According to a recent study carried out in part by the Scottish Oceans Institute, parasitic lice are killing a large number of free ranging salmon in European waters every year.
There is little experimental data on the impact of parasites on salmon population, marine fisheries and conservation. The study, which involved the release of 280,000 tagged fish into 10 rivers in Ireland and Norway, is said to be the first evidence of the full impact of lice on salmon mortality levels.
Professor Christopher Todd, Scottish Oceans Institute at St Andrews University, said: “This high percent 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."
Although producers say 95% of salmon will die naturally at sea during migration, sea lice are natural parasites of wild salmon and present the salmon aquaculture industry with significant challenges, often weakening or killing the salmon host.
The study found that sea lice are responsible for 39% of the deaths among salmon in the northeast Atlantic Ocean. The industry has been urged to protect the health of its stocks in order to minimise the threat to fish recruitment, fisheries and conservation.
