Scroll Top

reLAKSation no 1107

Landmark data: I was searching through my files this week and although it wasn’t what I was looking for, I came across the 2011 document produced by the then Rivers and Fisheries Trusts of Scotland (RAFTS) now part of Fisheries Management Scotland. This aimed to refute the claims made by the then Scottish Salmon Producers Organisation that the rate of decline of wild salmon numbers was similar for both east and west coast.

This is a screenshot of the first page of their document – Comparison of the decline of Scottish East and West Coast Salmon Fisheries, which includes a graph of the decline of all catches (net and rod) for both east and west coast. RAFTS state that if catches by all methods are used, the trend remains consistent with that demonstrated by the SSPO. The graph is one that they have constructed using the rate of decline from the level of catch in 1970. Their report continues that this method of comparison is misleading due to inclusion of catches from the  nets. This they say makes comparison complicated. They go on to give a convoluted explanation of why a comparison of rod catches gives a true comparison.

Yet, it is impossible to ignore the fact that the above graph, which was drawn by RAFTS does show that declines on the west coast match those on the east, irrespective of the method of exploitation. If salmon farms were responsible for declines on the west coast, then they would impact nets as much as they would rod catch. Undoubtedly, the evidence from this graph is that whatever is causing the decline, it is the same on both coasts. Despite all the protestations from the wild fish sector, the evidence from their graph is clear. Interestingly, at the time, the BBC reported the release of the RAFTS document. It makes interesting reading:

Its now over ten years on and I would be interested to hear again from the wild fish sector as to why they insist that aquaculture is having an impact on west coast catches, when their own graph says not. I will write to all wild fish organisations and trusts to ask them that question. I suspect that none will reply but I will report back on any responses.

At the same time, I will ask how the following graph of sea trout catches from the west coast shows salmon farming is having an impact on that species. It is clearly apparent sea trout catches were in decline for the thirty years prior to the time when salmon farming started to produce a recordable tonnage. I have asked several times previously whether the declines after the 1980s could be due to the same causes as prior to the 1980s. No-one from the wild fish sector has ever provided an answer. Perhaps, now is the time that the question should be addressed.


Citing science: I often wonder how many researchers cite other published work without reading the published paper simply because it has been cited elsewhere. I often find that citations refer to a single sentence of a paper and the rest of the work is irrelevant to my own research. Yet sometimes, published papers provide a real insight into the subject and unfortunately, such insights become buried in long forgotten works.

I came across a real gem in a review paper, that is often quoted but not in relation to the following. The paper is by Pike and Wadsworth from 1999 and was published in Advances of Parasitology.  In the discussion section about wild farmed salmon interactions, the paper states:

“Long-term fluctuations in wild salmonid populations, based on the interpretation of catch statistics, have been known for many years. In the UK, fisheries statistics have been collected since 1952, and show short-term fluctuations of increase and decrease, but overall showing a declining trend. With the emergence of salmonid cage culture in the late 1960s, followed by dramatic expansion, concern was expressed about its biological impact on wild stocks. In 1989, the recovery of ascending sea trout in Irish rivers, which were frequently, and often heavily infected, mainly with sea lice chalimi kindled a debate which became heated, passionate, and acrimonious, and which involved anglers, fish farmers, government scientists and politicians at all levels, The arguments have continued until the present and have generated as much heat as they have light. The absence of baseline epidemiological data and information on the pathogenicity of sea lice for sea trout has hindered proper scientific evaluation of the perceived problem. Some progress has been made to gather such data, but progress has been slow and establishing cause and effect notoriously difficult. Anglers and riparian owners are understandably exercised by the inability of the scientific community to provide answers because in some cases sea trout populations are alarmingly depleted. However, as Northcott and Walker (1995) point out there are many other possible explanations for the decline including coniferous afforestation, reduced food availability, increased predation, overfishing and unusual climatic conditions. Drawing the wrong conclusions from inadequate data will serve no useful purpose and in the long-term, would hinder progress. “

For me the last sentence sums up much of the research about sea lice over the past decade. Inadequate data has certainly led to incorrect conclusions, and this has hindered progress on sea lice research. A case in point is the focus on models rather than on facts.


Conjecture:  Wild Fish Conservation continue to provide a link to their video about the demise of Loch Maree sea trout. In an extended version, TV personality Jeremy Paxman states that the rise of salmon farming has led to a ‘huge increase in the number of sea lice parasites which sit upon the salmon. What happens then is that the wild fish migrating from the rivers to the sea have to swim through enormous clouds of these parasite and get literally eaten to death’.

Whilst Wild Fish Conservation are happy to spread the message that enormous clouds of sea lice kill wild salmon and sea trout; they are unable to provide any evidence that such enormous clouds actually exist. It is simply unproven speculation. By comparison, there are some papers, which I have previously quoted, where the researchers in more than one country have been unable to find any evidence of such clouds of lice. However, there is a view that just because these clouds of lice have not been found does not mean that they are not there. Sadly, it is such views that simply prolong the debate about farmed-wild fish interactions. Maybe if other evidence supported the clouds of lice narrative, then there might be an element of doubt. However, any other evidence is also lacking so perhaps now is the time the idea that clouds of lice emanating from farms was filed away as another misconceived theory.

