Risk report: I shall discuss the implications of the latest Institute of Marine Research (IMR) Risk Report which was released last Wednesday in the next issue of reLAKSation. In my opinion, the greatest risk to the environment, fish welfare and the salmon farming industry in Norway is the Institute of Marine Research. More in the next issue.
Everyone knows: In the last issue of reLAKSation, I discussed the findings of a paper by Peder Jansen and others that the Sea Lice Expert Group say is further proof that sea lice have a negative impact on wild salmon.
The paper was also mentioned in a commentary from Pål Mugass of Norske Lakseelver, the river manager’s organisation, in which he says that the paper confirms the connection between seal lice and wild fish numbers, and he concludes that the salmon industry must work harder to protect wild salmon from sea lice. I responded to the Mugass commentary saying perhaps he should focus more on what his sector is doing to protect wild salmon, than worrying about the salmon farming industry. After all, the latest catch data shows that anglers caught and killed 4,670 large salmon and 22,140 sea trout. In 2019, VRL estimated the impact of salmon farming on wild salmon smolts to be 39,000 fish although VRL are unable to confirm that any of these fish actually died or that they died from sea lice.
Anyway, in response to my comments and a separate commentary posted on the Aquaqblogg website, Dr Jansen said that it is good for work to be criticised but then went on to criticise our criticism. I too welcome such debate but I would rather it took place in a debating chamber rather than through the pages of the media. Sadly, FHF who funded the Jansen research didn’t want such debate to take place at their sea lice conference which was held at the beginning of February. This was a missed opportunity.
Dr Jansen says that the distrust of modelling is interesting but irrelevant in the context of his work, which is incorrect. Truthfully, I don’t distrust models, I just want to be certain that whatever they predict reflects what happens in real life.
Dr Jansen continues that it is incomprehensible how I can so emphatically refute that there is any connection between lice in farming and the impact on wild smolt. He continues ‘Everyone knows that lice are …’ This couple of words highlights all that is wrong with sea lice science. The alleged impacts of sea lice on wild fish have been repeated so often especially by the angling sector that they must be true, as ‘everyone knows’.
Interestingly, Dr Jansen and I corresponded before his commentary appeared in which I pointed out that evidence from Scotland did not support the view that sea lice had a negative impact. I sent him a couple of graphs to which he did not reply.
Deadly: If I was given £3.4 million to research the impacts of sea lice on wild fish, I would certainly spend money on investigating if sea lice larvae can be found in the numbers and locations predicted by the various sea lice dispersal models because so far there isn’t any evidence that the models are a true reflection of what happens in the wild. I would also investigate if the sampling conducted to determine the level of infestation of wild fish by sea lice really reflected the infestation of the wider population. These are really key questions which the scientific community currently choose to ignore.
Unfortunately, I have not been given £3.4 million to research sea lice but a group of scientists led by the Institute of Marine Research was given this sum of money in 2024. The first pieces of work from this project (Hit Lice) are now starting to appear as reported by Salmon Business. An article published at the end of January asks ‘Are salmon lice deadlier to wild salmon than we thought?’ It seems that the aim of the Hit Lice project otherwise known as ‘the Hidden Toll of Sea Lice’ is to portray sea lice as the greatest threat to wild salmon even though the evidence now shows that sea lice are being unfairly targeted in order to provide continuing work for the scientific community.
The new work was conducted to validate previous research on the effects of sea lice which have been largely based on farmed salmon or offspring of wild fish raised in aquaculture facilities. According to researchers, the artificially raised fish differ from truly wild salmon particularly in terms of weight and condition.
According to Salmon Business the findings showed that wild salmon exposed to sea lice had poorer growth and a lower condition factor than fish without lice. The researchers conclude that mortality rates in the wild are likely to be higher than those observed in the experiment.
Fortunately, the work has already been published in the ICES Journal of Marine Science (as part of a PhD thesis) so it is possible to dive deeper into the findings. The paper describes two experiments with fish in 2023 and 2024 (which begs the question how this work was funded by a project that did not receive funds until 2024).
In May 2023, 26 smolts were trapped from the Etne river and held locally for 2-3 days before being transported (over 6 hours) to the research tanks holding 6-7 fish. Over a period of five days the salinity was increased to full strength sea water after which the fish were left for two days before being infected with sea lice. The infection method was to reduce the water to 10cm depth and then sea lice were introduced and the fish agitated to ensure maximum contact. After 20 minutes, the water flow was resumed. The lice were stocked at 1.1-1.3 g L-1.
In June 2024, 43 smolts were trapped from the Dale River and were transported (2 hours) to a single research tank and the salinity increased over the following 4 days. The fish were then left undisturbed for a further 4 days before being transferred to separate infection tanks where they were exposed to either 1.75 or 3.63 g L-1 sea lice infection. However, unlike 2023, these fish suffered early mortality with five fish dying between 9-11 days after transport and a further 15 fish exhibited wound and tail rot and were removed leaving just 21 fish for analysis.
It appears that at the end of the 2023 trial, no fish had actually died, whilst of the 21 fish in 2024, 11 died. In addition to those fish that died before the sea lice infection.
The paper concludes that sea lice pose a significant risk to wild salmon when exposed to elevated levels of the parasite when they enter the marine phase. Given that no one has actually found elevated levels of sea lice in the fjords, it is unclear whether this conclusion can be drawn. There are increasing numbers of papers that now question whether laboratory studies can be used to evaluate infection pressure of parasites such as a paper by Chapman et. al. (2021) Disease ecology of wild fish in the Canadian Journal of Fisheries and Aquatic Sciences in which they say that applying lab-based work to wild fish populations is ‘precarious’ because transmission pathways do not reflect natural environment.
