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Sea Lice Infections Increase Mortality In Wild Salmon

by the Fish Site Editor
31 August 2011, at 1:00am

CANADA - A study has found sea lice infections at fish farms in British Columbia could be linked to increased mortality among wild salmon, which contradicts a previous study.

The Atlantic Salmon Federation said those incidents of infections are something Newfoundland fish farms should be watching for, as the aquaculture industry grows in this province.

Don Ivany, the federation’s regional director, said the aquaculture industry does some monitoring of its own fish, but wild salmon that could be swimming past fish farming facilities aren’t necessarily monitored.

“We’re not quite sure of any level of monitoring that has occurred. It’s one of those grey areas we really aren’t sure of,” said Mr Ivany.

“Inspections are supposed to be taking place within the aquaculture industry but often aren’t, and when they aren’t, violations often aren’t detected and action is not taking place.”

Sea lice attach themselves to salmon or any fish to feed on blood. In the wild salmon population, juveniles are particularly vulnerable, Mr Ivany said, and when a young fish gets seven or eight sea lice attached to its body, as has been found on the west coast, that fish could die.

It’s not unusual for anglers to pull a wild salmon from a river with a couple of lice attached to it.

When the salmon move from the salt water of the ocean to the fresh water of a river it usually kills the lice, as lice cannot adapt to fresh water.

“If (an angler catches) a salmon with sea lice on it that means it just came in from the ocean,” said Mr Ivany.

“I won’t say they’re common but they’re not uncommon either, but they tend to fall off after a few days in fresh water.”

Miranda Pryor, executive director of the Newfoundland Aquaculture Industry Association, said her group is just as concerned with sea ice, but Newfoundland and Labrador’s colder water temperatures means sea lice is not as much of a problem as on the Pacific coast.

“That’s one of the natural ways of helping to avoid the problem,” she said.

“Salmon runs are primarily in the spring and because sea lice are very temperature dependent we don’t see them until later in the summer when the water temperature is at its peak.”

She said owners of fish-farming facilities have several rules to follow. The farms are regularly monitored and health reports have to be routinely submitted to fish health authorities. Any treatments, she said, are also monitored.

the Fish Site Editor

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