Salmon farms should be worried about more than just one species of sea lice, researcher says

Migrating young sockeye salmon that are highly infected with parasitic sea lice grow more slowly, according to a new study from Simon Fraser University researchers.

That matters, the experts said, because growing quickly can be the difference between life and death for vulnerable juvenile salmon.

"Previous studies have shown that to survive to adulthood, young salmon need to get big fast," said Sean Godwin, a PhD student at SFU and lead author on the study.

"Those that grow more slowly as we found, those heavily infected with sea lice those fish are more likely to die."

Many people opposed to fish farms have raised concern over declining wild Fraser River sockeyeandthe potential for parasite transfer from salmon farms.

Wild salmon pass the farming stations as they migratealong the coastline, and lice from the farmscan spill into the ocean, latching on to wild sockeye as they go by.

Salmon farms do have measures to monitor and control one species of sea louse, but nearly all the lice found onthis study's juvenile salmon were a different species whichisn't targeted in currentmeasures.

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• 2011 study says Wild salmon sea lice linked to B.C. fish farms

Current sea lice treatment protocol

Twospecies of sea lice off that live off theWest Coast areC.clemensi and L.salmonis.

The B.C. Salmon Farmers' Association'streatment regime, set out by the DFO, is only set in motion when L.salmonis numbers get too high. Thattreatmentwipes out C.clemensi, too.

The problem, Godwin said, is thatC. clemensi lice can spreadunchallenged, so long as L.salmonisnumbers are low.

He said those outbreaks have "happened before."

A studypublished in Februaryfound the average number of L.salmonislouse per fish on a B.C. farmwas only 2.3 in 2013 numbers that aren't high enough to raise a red flag.

There were dozens of C. clemensi louse on each of those fish,but those figures wouldn't havetriggered treatment.

Godwin noted that it's not proven that theparasites he saw during his study came from fish farms, or that the lice were the direct cause of the slowed growth.

But because there's a chance of that,Godwinsaid officials should keep that second species in mind.

"I think there is mounting evidence that this species of sea louse that everyone's ignoring ... this species could have real impacts on our wild sockeye."

Parasites'well controlled,' association says

Jeremy Dunn, executive director with the BCSFA,said L.salmonisis the bigger concern for the association because it affects salmon more often thanC. clemensi, which mostly affects herring.

"So, that's been the lice that the DFO has developed the management action around," he said.

Hesaidall farms are required to regularly monitor sea lice levels on their farms and report them to the DFO, which posts the figures online.

Dunn saidmany farms are "actually unaffected" by C.clemensiand that, overall, parasites are "well managed and well controlled."

When asked about Godwin's study, Dunn said the association considers all kinds of data.

"I think it's an interesting study ... From a management perspective, I think the DFO and farmers are always taking new science into account," he said.

Godwin said he hopes that'll bethe case going forward.

"What I hope is that we could start considering this species of sea louse that actually infects our wild juvenile sockeye salmon when making parasite management decisions on salmon farms along the sockeye migration route."

With files from Lisa Johnson