A study released on Tuesday indicates that salmon farms along British Columbia’s Broughton Archipelago are significantly amplifying sea lice in coastal waters and underscores the challenges facing industry, regulators and salmon conservationists.
The study, “Dynamics of outbreak and control of salmon lice on two salmon farms in the Broughton Archipelago, British Columbia,” was published in the online journal Aquaculture Environment Interactions. It modeled the growth of lice on two area farms located on the migration path of wild juvenile salmon, and confirmed that lice outbreaks on farmed salmon are primarily driven by louse reproduction and population growth in the farms.
“The study provides new information on the dynamics of lice outbreaks on farms that help us better understand the challenges we face in controlling lice in areas where wild salmon may be at risk,” contended lead author Dr. Martin Krkosek, professor at the University of Otago in New Zealand.
The findings contradict the results of another study released last week by the University of California Davis School of Veterinary Medicine. That study, published in the online journal Proceedings of the National Academy of Sciences, found that sea lice were not responsible for the 2002 crash of the Broughton Archipelago wild pink salmon population in western Canada. It did not, however, identify what caused the crash.
Krkosek’s study examined the use of the pesticide, emamectin benzoate, commonly known as SLICE, to control lice.
“While using pesticides to control lice may buy beleaguered wild salmon precious time, the continued use of chemical controls is not sustainable. Louse pesticides may have unintended consequences for non-target organisms in marine waters, and lice around the world quickly evolve resistance to their effects,” said Dr. Craig Orr of Watershed Watch Salmon Society, one of the study’s authors.
The challenges of controlling lice outbreaks on farmed and wild salmon have led the Coastal Alliance for Aquaculture Reform, Watershed Watch Society and other environmental groups to call on the industry to transition into land-based re-circulating (closed containment) aquaculture technology.
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