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reLAKSation no 1050

Sea lice science: At the beginning of October, Fish Farming Expert wrote about the publication of the Scottish Government response to the Salmon Interactions Working Group report. Their response begins with the statement that ‘Based on the international and domestic scientific evidence base available, there is a risk that sea lice from fish farm facilities negatively affect some populations of salmon and sea trout in areas of Scotland. The published science is summarised by Marine Scotland’. (,reduce%20interactions%20with%20wild%20salmonids.)

Except, the international and domestic scientific evidence presented by Marine Scotland doesn’t actually support the claim that there is a risk that sea lice from fish farm facilities negatively affect some populations of salmon in areas of Scotland. (I have omitted the words sea trout because 1. This is a response to the Salmon Interactions Working Group report and 2. If sea trout are included, then the discussion would be very different).

I have repeatedly written that none of the observational data provided by Marine Scotland provides any evidence of the negative impact of sea lice. However, Marine Scotland Science (MSS) have never been willing to explain how they have reached their conclusions.

I have also discussed the experimental findings they present in previous issues of reLAKSation; the last time as recently as mid-November. MS say in the summary of the science that:

“Multiple studies conducted in Ireland and Norway using artificially reared salmon smolts have found that treatment with anti-sea lice agent increases likelihood of fish survival to return as adults (Vollset et al. 2016). The assumption from this is that protection of the emerging smolts from sea lice acquired in the coastal zone enhanced the ‘at sea’ survival. There is a great deal of year-to-year and site-to-site variation in the magnitude of such an effect; the reduction in numbers of returning salmon associated with lice in untreated smolts is in the range of 0-39% (Jackson et al. 2011; Krkošek et al. 2013; Skilbrei et al. 2013; Vollset et al. 2016).”

This statement is misleading because 1. Only two of these studies actually undertook experimental studies whilst the others simply reanalysed the original data applying different statistical analyses. This is because they held the preconceived idea that salmon farming was responsible for declines of wild salmon which the original data did not support. 2. The aim of the Jackson paper was to measure the marine mortality of wild salmon resulting from sea lice infestation. However, the MS summary discusses survival rather than mortality. This is misleading because the mortality concerns very large numbers of fish whilst survival relates to just a few. When percentage change is applied to these few fish, the percentages can be very large. For example, the difference between whether 4 or 6 fish survive is 33%, whereas the difference in the equivalent mortality is very small, for example, between 94 and 96% which is just 2%.

Unfortunately, MS have opted for the survival approach stating reductions of up to 39% and this has been taken by many as sea lice causing a mortality of 39 out of every 100 smolts. However, this is not the finding of the Jackson study.

After I mentioned the Jackson paper in reLAKSation no 1046, I heard from one of my Canadian correspondents drawing my attention to a blog posting he had written in 2013 about the same confusion that some wished to impart on the original experimental study. I believe that the comments made then are worthy of a revisit in this issue of reLAKSation:



The following is a guest post by reader Bob Milne, who is writing in response to a study published in November 2012.

by Bob Milne

Many people believe farm-origin sea-lice are to blame for reduced wild salmon stocks in several salmon farming areas of the world.

This belief is based on numerous articles, primarily in the media, which have selected only certain aspects of on-going research and sensationalized the somewhat dubious results. This article looks at one instance of this manipulation of the data and facts relating to the fish farms of Ireland and Norway. It is shown that the research cannot draw any conclusions about wild fish, since no wild fish were used in the study.

It is important to understand that relatively little is known about the reproductive cycles of the species of louse at the heart of the issue.(Lepeophtheirus salmonis). So let’s focus on what we do know.

Yet another sea louse study makes bold claims that the data doesn’t bear out.

In order to take a hard look at what is really known we must ignore the media and focus attention on the research papers and the scientific reviews they quote and compare them to the accompanying press releases, conclusions, and recommendations. This comparison will illustrate just how highly politicised the issue is. All press releases and media pieces are only telling part of the story, commonly omitting inconvenient truths that spoil the story line. Public opinion is thus formed by how the data is interpreted and which conclusions are drawn rather than by the methodology or data found within the study. The scientific method and data alone should allow the reader to draw their own conclusions, if indeed any may be made.Research money is scarce unless there is a cause supported by the public and grant donors that seems to have some urgency. Today the popular topic is: “farm origin sea-lice killing wild salmon.” There have been many research papers and reviews condemning the salmon farming industry of late. Every week seems to bring more press releases and alarming headlines quoting these papers from Canada to New Zealand, Scotland, Norway and Ireland. One would gather from the media that farm origin sea-lice are polishing off all the wild salmon in the world. But when you hunt down the quoted research papers and reviews of the scientific literature and their references, there is a much different story to be told.

Let’s take the recent review and press release from the prestigious St. Andrews University as case in hand. The research paper published Nov. 7 2012 can be found here.

