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reLAKSation no 1126

What they don’t tell you 2: In last week’s reLAKSation, I discussed the publication of the latest rod catch data for 2022, which I suggested had been posted without any fanfare. Unusually, the mainstream press has been devoid of any reference to the data at all. Having failed to publish their version of the data in their 2023 Annual Review as usual, Fisheries Management Scotland also failed to post news of the data’s publication on their website. The day after the data appeared, FMS posted a story about the ability of sheep to kill Giant Hogweed. Clearly, they consider this to be a much more important story than the state of salmon stocks in Scottish rivers.

This lack of publicity makes it seem to me that no-one from the wild fish sector wants to discuss this year’s data. In previous years, I have highlighted that there has been a significant discrepancy in catch data reported by FMS and that from the Scottish Government, even though it comes from exactly the same source. Maybe, they are hoping that if they play down the data, it won’t get discussed.

One of the reasons why I look at the data is that it shows that the claims made against salmon farming’s impact on wild fish stocks is highly overstated. As I showed last week, this year’s data is no different.

Although there has been at least five months between the end of the fishing season and the publication of the data, the published report provides only cursory analysis of the catches. Last week, I compared the salmon catch from around the salmon farming area with that from areas where there are no salmon farms and showed that the picture for salmon is relatively much worse on the east coast than on the west.

This week, I have analysed the stock components. This is the breakdown of large salmon (Multi Sea Winter – MSW) and grilse (One Sea Winter – 1SW) fish. Marine Scotland Science record the numbers and weight of these fish but don’t seem to invest much time in finding out what this data tells us.

In their short report, MSS publish a graph showing that MSW fish described as spring salmon have been in decline for many years whilst, until recently, summer and autumn fish (both MSW and 1SW) have increased. In fact, the graph (blue line) looks remarkably similar to the one showing the total catch. This is not surprising since summer and autumn MSW and 1SW fish account for the majority of the catch.

It is interesting that MSS select out just Spring MSW salmon from the other fish. Is this a biological issue or because these are the fish that are most highly prized by anglers and there have been progressively fewer of them for anglers to catch. Could it be that this is the only reason that they receive special attention?

Whilst MSS focus their attention on Spring MSW salmon, I have analysed the specific trends for both large salmon and grilse regardless of whether they are caught in the spring, summer or autumn. It doesn’t take much time to analyse the full data set and arrive at the following graph:

Irrespective of the longer-term declines in the number of salmon returning to Scottish rivers from their marine feeding grounds, there are very clear differences in the fate of large MSW salmon and smaller 1SW grilse in Scottish rivers. Over the last seventy years, large salmon catches have been in decline, whilst numbers of smaller grilse have been increasing.

This comes as no surprise because not only did Dr Ronald Campbell, now retired from the Tweed Commission, highlight such changing trends going back to the 1700s on a YouTube video,  but I published a peer-review paper last year which looked at these exact same trends in the north west highlands and across all of Scotland. Although the paper did not specifically mention sea lice, I have asked the question widely as to how grilse catches could have increased if sea lice from salmon farms were actively killing wild salmon in the areas around salmon farms. I am still waiting for an answer, yet this remains an extremely valid question. How can grilse numbers be increasing around salmon farms, when sea lice from the very same farms are blamed for declines in wild fish numbers?

Irrespective of the question about west coast salmon and sea lice, the fact that data showing the changing fortunes of MSW and 1SW salmon has not been explored, demonstrates that the Scottish Government has been taking a blinkered view of salmon catches for many years. It is not surprising that they no longer want to shout about the limited amount of information they produce.

I would remind readers that the data is supplied to Marine Scotland Science by river proprietors from across Scotland. This is not my data. I have simply added up the numbers which anyone else could easily do, but no-one else seems in anyway interested.


Canadian evidence: Earlier this month, Wild First Canada published an open letter to the Globe and Mail. Seemingly the paper had published an article from pro-salmon farming interests in which it was stated that DFO science ‘proves’ that farms are operating in a sustainable way that poses minimal risk to wild salmon.

In this letter of response, Dr John C. Madden, writes that he is not aware of any proof. He continues that it is likely that many if not all of us would change our minds about the problems with net pen aquaculture if any proof could be produced. After writing that there is substantial information to support the claim that net pen farms harm wild salmon, he says that if there is proof there is no risk of harm it would make a huge difference in the way that net pen farms would be treated. However, he ends by saying that if there is no proof then don’t waste his (and other’s) time.

There is a link to a detailed report on risks from open net salmon farms written by the Pacific Salmon Foundation, of which the first is sea lice.

