Were David Attenborough to visit the west coast of Ireland in search of natural drama, he couldn't select two more controversial species for study than Caligus elongatus or Lepeoptheirus salmonis.
Long before fish farm cages were ever imagined on this island’s coastline, sea lice larvae were the bane of wild salmon and sea trout, attaching themselves and grazing on the mucus, skin and blood of the fish.
The same lice were regarded as a good sign for the restaurateur, indicating the freshness of a returning wild fish.
However, the role that aquaculture might play in elevating lice levels – transferred from adult wild to farmed fish and from there to juvenile wild fish leaving river mouths – came into sharp focus over two decades ago when there was a much publicised collapse of sea trout stocks in the western game fisheries.
Nine years ago, two marine scientists, Martin O'Farrell and Neil Bass, came to the conclusion that there was little or no evidence to support fish farms being the major culprit. They noted that an erratic decline in stocks of both salmon and sea trout was charted in Scotland, and much of it predated salmon farming by up to 30 years.
Human factors, such as catching sea trout as a by-catch in drift nets, installation of upstream and downstream traps by private fishery owners, and acidification caused by afforestation were more likely culprits, they said.
Still, serious differences over the issue have surfaced again in relation to Bord Iascaigh Mhara's plans for a 15,000-tonne organic salmon farm in Galway Bay. While there is no effective anti-lice vaccine, there is a national sea lice monitoring and control programme which the European Commission has expressed satisfaction with.
Yet several State bodies are at odds over the issue. A recently completed Marine Institute-led study of returns of Atlantic wild salmon to river basins says pollution and poor water quality, rather than fish farms, are the main cause of stock mortality, and suggests that the State's own scientific data indicates rivers in districts with salmon farms "have performed best in terms of meeting their conservation limits" and ability to support a commercial catch.
'Steady improvement'
The study for the peer-reviewed Agricultural Sciences journal says there is a "steady and sustained improvement in the overall status of Irish salmon stocks". The paper followed a previous nine-year study which concluded that infestation of outwardly migrating Atlantic salmon smolts by sea lice was only a "minor component of overall marine mortality" .
The study, led by David Jackson, analysed the return rates of fish treated to protect against sea lice with untreated "control" fish – reviewing data on 352,142 migrating salmon from 28 releases at eight locations along Ireland's south and west coasts from 2001 to 2009.
Data published by Inland Fisheries Ireland (IFI), the State body responsible for wild salmon, and previously unpublished data from the Burrishoole and Bundorragha (Delphi) fisheries in the west was included in the review.
A similar study conducted in Norway, published this year in the Journal of Fish Diseases, came to a similar conclusion. The study led by Ove Skilbrei involved 650,000 salmon smolts released in "paired experiments" across 16 rivers over a 10-year period.
However, Inland Fisheries Ireland begs to differ. It says the basis on which the status of salmon populations in each river has been assessed for the Marine Institute-led study is fundamentally flawed and that the categorisation techniques deployed “totally misrepresent salmon numbers in Irish rivers”.
It says the study has drawn “blanket conclusions regarding fish stock numbers in rivers currently designated as ‘Open’ which fail to recognise that fish populations would vary significantly within this category, depending on the specific river concerned”.
For example, north Mayo’s river Moy and Drumcliff river in Sligo both have an “open” categorisation, yet one has a surplus of 26,000 salmon above conservation limits (as in numbers that allow fish to spawn) while Drumcliff has a surplus of just 85.
IFI also says the “steady and sustained improvement in overall stock status referred to in the [Marine Institute] study has not been scientifically factored against the fact that more rivers have been opened to anglers since 2007 and that there have also been significantly improved levels of reporting since a new statutory regime was introduced in that year”.
It has cited “international research from Ireland and Norway”, indicating that 39 per cent of salmon mortalities are attributable to sea lice, most likely acquired during early marine migration in areas with salmon farms, and that sea lice from salmon farms can affect sea trout over a distance of up to 30km.
New Zealand-based Irish scientist Mark Costello, currently associate Professor in Marine Ecology at the University of Auckland and a former technical consultant to the Aquaculture Licence Appeals Board (ALAB) here, has recently echoed IFI's concerns and has written a letter to Minister for the Marine Simon Coveney, citing computer modelling and field data studies in Ireland, Scotland, Norway and Canada.
Prof Costello’s letter, which was circulated by the Friends of the Irish Environment, was penned initially to counteract “inaccuracies” which he says he had read in this newspaper in relation to the sea lice issue generally.
Bord Iascaigh Mhara has stressed that, if the project is approved, it will apply management standards to whichever company leases the fish farm which will "exceed existing environmental and safety regulations". The Marine Institute doesn't want to engage publicly on the issue, due to the fact that Mr Coveney is still considering applications for Galway Bay and other fish farm projects.
The undercurrent in all this is that IFI is perceived to be close to the angling community,which has no love for fish farms, while the Marine Institute is perceived to be somehow compromised by its role in sea lice monitoring and control.
The Minister may need to find an independent international expert or seek publication of an EU-funded project on the “sustainable management of interactions between aquaculture and wild salmonid fish”, known as Sumbaws, which involved Scottish, Norwegian and Irish research.
Differences over science and sea lice - the Canadian experience
Ireland is not alone when it comes to controversy over the science behind fish farms. Research in Canada, some of which has been cited by opponents of fish farms here, has been called into question by Vancouver-based Financial Post columnist and blogger Vivian Krause.
Krause, who formerly worked in the aquaculture industry, investigated the links between private funding organisations and environmental groups. In February 2008, she submitted to the University of Alberta a complaint of apparent scientific “misconduct” in sea lice research conducted under its auspices.
She claimed the research had not actually measured sea lice levels at fish farms, but relied on computer-generated models which predicted mortality ranges between nine and 95 per cent. She believed the journal where the research appeared had a conflict of interest in having editorial links to a foundation which had funded a public relations campaign against fish farming.
The University of Alberta told The Irish Times it stood behind the peer review process.
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