Sea lice science 1: Back in June, Wild Fish wrote that another academic paper had been published highlighting the damage being caused to wild salmonids by sea lice emanating from fish farms. The paper said that the effect of sea lice is larger than the average effects between 2001 and 2019 and is also larger than the average effects reported in earlier randomised control studies.
When I looked at the data cited in the paper, there were some basic errors such as the data point for the River Erne was incorrectly reported. Clearly, the paper had not been proofed, and it is also worrying that this glaring error was not picked up in the peer review process.
Now the authors have issued a correction in the Journal of Animal Ecology. Seemingly, the main error was not an isolated incident. Mobile lice numbers for 2009 at Burrishoole were incorrectly entered as 3.91 but should be 3.13. The authors claim this was a typo. In addition, the forest plot was incorrectly labelled.
In the published correction the authors say that the rectification of the data means that the returns show a marginal increase from 18 to 19.2%, but they say that this does not affect their conclusion which remains valid and statistically supported. However, if I remember my calculation of the data, confirmed by a friend from the US who reached the same figure, was that the impact was actually much less than these authors claimed. I used a simple calculation whereas the authors of this paper used one that was based on complex statistics. I was once told that if you have to reply on complex statistics to demonstrate an effect, then the effect isn’t worth consideration.
The paper is authored by four scientists. I would presume that they have all read the paper before it was submitted and again before it was published. Yet none of them picked up the errors. I can only wonder how many other errors might be buried deep in the complex statistics that were used in this meta-analysis.
In my experience, it is only the headline findings of most published papers about the alleged damaging impacts of sea lice that are highlighted either in the media or by critics. Unsurprisingly, the detail is ignored, and thus the headlines are taken at face value and assumed to be correct, Sadly, this is not often the case with the detail telling a different story. Another example is also discussed later in this issue of reLAKSation.
How often are we told that peer reviewed papers published in a top journal should not be questioned. My view is that in the sea lice world, everything should be questioned. Unfortunately, it now seems that many researchers don’t like to be questioned at all. Attempts to contact author of the original paper remains unanswered.
Sea lice science 2: Another paper has also come to my attention. The title is’ What are the effects of sea lice on wild and farmed Pacific and Atlantic salmon? A systematic map protocol’. This is a collaboration between DFO in Canada and the Canadian Centre for Evidence Informed Conservation at Carleton University. The paper attracted my attention because I recognised the names of some of the authors, who were recruited by NASCO to help undertake the literature search for the work intended to demonstrate that sea lice were damaging wild fish populations. I did have some contact with the group who said that they knew nothing about sea lice. It seems that in addition to NASCO, DFO also wanted help to develop a knowledge synthesis to ensure a full understanding of the host parasite relationship. A knowledge synthesis is a transparent and reproducible methodology that formally identifies, appraises and integrates existing research findings to answer a specific question, inform best practices and identify gaps in knowledge.
However, the NASCO work has shown that such synthesis suffers the same problem as the modelling of sea lice. At some point assumptions must be made in the process and the outcome will be inherently affected by these assumptions. For example, the paper focuses on studies that include the genera Lepeophtherius, yet from my perspective, most of the most interesting aspects of sea lice research come from general parasitology rather than sea lice work itself. In addition, the knowledge from looking specifically at sea lice will result in many papers on alleged damaging impacts of sea lice on fish because that has been the specific research focus. The fact that the research team do not have knowledge of sea lice interactions will further undermine their conclusions.
In their final discussion, the authors say that the proposed systematic map will be used to determine whether there is sufficient evidence to further investigate possible effects of sea lice from net pen salmon farms on wild Pacific salmon. It seems to me that this is a risky way to undertake future research. Meanwhile the evidence from thousands of wild Pacific salmon has shown that the impacts of salmon farms is in fact minimal, borne out by science that many choose to ignore.
Sea lice science 3: After a gap of three years, the international sea lice conference Sea Lice 2025 is returning, and this year will be coming to Puerto Varas in Chile at the end of November. One Norwegian researcher has suggested that this would be a good place to discuss any new science rather than be willing to sit down and review all the issues either in Norway or Scotland.
