Sea lice infestations from commercially-farmed salmon threaten wild stocks

Experts believe that the wild fish are contaminated by lice from the salmon farms, where the fish are treated with antibiotics to avoid the lice. Salmon farmers dispute the finding, saying that there is no evidence their farms are causing problems for wild salmon.

• Salmon farming has proliferated in response to consumer demand for relatively inexpensive, always-available supplies of the popular dinner entree.
• But a new study suggests that populations of wild salmon could be paying the price.
• Researchers in Canada have found that wild baby salmon - called smolts - that pass commercial salmon farms on their way to the ocean are being infected with sea lice at rates 73 times higher than normal.
• Sea lice are parasites that feed off the skin, blood and flesh of salmon.
• In salmon farms, where pens can hold tens of thousands of fish, antibiotics combat the pests.
• Sea lice on the smolts, which are about the size of a triple-A battery, can kill the fish at that vulnerable stage in their development.
• That means that increased infestation rates pose a threat to already declining wild salmon, says lead author Martin Krko{scaron}ek of the University of Alberta.
• The study was published in Wednesday's Proceedings of the Royal Society in London.
• Chile, Scotland, Norway and Canada practice salmon aquaculture on a large scale.
• Krko{scaron}ek says "there's a scientific paper trail" indicating that worldwide, such farms are associated with increased sea lice infections and declines in adjacent wild populations.
• "I haven't seen any evidence that high instances of sea lice around our farms are causing problems in terms of wild salmon," says David Rideout, executive director of the Canadian Aquaculture Industry Alliance in Ottawa.
• "The science has not shown that that's the case."
• Says John Volpe, a co-author of the study from the University of Victoria: "The take-home message here is that when the consumer expects salmon to be available year-round for $2.50 a pound, you run into trouble."