This report begins by stating that there is an established body of evidence that links sea lice with impacts on salmon globally, citing two papers. The report continues: ‘In BC, most evidence of the impacts comes from the Broughton Archipelago where sea lice from salmon farms have been associated with reduced survival in pink and coho salmon. Three papers are cited for this statement. The report also says that in contrast chum salmon in the Broughton do not appear to have declined as a result of sea lice from salmon farms. For this statement, one paper is cited. This makes a total of six papers that are cited as showing sea lice from salmon farms have an impact on wild salmon, but not chum.

There is a common thread between all six papers, and this is that they are all co-authored by Martin Krkosek who is described as working in fundamental and applied ecology. He is also a director of the Salmon Coast Field Station who describe him as using mathematical tools in his work by developing theory and synthesising datasets to address important policy relevant questions.

I don’t know which datasets Dr Krkosek has analysed or synthesised, but the Salmon Coast Field Station have been collecting sea lice data from around the Broughton Archipelago since 2001. The link to the data can be found in their 2022 sea lice report. This amounts to 47.473 fish consisting of both pink and chum salmon.

The analysis of the sampled fish carried out by the Salmon Coast Field Station is limited primarily to measurements of prevalence and abundance which they plot for every year. What these measurements do not consider is the spread of lice infestation across the whole dataset. This provides a much clearer picture of how sea lice impact on wild fish, regardless of their origin.


What this data shows is that 60% of the salmon sampled are lice free.  About 20% have one louse, 10% have two, about 4% have three and 2% have four. Fish with more lice are extremely rare despite the images distributed by those fighting against salmon farms. In addition, the majority of these infested fish are carrying young lice stages, not the adult stages often shown.

If 60% of the fish sampled are free of lice, the risk is clearly not as high as the critics maintain. Whilst critics suggest one louse can kill a young wild salmon, the reality is that there is no benefit to the lice if it kills its host.  They must be able to carry at least one louse, otherwise the lice would not survive too. Whatever evidence the papers cited by the Pacific Salmon Foundation provide to implicate salmon farms in the demise of wild salmon, the data collected by the Salmon Coast Field Station with whom Martin Krkosek has had a long-time association, tells a very different story. I await with interest to hear the views from Martin Krkosek, the Salmon Coast Field Station or Wild First Canada.

Interestingly, the graphs for pink and chum salmon extracted from this data are remarkedly similar.


This begs a critical question. According to the Pacific Salmon Foundation, Martin Krkosek says chum salmon in the Broughton’s are not affected by sea lice from salmon farms. If chum salmon are not affected, then neither are pink salmon, as the pattern of infestation is almost identical for both species.



Just an observation:  The Scottish Green party recently issued a press statement in which they argue that Scotland’s creelers and divers must be protected from big business.

Speaking in a debate in the Scottish Parliament, the Green Party’s coastal spokesperson said that big business in the form of trawlers and dredgers are not at one with nature and are destroying the seabed. In addition, these trawlers and dredgers tend to be based outside the local communities, who might otherwise benefit from low impact creeling and diving.

The Greens said that other politicians were whipping up scare stories against marine conservation by comparing the introduction of HPMA’s to the Highland Clearances. However, the introduction of HPMA’s is unlikely to help the creeling and commercial diving sector since all activities would be banned within these new areas.

If the Greens really want to help creelers and divers and still protect the marine environment from trawling and dredging, then a reintroduction of the three-mile fishing limit would be far more beneficial than the introduction of HPMA’s since this would effectively ban large fishing boats from coastal waters and allow the smaller inshore fishing fleet to flourish.

There is plenty of scientific evidence that stocks of marine fish collapsed in inshore waters after the three-mile limit was removed in 1984. What is more, my own research has shown that it was the removal of the three-mile fishing limit rather than salmon farming, that caused the collapse of the Loch Maree sea trout fishery.

Perhaps, the reintroduction of ta three-mile fishing limit might better help the recovery of wild fish in Scottish coastal waters than the blinkered attempts to shackle the salmon farming industry.

The Greens also published a second release in which they applaud the success of the Lamlash Bay ‘No Take’ zone which they say has had a positive impact on fish stocks and nature replenishment. The Greens say that this is an underwater triumph with clearer and healthier waters, a thriving ecosystem and return of nature. It shows what a positive impact ‘No Take’ zone can have on local communities.

It is easy to ignore the fact that a salmon farm has been located in Lamlash Bay since 1988. The Greens have listened to a vocal minority about the impacts of salmon farming saying that salmon farming has wrecked the coastal environment, yet they seem to ignore their own statement that Lamlash Bay has clearer and healthier waters and a thriving ecosystem, despite the close proximity of a long-established salmon farm.