The wild salmon returning to Irish rivers to spawn are being infested with sea lice, an official report has found.
Some of the fish farms may have to close due to the high mortality rate, according to the international two-year investigation involving the State’s Inland Fisheries Ireland authority and top scientists from Ireland and abroad.
On average, 39pc of deaths among wild salmon are attributable to sea lice in areas with salmon farming, the report concludes.
The mortality results may cause the closure of some fisheries when wild salmon numbers are below conservation levels, the report warns.
And there could be serious implications for small populations of wild salmon in small rivers, it adds.
The salmon aquaculture industry is obliged to keep sea lice levels below that needed to protect wild salmon from being infested and dying.
Independent.ie Treacy Hogan Environment Correspondent
Friday November 16 2012
Sea Lice Pose Significant Threat to Wild Salmon Says New Research
About 39% of salmon mortalities were attributable to the impact of sea lice on wild salmon fisheries, according to a new international study.
The research, published in Proceedings of the Royal Society B, involved experts from Inland Fisheries Ireland collaborating with 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 and the Institute of Marine Research in Norway.
In a statement on the report, IFI says: “In previously published studies, groups of salmon smolts were treated to protect them against sea lice infestation and other groups were untreated and both groups released to sea into 10 areas of Ireland and Norway. A proportion of these released fish were recaptured as adult salmon one or more years later.
“Analysis of the results of all previously published studies together provide experimental evidence from a large marine ecosystem that sea lice can have large impacts on salmon recruitment, fisheries, and conservation. The sea lice were likely acquired during early marine migration in areas with salmon farming, which elevate local abundances of sea lice.”
IFI says the results “indicate that parasite-associated mortality may cause the closure of some fisheries when conservation targets of return adult abundances are not being met. However, the implications of these results may be most serious for small populations in small river systems.”
The inland fisheries body explains that the high natural mortality rate of both treated and untreated salmon groups was accounted for, which revealed “a large effect of parasites”.
“Precisely because natural mortality rates are high, even a proportionally small additive mortality from parasites can amount to a large loss in adult salmon recruitment,” it adds.
Minister of State for Natural Resources Fergus O’Dowd welcomed the report, stating: “From the results of this detailed study, it is crucial that sea lice levels are maintained below [designated] protocol levels, particularly in spring when wild salmon smolts are migrating to sea to avoid increased marine mortality.
Minister O’Dowd added that the results of this study “augment our knowledge in the context of proposals for aquaculture development”.
The news comes in the wake of IFI’s dispute with Bord Iascaigh Mhara over the exclusion of a report critical of the proposed new deep sea wild salmon farm in Galway Bay from the statutory consultation.
The scheme has faced opposition from local salmon anglers who fear the new facility would pose a threat to wild salmon stocks in Irish rivers by increasing the risk of sea lice infection.
Thursday, 15 November 2012
Sea lice causes 39 per cent of wild salmon deaths
The impact of sea lice in the Northeast Atlantic Ocean will affect already declining salmon stocks across Europe.
AROUND 39 PER CENT of all wild salmon deaths are caused by sea lice which is impacting wild salmon numbers and wild salmon fisheries.
A new report published by Inland Fisheries Ireland shows that the parasites could cause the closure of some fisheries if conservation targets are not met.
Publishers of the results say small populations of salmon in rivers will be most affected by the lice with the loss of genetic variability. The impact of the sea lice in the Northeast Atlantic Ocean will also affect already declining salmon stocks across Europe.
To reduce the amount of salmon stocks affected by lice, the salmon aquaculture industry in Ireland is required to maintain sea lice levels below designated levels to protect wild fish from infestation, a treatment that is having a significant positive effect on survival.
The Minister of State with responsibility for Natural Resources Fergus O Dowd said the fishing sector in Ireland is worth “an estimated €150 million annually”, so it’s important that sea lice levels are maintained below these protocol levels.
TheJournal.ie 16 November 2012