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Salmon parasites travel miles for new host

AUSTRALIA - Sea lice, the most harmful parasite in salmon farming, can travel up to 50km to infect a host, suggests research at The University of Auckland.

Salmon parasites travel miles for new host - AUSTRALIA - Sea lice, the most harmful parasite in salmon farming, can travel up to 50km to infect a host, suggests research at The University of Auckland.

A paper published this week in Trends in Parasitology finds that as few as five lice may result in the death of a salmonid (i.e. salmon, trout and char species). In addition, the paper concludes that sea lice on salmon disperse over distances of 20-50 km.

Sea lice skin parasites are the most harmful parasite in salmon farming, causing losses estimated at 170 to 270 million per year globally. The abundance of salmon in farms in coastal waters has increased the number of available hosts, and epidemics have occurred in farmed and wild fish in areas of Ireland, Scotland, Norway and British Columbia.

"One of the most challenging research questions has been how lice find new hosts," says Dr Mark Costello of the Universitys Leigh Marine Laboratory. "Lice from farms may be infesting wild trout and salmon at fatal levels. As the growth and reproduction of both sea lice and their hosts are strongly temperature dependant, sea temperature warming due to climate change is likely to upset natural balances, with consequences for fisheries, farms and coastal ecosystems. Patterns of infestation on wild hosts suggest that lice may already be more harmful than previously appreciated."

"Analysis suggests that few sea lice are needed to infect a host and each louse can travel up to 50km in open water. Research has enabled better farm management practices to control sea lice, including avoidance of infestations, use of parasiticides, and biological control using local cleaner-fish. Further research may provide opportunities to breed more lice resistant salmon and aid the natural host defences against sea lice."

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