From my perspective, in this example, taking wild fish that have lived in the natural environment for perhaps a coupe of years and then exposing them to tank conditions in which salinity is changed and then infecting the fish is bound to be stressful leading to an unrealistic picture of infection. It seems that the Hit Lice project is now extending this work to large samples. Instead, I would be asking where are these elevated levels of sea lice that the experimental fish succumbed to be found in the real world. That is a much more interesting question than whether wild fish die when kept in a laboratory setting.
Google Gemini science: I gave up following social media some time ago because the negatives outweigh any potential benefit however, recently I have been alerted to a scientific hypothesis that is now being promoted on Facebook. The author is a Mr Fraser who can claim fame by catching the first salmon of 2025 from the River Moriston estuary on January 20th that year.
Mr Fraser’s foray into science began after reading ‘the brilliant Alexandra Morton book “Not on My Watch” where she described how sea lice levels on juveniles dropped dramatically when the salmon farming industry starting using Slice Emamectin Benzoate in the early 2000s, lice levels were high again in 2015’ (sic).
According to Mr Fraser, this was the last piece of the puzzle to helping explain why wild salmon populations in Scotland were in decline. Sea lice had built up a resistance to Emamectin benzoate and thus the inability of the salmon farming industry to control lice has had a devastating effect on wild salmon populations across Scotland.
To confirm his theory, he turned to an expert source – Google Gemini as can be seen in the following image:
The response to the question (in blue box) includes the suggestion that there was a window of effective sea lice control. When Gemini created a graph of this sea lice window in relation to salmon catches from the east coast river Dee, the result is shown below:
This implies that there were increased catches from the River Dee after 2000, but subsequently they declined as sea lice grew out of control due to the increasing ineffectiveness of Emamectin. This graph looks convincing but there are significant questions about its reliability. Firstly, the graph needs to be put into the context of long-term rod catches as shown below. Seemingly Mr Fraser’s theory is that salmon catches have been in decline because the salmon industry could not control its sea lice numbers. Yet in 1982, salmon production had only reached 1,000 tonnes and clearly, the river was in decline long before then. More recently, Mr Fraser seems to regard the increase in catch around 2000 as when lice numbers were managed due to the use of Emamectin and then the subsequent collapse was due to the build up of resistance.
However, what Mr Fraser ignores, or at least AI does because the question was not asked, is that rods were not the only form of exploitation affecting the river Dee as shown by the following graph.
When total exploitation is considered, Mr Fraser’s theory goes out of the window because the claimed increase simply didn’t happen. The increase in catches observed by Mr Fraser is more likely the consequence of the closure of nets leaving more fish to reach the river.
Finally, Mr Fraser also fails to take into account that Emamectin was not the only treatment available to reduce lice either before or after it was introduced. In addition, whilst sea lice did become resistant, a more managed use in combination with other methods of lice control mean that Emamectin remains within the armoury of treatments to control sea lice on farms.
Of course, the main argument against this theory is that the east coast does not have any farming activity. However, Google Gemini has picked up the modelling commissioned by Wild Fish that suggests there are plumes of sea lice heading south towards the east coast rivers and produced the following image.
Yet, as I have repeatedly highlighted, no-one has yet found any sea lice in any water body that reflects the image of the model. In fact, the Wild Fish model appears to predict concentration of lice larvae of less than 0.1/m3. This is not the sea lice soup that critics often portray. I am also remined that prior to 2012, Wild Fish claimed that east coast rivers had healthy catches because there was no impact from salmon farms. The subsequent collapse of east coast salmon catches forced a change of argument with blame directed at salmon farms on the northern isles, even though many of these farms had been in operation since the 1980s. Its no wonder that Wild Fish refuse to discuss such issues.
Returning to Mr Fraser, his Facebook page includes about twenty graphs of different rivers, not just in Scotland, but also in Canada and Norway, that have been affected by the Emamectin effect. Many of these graphs can be immediately disproved because the catch data portrayed bears little resemblance to the official catch data, but I will give it to Mr Fraser that he is extremely focussed on his theory. I have looked through the many comments he received, mainly congratulating him on his science but there have been others that highlight clear errors in the data, all of which he chooses to ignore.
I have included Mr Fraser’s work in my commentary because it does raise the question about the use of AI in the continuing crusade to demonise the salmon farming industry for the ongoing declines of wild salmon. By comparison, any such data discussed by the industry is always dismissed as tobacco industry type propaganda by the angling sector. Of course, as everyone knows, angling has no impact on declining wild salmon numbers!
Finally, Mr Fraser’s postings are interesting because he posts comments from Google Gemini as if they are his own, but he forgets to change the words ‘your’, which is repeated regularly, to ‘my’. As he posts the links to the Google Gemini exchanges, it is possible to see how his theory has developed. Some examples which make interesting reading include:
https://g.co/gemini/share/5af5f9390849
https://g.co/gemini/share/6d88430d6f4b
https://gemini.google.com/share/7ece1d4e65b5
Postscript: I was told that Mr Fraser’s latest post makes even more interesting reading. Seemingly, sea lice nauplii can travel 50 km before developing into the infectious stage after which at 9oc they have 16 days to find a host during which they can cover 215 km but with a steady Northerly wind the distance increases to 350 km. Hence, sea lice hatched in Shetland can reach the Moray Firth or the Aberdeenshire coast whilst still infectious.
It’s a pity, there is no sea lice conference on the horizon because I would readily invite Mr Fraser to share his theories with the industry.