The problem, bar the huge expense which I am sure Norwegian Institutions are willing to cover to allow their researchers to attend, is that the programme depends on the topics covered by submission so as there will not be a deluge of presentations covering the flaws to the established narrative, any such submissions are likely to be lost amongst more specific topics. The topics suggested by the organisers include:
- Sea lice biology and ecology
- Modelling and epidemiology
- Pharmacological treatments
- Non-Pharmacological treatments
- Resistance
- Genetics and genome
- Fish welfare
- Wild fish interaction
- Management and regulations
The second problem is that any presentation is limited to 15 minutes with just 5 minutes of questions. Instead, what is really needed is a different conference/seminar which specifically looks at how the established narrative fails to reflect what is really happening between sea lice, salmon farms and wild fish. Sadly, the existing scientific community don’t want to discuss such issues, a point made in a letter to the journal Reviews in Aquaculture.
Following the publication of a paper by Van Ness, Imsland, and Jones which reviewed factors affecting the salmon farming management system, the Sea Lice Expert Group have written a response to the journal in which they say that that they acknowledge that the current assessment has many uncertainties which is why they welcome constructive critique. Unfortunately, they do not see suggestions that their assessment is flawed as constructive, so they are not interested in hearing the any such contribution. They say that the Expert Groups methodology is continuously developing and improving in response to new knowledge and constructive critique as exemplified by the review by International Evaluation of the TLS (although that was four years ago).
However, the recommendations of that group, whose composition was somewhat of a puzzle, were very generalised so it is difficult to see how their suggestions have been reflected in the current assessment process. The third of 15 recommendations has certainly been ignored. They recommended that the composition of the Expert Group should be given further consideration and that expertise in areas such as scientific epistemology, knowledge inclusion and science communication should be added. I would also add that there should be industry representation on the group. There are certainly highly academic qualified people working in the industry who are more than capable of contributing to the assessment. Perhaps the Expert Group aren’t so keen on some real-world experience in their midst.
Anyway, in my opinion, the letter from the Expert Group as published in the journal, together with a response from the authors of the original paper amounts to nitpicking various issues raised such as whether lice larvae production is overestimated rather than discuss more important questions such as where do these lice larvae go because it is clear that they don’t spread out through the fjords as the Expert Group suggest.
Is this science: A new paper from NORCE commissioned by the NALO sea lice programme has looked at the survival of sea trout in the area around Herøysen in Western Norway
The team PIT tagged sea trout over two years and then in subsequent years detected any surviving fish using a PIT Tracking System set into a local river or by using a handheld detector for any fish caught in traps. Based on the numbers detected, the team attempted to evaluate the survival of the sea trout over time. Using modelling, they estimated that increasing the lice load from 0 to 1 lice per gram reduced survival by 78% in 2020 and 58% in 2021. Such potentially low survival certainly fits the narrative promoted by the NALO programme that sea lice are negatively impacting the stocks of wild sea trout. However, there is a major flaw in this research.
The team have no way of knowing whether the fish that they PIT tagged but never subsequently redetected had:
- Died as a result of the insertion of the tag
- Moved away from the research area
- Returned to freshwater.
Just because they did not detect the tagged fish does not mean that they died. Sadly, if sea lice researchers are so invested in the established narrative, then their only conclusion will be that the fish must have succumbed. Yet, the evidence collected over many years shows that most sea trout are free of lice so cannot have succumbed to the parasite. Unfortunately, the fish collected by the researchers are not representative of the wider stock because most were infested with sea lice. This is the inevitable consequence of using traps to collect fish as traps tend to attract the less robust fish. By comparison, strong healthy fish tend to avoid the traps.
Evidence now suggests that numbers of sea trout from around the river Etne have significantly increased this year. This is contrary to the general findings of this new study. The expert group which determines the impacts of sea lice using NALO data have made it clear that they only want constructive contributions. They are not interested in anything that might contradict their view of sea lice impacts. If this is the new science that interests them then God help the salmon farming industry.
Interestingly, whilst the abstract of the paper states that this is the first study to demonstrate a statistically significant association between the survival of individual trout and their parasite loads, the following paragraph is buried at the end of the discussion section:
“the absence of detection by the antenna does not necessarily indicate mortality; rather, it may reflect a decision by the fish to forgo further marine migrations. This distinction is crucial to accurately interpret our findings, because it underscores that non-detection could be due to behavioural choices rather than a direct consequence of mortality. As a result, our estimated effect of salmon lice on survival may be overestimated if non-detection is interpreted as mortality when the fish has actually survived but chosen not to migrate”.
The reality, based on other evidence, is that the suggestion that the mortality may have been overestimated is something of a massive understatement. Their flawed assumption is that sea lice are negatively impacting wild fish stocks but as I have repeated many times, the science promoted through NALO is highly flawed.