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article imageDrug-resistant sea lice out of control on B.C. Coast

By Karen Graham     Nov 4, 2018 in World
Fisheries and Oceans Canada confirms the findings of independent research that says sea lice on salmon farms are becoming resistant to SLICE, a pesticide used to kill sea lice.
An infestation of sea lice forced the closing of Cermaq Canada’s Fortune Channel salmon farm near Tofino over the summer. Cermaq Canada spokeswoman Amy Johnson didn't give the exact number of salmon that had to be euthanized but noted that the company has “several hundred thousand fish” at each of their farm sites.
“Closing the site was the right thing to do as the fish were never going to recover well and would remain a target for sea lice,” Johnson told the Westerly News via email on October 27.
Sea lice becoming resistant to SLICE
The closing of Cermaq Canada's fish farm came on the heels of a report from the Living Oceans Society and Alexandra Morton's Raincoast Research Society. Called “Lousy choices: Drug-resistant sea lice in Clayoquot Sound,” the report highlights the fact that sea lice are becoming resistant to SLICE, the only pesticide approved for sea lice control in Canadian fish farms.
“The spring of 2018 saw parasitic sea lice on both farmed and wild juvenile salmon in Clayoquot Sound reach levels never before seen in the province of B.C.,” the report states. This has “grave implications” for both the salmon farming industry and wild salmon, the report further states.
The development of drug and chemical resistance in sea lice is a problem that industry, government, and conservationists have known about for many years. SLICE, an emamectin benzoate drug, was first used on Canadian salmon farms in 1999 - but was approved on an emergency basis only. It wasn’t fully approved until 2009, but as use continued the trend toward resistance became apparent.
However, because of a visible resistance of sea lice to SLICE creating a "crisis situation" in southwest New Brunswick in 2009 and 2010 and emergency registration was granted by PMRA for Salmosan®, Paramove® 50 and AlphaMax®.
The report claims that DFO Canada has been aware of the poor results using SLICE since 2014, despite their public denials. A June 2014 email obtained through the Access to Information and Protection of Privacy Act (ATIP) from DFO senior aquaculture biologist Kerra Shaw reports: “there is some indication from Broughton Archipelago bio-assay work that sea lice tolerance to [SLICE™] emmamectin benzoate may be developing. It is recommended that Cermaq have a site-specific condition added to their license requiring laboratory bioassay work to be conducted on sea lice from this farm [Sir Edmund] to continue to learn more about treatment efficacy. This data will be used by Cermaq and DFO to appropriately manage sea lice and treatments in the future”
However, the report states this recommendation was not made a condition of licensing and tied the DFO's hands as far as tracking and responding to the sea lice threat to wild salmon.
The 2017-2018 winter
Over the winter of 2017 and spring of 2018, salinity levels that normally drop with increased rain did not occur, Dan Bate, communications lead for Fisheries and Oceans, Pacific region said in an email. “This higher salinity resulted in increased lice production in the region and exacerbated the lice levels on farms,” Bate wrote.
And of course, with fish farms being packed with farmed salmon infested with sea lice, it is only natural that wild salmon swimming near the nets will also pick up the parasites. It only takes one to three sea lice to kill a juvenile salmon.
“Eighteen years after this issue was brought to DFO’s attention there is still no protection for wild salmon,” said Alexandra Morton, one of the report’s authors with Raincoast Research and an outspoken critic of salmon farming. “I don’t hold hope that much of this generation of wild salmon survived,” she said.
Shawn Hall, a spokesman for the B.C. Salmon Farmers Association says fish farms are now using a new technology to address the sea lice problem. A barge or a boat, with a pool, called a "hydrolicer" is used to “gently move a pen of fish into a well and use pressurized seawater to wash the lice off.” The lice are then collected and disposed of on land.
"Sea lice naturally occur in the ocean and are on numerous fish species. Indeed, as smolts, our fish move from land-based hatcheries to ocean pens without sea lice and pick them up in the ocean. We manage the risk of sea lice transferring back from farms to wild salmon with what’s called an integrated pest management approach, with prevention efforts, monitoring, federal regulation, and tools including the new hydrolicers,” Hall said
More about Sea lice, British columbia, Fish farms, slice, salmon populations
 
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