The lead author is the same anti-fish farming activist ( Dr. Martin Krkosek) who has drawn his conclusion about sea-lice as far back as 2004 and has been successfully searching hypotheses and funding ever since. And since the conclusion has already been found (salmon farms are bad) there is endless hypotheses and funding flowing to the activist hero scientists of our day.

The paper is a meta-analysis of the data from six very different studies done in Ireland on fish returning 2002-6 and in Norway on fish returning between 1996-8. One of the many things Dr. Krkosek doesn’t talk about nor mention in the press release is that all of the fish involved in his review are hatchery origin fish bred for over 30 years for ranching purposes. They have been cultured for at least a year in fresh water then approximately 50 per cent of the subject fish were treated with proven anti sea-lice treatment of either emamectin benzoate or, Substance Ex (Alpharma) which involves a topical bath treatment previous to release .They were for the most part released in large numbers although at various times but nevertheless very little can be inferred (if anything) towards wild fish from this data.

Upon close inspection of the data used for the study one will notice that over 63% of the 283,347 fish released (181,271) were part of a detailed study in Ireland.

The lead author is D. Jackson from the Marine Institute, Rinville, Oranmore, County Galway, Ireland. His conclusion is very different from that of Dr, Krkosek, as exemplified in the following quote. From the paper titled “An evaluation of the impact of early infestation with the salmon louse Lepeophtheirus salmonis on the subsequent survival of outwardly migrating Atlantic salmon, Salmo salar L., smolts:”

The results to date show a strong and significant trend in increasing marine mortality of Atlantic salmon originating in the study area. They would also point to infestation of outwardly migrating salmon smolts with the salmon louse (L. salmonis) as being a minor and irregular component of marine mortality in the stocks studied and not being implicated in the observed decline in survival rate. (Jackson et al, 2012)

There are two very important distinctions between the analysis in Jackson’s original study and the meta-analysis of the same data by Dr. Krkosek et al.

Firstly, the work of Jackson is objective. Because the source for the theoretical sea-lice of unknown species is indeed unknown, the source is responsibly not mentioned.

Secondly, considering the subject fish are all hatchery raised ranch fish and have been bred as such for at least 30 years, Mr. Jackson makes no reference to wild fish in the paper. The research has absolutely nothing to do with wild fish or farm fish so in the name of good science, it also requires no mention.

In contrast, the Krkosek paper contains the word “wild” eleven times and salmon farm/aquaculture no less than fourteen times, despite his meta-analysis having absolutely nothing to do with wild or farmed fish. For example, a quote from the recent St Andrews press release leads one to believe that there have been clinical studies on wild salmon when the research in fact had no clinical studies and was not done on wild salmon. No new data was brought forth.

“Our research is similar to clinical studies in medicine – except that wild fish are the patients.”­ – Professor Martin Kkosek

In addition, the most important discovery in the Jackson trials is the strong and significant trend in increasing marine mortality of the hatchery Atlantic salmon originating in the study area regardless of whether or not they have been treated for sea lice, as illustrated in the graph below. This graph represents over 63% (181,211 fish) of the data used by Dr. Krkosek for his review yet displays approx. 1.5% higher mortality in the untreated fish as opposed to the 39% claim we see in the headlines.

So it follows that if farm-origin sea-lice were to blame for increased mortality of wild/hatchery fish we would see a corresponding increase in survival of the treated fish in relation to the untreated fish throughout the study period (diverging lines) or at least notable disparity between the two lines on the graph above in relation to lice loads at the salmon farms. This notable trend strongly suggests no effect of farm-origin lice on the mortality of ranch/wild fish in the area but as this trend contradicts the story line of Dr Krkosek’s paper; it is not mentioned.

Dozens of Published articles by Dr. Krkosek on sea-lice and disease all draw the same conclusion from his mathematical models. Many are simply re-hashing of old data by reviewing it and coming to the same conclusion (salmon farming is bad), without any conclusive evidence. The names appearing as co-authors are a virtual who’s who of salmon-farm hating activists posing as impartial scientists to line their pockets and further their anti- farm agenda.

It is not an accident that we get alarmist headlines like “salmon farms kill 39% of wild salmon” or “massive extinctions of pink salmon from fish farm sea-lice” that quote papers by Dr. Krkosek and his ilk. There are thousands of media outlets and blogs dedicated to the purpose. The press release from St Andrews mentions wild fish 3 times and salmon farms twice. They quite craftily wrote it up that way in the press release, knowing journalists and editors readily omit the cans, coulds, mights, and maybes. (Note: The original press release follows the end of this commentary)

The fact is there is no known mechanism for determining the origin of a sea louse nor to distinguish farm-origin from naturally occurring animals and very little is known about background levels of the copepods that infect the farm fish or the wild/ hatchery fish in the first place.

The modelling that Krkosek and his colleagues use is only one tool in an arsenal that should be used to further our understanding of sea-lice /salmon interactions, but instead is being used as a weapon to unjustly condemn the salmon farming industry.

