Salmon inquiry
Contrary to recent perceptions, the industry in Scotland is making real headway
THE assertion by a leading academic that sea lice are mostly under control in Scotland has been challenged by a solicitor representing the angling lobby in Scotland.
Professor James Bron, from Stirling University’s Institute of Aquaculture, gave evidence last month to the Sco sh parliament’s Rural Economy and Connectivity (REC) committee, which is conducting an inquiry into salmon farming (see reports, next page).
The committee has also heard from the wild salmon sector and will be gathering further evidence in April and May, from government bodies, regulators and, eventually, from the salmon industry itself.
On May 2, Ben Hadfield, Craig Anderson and Grant Cummings, the bosses (respectively) of Marine Harvest Scotland, the Sco sh Salmon Company and Grieg Seafood will answer MSPs’ questions.
The salmon sector remains under attack from certain elements within the angling community, whose grievances are not necessarily science based, as the following exchange demonstrates.
Guy Linley-Adams, solicitor for Salmon and Trout Conservation Scotland (S TCS), in a written submission to the REC committee, took Professor Bron to task over his sea lice claims.
Linley-Adams quoted last month’s report from the Environment, Climate Change and Land Reform (ECCLR) committee, saying The committee believes the efforts of the industry have proven to be largely insu cient to address lice issues.’
He also quoted a report by SAMS (the Scottish Association for Marine Science) stating that the main treatment methods used in Scotland are experiencing reduced e cacy in dealing with sea lice on farms’.
And he referred to responses to his group’s Freedom of Information requests to the Fish Health Inspectorate which showed, he said, that the current sea lice figures on fish farms in Scotland are not encouraging’.
Below is Professor Bron’s response
Mr Linley-Adams referred to the following statement, which I made during the evidence session mostly sea lice are under control in Scotland and, as I said, if you look at the data that has been produced there has been no rise in sea lice. So I think there is an impression that there has been a sort of skyrocketing of sea louse numbers but actually, if you look at the average, that’s remained relatively static there ’
The above comment referred back to a statement that I had provided earlier in the same session, in which I indicated that if you look at the actual figures, and there is a recent paper by Hall and Murray, we can see that actually the numbers of sea lice have not been increasing, and the reason they are not increasing is that we have a lot more tools at our disposal to help us control these pathogens.....’
Mr Linley-Adams questions this in his communication to the committee, saying that as farm-specific sea lice data is not publicly available, it is not clear what the basis can be for Professor Bron’s statement’, and asserting that what published data there is does not support Professor Bron’s evidence that mostly sea lice are under control in Scotland’.’
Mr Linley-Adams is incorrect. The statements to the committee which Mr Linley-Adams contests are based on the reported findings of a recent study.
This publication is in the public domain and employs data that are also in the public domain, and indeed are used by Mr Linley-Adams in his communication.
My statements to the committee were informed by Hall L.M. and Murray A.G. (2018)- describing temporal change in adult female Lepeophtheirus salmonis abundance on Sco sh farmed Atlantic salmon at the national and regional levels. Aquaculture, olume 489, Pages 148-153 (http //www.sciencedirect.com/ science/article/pii/ S0044848617318367).
The authors of this paper work at Marine Scotland Science (MSS) which is the scientific division of Marine Scotland, a directorate of the Sco sh government responsible for the integrated management of Scotland’s seas.
The authors of the paper are internationally regarded leading statisticians/modellers in their field, and the paper is published in a respected peer reviewed scientific journal. Having analysed data available at
Left: James Bron. Below from left: Ben Hadfield, Craig Anderson and Grant Cummings. Opposite page: Guy Linley-Adams
national and regional levels, the authors of this paper concluded in the abstract to their paper that, with regard to sea lice abundance between December 2010 and September 2017
longer term changes at the national level and for two regions were also detected with no apparent overall increase occurring over the period.’
Which is what I stated to the committee in evidence.
I would now like to draw the committee’s attention to other aspects of the analysis presented in this paper, something I did not do in the evidence session due to time constraints.
There is an apparent decline in sea lice abundance at the Sco sh national level, running from mid-2015 to the last data point in September 2017.
I contend that this demonstrates improvement in sea lice control, despite complicating factors such as complex gill disease, and I would argue that this has been achieved through increasingly successful use of a range of non-medicinal management tools, for example, cleaner fish and physical removal methods in addition to use of veterinary medicines.
Regional level models are presented in Hall and Murray’s paper. It can be seen that in the Northern Isles, Western Isles and North Mainland reporting regions there is a trend for relatively little change or even a decline in sea louse abundance.
In the South Mainland region there is a slight upward trend in abundance, though it should be noted that there are quite wide confidence bands around the data at this end, suggesting higher variability and a less predictable line (i.e. the actual abundance might be higher or lower than that described by the model fit).
On the basis of the analysis presented by Hall and Murray (2018) I consider it correct to suggest, as stated in my evidence to the committee, that from a national perspective sea lice are mostly’ under control.
As discussed in the committee meeting, this control is exerted by the use and gradual improvement of integrated pest management strategies (IPMS) that employ a broad range of tools. The use of multi-component IPMS mean that sea lice control in Sco sh fish farming is increasingly less dependent upon, though still requiring, the use of veterinary medicines.
This is not to say that the mean numbers of lice per fish cannot be improved in the future, or that every farm has been able to keep numbers to a satisfactory level, but overall I consider that the industry in Scotland is making real headway in control of lice.
I do not dispute Mr Linley-Adams’ suggestion that sea lice numbers on some sites exceed nominal trigger thresholds’. As I indicated in evidence, however, nowhere have these thresholds been scientifically established and, where set very low, farm louse estimates cannot easily be statistically validated.
However, rather than automatically triggering specific treatments, these are in practice decision thresholds’ that prompt farm staff, health teams, responsible vets and others to make decisions about best management, taking into account specific contextual factors (for example, fish health and welfare state, site parameters, stage of production cycle, presence of other diseases, algal blooms, water temperature, weather considerations, and so on).
Treatment decisions should not be based simply on estimated numbers of adult female lice derived from a small sub-sample of fish.
Mr Linley-Adams included the following quote from the SAMS report in support of his contention that sea lice are not under control in Scotland The main treatment methods used in Scotland are experiencing reduced e cacy in dealing with sea lice on farms. New techniques are being applied, although the long-term success of these is uncertain. The legislative and voluntary frameworks that underpin the management of lice levels on farms are not transparent. They appear neither to be succeeding in controlling sea lice, nor capable of addressing the environmental effects of the lice.’
To be clear, in my opinion, and based on my scientific knowledge and expertise in this area
1. While some veterinary medicines show reduced e cacy in some regions/farms, the widespread use of IPMS means that they are rarely the only or main treatment method employed on Sco sh fish farms.
2. The wide range of new non-medicinal techniques being applied, including cleaner fish, functional feeds, barrier methods and physical removal techniques, are currently proving successful at reducing louse numbers.
3. Whilst the contribution of individual components in IPMS is less clear, the currently employed range of tools and techniques for the management of sea lice is mostly’ controlling sea lice numbers on Sco sh fish farms.
4. Whilst it is not feasible that there is no environmental impact of sea lice, well supported evidence for the existence of any significant environmental impact of lice in Scotland is largely lacking. In my view, the ability of existing frameworks to address any environmental impacts of sea lice cannot easily be assessed until that evidence is available.
The full submissions can be read at http //www.parliament.scot/ S5 Rural/Meeting 20Papers/20180314 REC Committee - Updated Public Papers.pdf
“The numbers of sea lice have not been increasing we have a lot more tools at our disposal to help us control these pathogens”