the needed wider view. Even the wild salmon strategy glosses over the issue relying on just one graph to make its point. It was therefore interesting to see that the Scottish Government’s 2023 river grading assessment included a document titled ‘International and National stock trends.’ Sadly, this document, like many published by Marine Scotland Science is hidden away rather than being widely shared.

However, the document offers nothing new in terms of information that those working in the area are already well versed. This is that the numbers of salmon returning to Scottish rivers has been in decline since the early 1970s (if not before). This pattern is repeated across all of Scotland.

The last time I saw similar documents was from stock assessments dated 2013 and 2014. I refer to these because of their relevance to the BBC broadcast highlighted above. This is because both documents discuss not only the perilous state of spring salmon, but also look at the summer and autumn components too. When I began looking into the state of wild salmon, there seemed to be a lot of talk of spring, summer and autumn catches but very little since, although MSS do publish one graph with the annual salmon fishery statistics. The fact that summer and autumn catches mirror the total catch indicates that spring salmon catches have always been a relatively low part of the catch.

In 2014 and 2015, MSS published a status report of wild fish stocks for 2013 and 2014. These include an assessment of the seasonal stock components but here I will only consider the spring catch. The section headed spatial and temporal variability in rod and line catches begins in both documents:

“At the national scale, reported catches of spring salmon have declined over much of the time since records began in 1952. Catches have stabilised in the past two decades, albeit at a lower level (fig 2.).  Examination of the last 20 years of catches at a district scale reveals a varied picture- ..”

The two documents then separate into two different narratives.

The 2013 stock assessment (2014 report) states:

“…reveals a varied picture without a clear regional coherence. Of those 30 districts where returns were adequate to allow allowed (sic) the rod catch tool to be applied there is no evidence of a trend in the majority (20) of districts, declines in 1 and increases in 9.

This is illustrated with figure 2.“

In case the text is too small to read, blue areas show an increase, grey no trend and orange shows a decline.

By comparison, the report published just one year later for the stock assessment in 2014 continues from the point where the two reports diverge:

…reveals a varied picture, although there appears to be a cluster of rivers centred around the Spey which exhibit significant declines. Of those 37 districts, where there were sufficient data to enable application of the rod catch tool, there is no evidence of a trend in the majority (22) of districts, declines in 13 and increases in two.

How can these two graphs separated by one year but covering the same twenty years of data bar one, be so different in their analysis. This question does not seem to have been answered nor has what happened in subsequent years. How can the Spey cluster be seen to exhibit significant decline in 2014 yet one year earlier show no evidence of any trend? This is not something that anyone else has seemed to question? Does no one in the wild sector care?

My perspective on this is that MSS eventually started to undertake a deeper analysis of fish catches in 2014 but when they were finally forced to implement conservation gradings on Scottish rivers, some twenty years after the same had been introduced to English and Welsh rivers, they focussed their efforts on the gradings rather than try to understand the changes to Scottish fish stocks, so these annual analyses of trends were abandoned.

Of course, MMS were also busy with other projects. At the same time, these reports were abandoned, MSS were embarking on an extremely ill-conceived and unnecessary three-year project to demonstrate that sea lice from salmon farms do have an impact on wild fish. As their current Summary of Science shows, MSS have had great difficulty accepting that sea lice are not the problem that some people claim. MSS have very much downplayed the work of the Irish Marine Institute who showed on a large-scale experiment that mortality due to sea lice was around 1% of migrating salmon stocks. Instead, MSS progressed their own £600,000 study to prove that the Irish study did not apply to Scottish rivers. As expected, the study was a disaster because of 3,231 fish, just 2 were recaptured, one control and one experimental.

The study was flawed because it aimed to use wild caught smolts and as everyone knows, there aren’t that many in the west coast. Whilst the MSS study used 3,000 fish over two years, the Irish study employed 352,000 fish over nine years. Despite the (predictable) failure of the MSS study, they have continued to focus their efforts on the impacts of salmon farming rather than investigate what is causing the declines in wild fish across all of Scotland.

Finally, I return to the document on international and national stock trends. In the section about river gradings for 2023, MSS state:

“The grades which form the basis of the annual Conservation Regulations are based on the latest 5 years of data. While the assessments incorporate information on declining abundance, they do not predict what will happen in the future.”

After all these years of research, I would have thought that these expert fisheries scientists might be willing to hazard a guess at what will happen to wild stocks in the future. The wild fish sector appears to believe that if salmon farming is removed from the west coast, then stocks will revert to former levels across all of Scotland allowing them to continue their sport without a further thought.  However, I take a different view. The trend graphs stretching back fifty years that appear in the MSS stock trend document show all that anyone needs to know. Anyone who cannot see the inevitable is simply burying their head in the sand or would rather blame salmon farming.