The topic requires a detailed understanding of the complicated host-parasite relationship at hand. The model is taken from epidemiology and crudely tweaked to apply to sea-lice transmission dynamics. From a rational perspective one can’t help but think that if this modelling did not indicate that the sky is falling then it would serve no purpose at all. Thus it follows that the mathematical models will continue to condemn salmon farming for the foreseeable future as long as the inputs to the model and the press releases are controlled by the same activists, scientists, and researchers.

A quote from the innovative neuroscientist ‘Ramachandran’ famous for his simple yet elegant science on brain plasticity:

“I have a disdain for complicated fancy equipment because it takes a lot of time to learn how to use, and I’m suspicious when the distance between the raw data and the final conclusion is too long. It gives you plenty of opportunity to massage that data, and human beings are notoriously susceptible to self-deception, whether scientists or not.”— Ramachandran

Here is one of many criticisms from respected federal fisheries scientists Brian E. Riddell et Canada regarding Krkosek’s extinction predictions from a 2007 paper titled “Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon:”

 Krkosek et al. overstated the risks to wild pink salmon from sea lice and salmon farming. Furthermore, their predictions are inconsistent with recent observations of pink salmon returns to the Broughton Archipelago. Their alarming statements of extinction of pink salmon in the BA are only possible with highly selective use of the available data and extrapolation of their results to all pink salmon in the BA. In assessing and managing pink salmon in the BA, all potential impacts on the productivity of these pink populations, including sea lice, should be acknowledged in developing an effective management strategy.

And here is Dr. Krkosek’s response.

The response by Krkosek et al is such a confusing, technical, and complicated response (much like the original paper) that it loses most readers within a paragraph, leaving only a handful of expert mathematicians that could actually understand and comment. The rest of us will be baffled by the complexity and bewildered by the fact that the response doesn’t address any part of the well-articulated criticism. It is a clear attempt to obfuscate the issues and hide behind jargon and complexity.

Considering Dr. Krkosek wrongly predicted the extinction of the Pink Salmon in the Broughton Archipelago in British Columbia and consistently comes to the same gloomy conclusion all over the world with his models and statistics what are the chances of such biased researchers ever finding a true causal relationship? Zero.

Because salmon farms are already convicted in the court of public opinion without a shred of evidence.


St Andrew’s University press release:

Large numbers of salmon are killed by parasites, finds new study

Wednesday 7 November 2012

An “unexpectedly large” number of free-ranging salmon are being killed by parasitic lice in European waters every year, according to the results of a major international study.

The study, published today (November 7) in Proceedings of the Royal Society B, involved experts at the University of St Andrews and is the first evidence of the full impact of sea lice on salmon mortality levels.

Professor Christopher Todd, of the Scottish Oceans Institute at St Andrews, was part of an international group which found sea lice to be responsible for 39 per cent of the mortalities amongst salmon in the Northeast Atlantic Ocean.

Professor Todd, a Professor of Marine Ecology, collaborated with experts from New Zealand, Canada, Ireland and Norway in the research paper.

He said: “For the first time we can effectively place a reliable value on the predicted mortality loss of free-ranging salmon subject to infection from this parasite.

“This high per cent mortality attributable to sea lice was unexpected. The salmon aquaculture industry has long placed a high priority on controlling sea lice on their captive salmon – but these results do emphasise the need for the industry to not only maintain the health of their own stocks, but also to minimise the risk of cross-infection of wild fish.”

Sea lice are natural parasites of wild salmon and also present the salmon aquaculture industry with major challenges as the parasite can debilitate or kill the salmon host. Natural mortality of wild salmon during their ocean migration can be as high as 90-95 per cent, but over the past 20 years controversy has surrounded the contribution of sea lice parasites to salmon mortality.

The research team analysed data relating to experimental releases of young salmon, and their rates of survival when they returned to freshwater a year later as mature adults.

The data analysed included 24 trials carried out between 1996-2008 which involved 280,000 smolts (young salmon) which had been individually tagged, before their release, into 10 rivers in Ireland and Norway.

In each trial half the fish were treated chemically before their release to protect them from sea lice infection during their first 1-2 months at sea. The remainder in each trial were untreated control fish. A proportion of each group were then recovered as adults on their return to coastal waters a year later.

By comparing the tags recaptured from both the treated and control groups in each trial, the researchers showed that sea lice were responsible for an average 39 per cent of the total mortality losses of salmon at sea.

Professor Martin Krkosek of the University of Otago, New Zealand, who led the study, said: “Our research is similar to clinical studies in medicine – except that wild fish are the patients.

“Usually we think of food, climate, predators and fishing as the major drivers of fish abundance, but we have learned that parasites are taking a very large share of the catch.”

The study involved the Scottish Oceans Institute at the University of St Andrews, The Department of Zoology at the University of Otago in New Zealand, the Atlantic Veterinary College at the University of Prince Edward Island in Canada, the Inland Fisheries in Ireland, the Institute of Marine Research in Norway, and the Norwegian Institute for Nature Research.