An “unexpectedly large” number of free-ranging salmon are being killed by parasitic lice in European waters every year, according to the results of a major international study. The study, published in Proceedings of the Royal Society B, involved experts at the University of St Andrews and is the first evidence of the full impact of sea lice on salmon mortality levels.
Professor Christopher Todd, of the Scottish Oceans Institute at St Andrews, was part of an international group which found sea lice to be responsible for 39% of the mortalities amongst salmon in the Northeast Atlantic Ocean. He collaborated with experts from New Zealand, Canada, Ireland and Norway in the research paper. Todd said that for the first time a reliable value on the predicted mortality loss of free-ranging salmon subject to infection from this parasite could be effectively placed.
Sea lice are natural parasites of wild salmon and also present the salmon aquaculture industry with major challenges as the parasite can debilitate or kill the salmon host. The researchers showed that sea lice were responsible for an average 39% of the total mortality losses of salmon at sea.
Professor Martin Krkosek of the University of Otago, New Zealand, who led the study, said that usually food, climate, predators and fishing were thought of as the major drivers of fish abundance, but now it can be seen that parasites were taking a very large share of the catch.
The study involved 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, the Inland Fisheries in Ireland, the Institute of Marine Research in Norway, and the Norwegian Institute for Nature Research.
Source: University of St Andrews