I had hoped that by now the delayed SPILLS report would have been published. This is supposed to include the outcome of plankton tows identifying lice larvae in the open sea. If and when this report is eventually published, we will finally get to see if such clouds of lice were actually identified or not.

What is interesting about SPILLS is that some of the data used in the project (not the plankton tows) is already available in the public domain. I have started looking at this data to make my own determination of the findings and whether they support the sea lice dispersal models that form the basis of the forthcoming sea lice risk assessment framework. Of course, I will share my future findings with readers of reLAKSation.


Science!: On their website, the Atlantic Salmon Trust say their aim is to transform science into action.

In the last issue of reLAKSation, I discussed the preliminary findings of the Atlantic Salmon Trust’s Moray Tracking Project. The AST place the greatest store on the science and in the past, I have been informed that any science must be published and peer-reviewed although I suspect that they are happy to include other science in their assessments as long as it is peer-reviewed. I certainly look forward to published peer-reviewed studies of both their Moray and West Coast tracking projects before considering whether their findings have any validity.

Until these papers are published, the AST have posted videos of the preliminary findings from both tracking projects. The most recent results were announced at a film night in mid-November held in London.  This was hosted by AST ambassador, actor Jim Murray who spoke about “the importance of putting scientific evidence over emotion” if a genuine future is to be secured for wild salmon.

Yet, just over three weeks later Mr Murray had been active on Twitter posting the following photo with the comment:

“Doing my bit in the local @Tesco who really shouldn’t be selling u this unhealthy, unsustainable, unethical muck. Do the planet and ur health a favour – choose something other than Atlantic salmon this Christmas.”


Mr Murray’s post was challenged by someone from the salmon farming industry and in a subsequent exchange, he said that what he knows about salmon farming comes from the biologists and scientists with whom he is in contact.

As Mr Murray copied his post to the AST, then they are clearly aware of his actions. How can the AST promote an ambassador who clearly puts his emotions over the science?

Whilst the AST like to promote themselves as a science-based organisation, the reality is that they are just as angling focused as the other representative organisations who prefer to deflect any blame for the poor state of wild stocks onto salmon farming, regardless of what the science actually says.


Tassie: Salmon Tasmania have produced the first in a series of short information videos titled – we need to talk salmon. This three-and-a-half-minute video takes a new look at some of the questions posed by those opposed to salmon farming. It is a refreshing look at some of the issues and worth a look. I would certainly encourage Tassie to produce more of this light-hearted look at the key issues. The first is available at


Testing times: Wild Fish Conservation have tweeted that the UK’s Environment Agency has released the 2022 fish counter data of the River’s Test and Itchen. According to WFC, preliminary data provides further evidence that urgent action is needed to save salmon on these rivers. The findings highlight that salmon populations are in crisis and that climate change and water quality conditions are considerable pressures impacting the adult salmon as they return to these rivers.

WFC just don’t get it. They are all too ready to blame specific issues relating to these rivers, warmer temperatures and questionable water quality. However, whilst cooler waters and better water quality may help in the short-term, but these fail to address the fundamental problem affecting salmon stocks from the south of England to the very north of Scotland. Numbers of salmon returning to all UK rivers are in decline and have been for over fifty years but no-one knows why. Instead, the so-called salmon conservation sector are fiddling around at the margins trying to find scapegoats to blame, whilst ignoring the wider picture. At least with the River’s Test and Itchen being in the southern part of England, WFC can’t cite salmon farming as the reason why these rivers are in crisis…yet!


Not just sea lice: The way that the wild fish sector moans on about sea lice on farmed salmon, even though it is more than evident that these sea lice are not responsible for the declines of wild fish, it is easy to forget that parasites do not just infest wild salmon and sea trout. The Times newspaper reports of concerns about the return of a flesh-eating parasite to Scotland. This is not a parasite that effects wild fish but rather us humans.

In fact, according to the TImes, a staggering 758 people in Scotland died from parasitic infections. This is up 5% on the previous total. The paper does not elucidate on which parasites are responsible for these deaths except to highlight that leishmaniasis, a flesh-eating parasite was responsible for one death. This parasite is usually spread by sandflies so is not indigenous to Scotland, but cases are re-emerging in Europe and the wider Mediterranean region. It could be that this single case is linked to travel or refugees. The last locally acquired cases in the UK occurred in 2005.

Whilst the parasite Leishmania may be rare, clearly other parasites are having a not insignificant impact on the Scottish human population. Yet, the wild fish sector would have everyone believe that sea lice are the most important parasite in Scotland, when clearly, they are not.