Industry delight as study shows lice not to blame for salmon deaths

A Marine Institute study which says sea lice do not play a significant role in salmon mortality has been welcomed by the seafood industry.

The impact of sea lice generated by fish farms is a huge source of controversy internationally with environmentalists and anglers arguing that farmed fish pens create high levels of sea lice which pose a potentially fatal threat to young wild salmon returning to sea.

The study, carried out by the Marine Institute based in NUI Galway, found that sea lice infestation was unlikely to be a significant factor influencing the conservation status of salmon stocks.

BIM chief executive Jason Whooley welcomed the findings of the study. He said it was confirmation of the validity of the approach BIM had taken with regard to the development of the salmon farming industry.

“The scare stories in relation to sea lice being a threat to wild salmon, put out by the opponents of salmon farming, have no basis in scientific fact,” he said.

“Ireland is uniquely blessed in having an environment naturally suited to salmon farming and all stakeholders should now unite to realise the opportunities this represents and to deliver the much needed economic and employment benefits to coastal communities.”

The research was carried out over nine years and involved more than 350,000 fish released into eight rivers in 28 experiments. Its aim was to investigate the impact of sea lice on the marine mortality of Irish salmon smolts and assess the extent of sea lice-induced mortality in wild salmon stocks.

The institute said the long-term study was “highly accurate and very reliable” and also found “the level of marine mortality attributable to sea lice infestation to be very small; about 1% in absolute terms. “At these levels it is unlikely to influence the conservation status of stocks and is not a significant driver of marine mortality,” the study concluded.

Researchers claimed the reason for other studies reaching different conclusions on the danger of sea lice was due to “flaws” in the studies.

The research acknowledged there had been an increasing trend in marine mortality, up to 2008, but there was no evidence to suggest that this trend is influenced by sea lice infestation levels of outwardly migrating smolts.