Salmon louse numbers have risen so much that the parasites could now pose a threat to wild stocks, new research has suggested.
New research published today in the Proceedings of the Royal Society by scientists from the University of Alberta has shown how sea lice on farmed fish can infect wild juvenile salmon.
The paper described the results of a study of wild juvenile Pink salmon, Oncorhynchus gorbuscha, and Chum salmon, Oncorhynchus keta, which looked at sea lice infections on the fish as they made their journey out to sea past a series of fish farms containing salmon infected with lice.
Every few miles, the juvenile salmon were sampled and the number of parasites on them was recorded. Before the fish reached the infected farms the wild salmon were uninfected, but became infested with parasites as they past by.
Martin Krkosek, one of the authors of the paper, told The Guardian: "Sea lice production from the farm we studied was four orders of magnitude, 30,000 times, higher than natural levels.
"Our research shows that the impact shows that the impact of a single farm can be far reaching."