A new study published yesterday in the Public Library of Science ONE by researchers from Raincoast Conservation Foundation, Watershed Watch Salmon Society, and the Universities of Victoria and Simon Fraser shows a link between salmon farms and sea lice on juvenile Fraser River sockeye salmon.
The article, Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada's West Coast, genetically identified 30 distinct stocks of Fraser sockeye that pass by open net-pen salmon farms in the Strait of Georgia, including the endangered Cultus Lake stock. The study found that parasitism of Fraser sockeye increased significantly after the juvenile fish passed by fish farms. These same species of lice were found in substantial numbers on the salmon farms.
"The implications of these infections are not fully clear, but in addition to any direct physical and behavioural impacts on juvenile sockeye, sea lice may also serve as vectors of disease or indicators of other farm-origin pathogens" said Michael Price, lead author.
The data further showed that the differences in infection level for one species of louse in relation to fish farm exposure could not be explained by differences in salinity or temperature.
"Given the high intensities of lice observed on some juveniles in this study-up to 28 lice/fish- there's an urgent need to understand the extent of threat posed by sea lice to juvenile Fraser River sockeye" said Dr. Craig Orr, a co-author of the study.
The study also recorded the highest lice levels on juvenile sockeye near a farmed salmon processing plant in the Georgia Strait, heightening concern for the full potential impact of the salmon farm industry on wild salmon in this region.
To view the study, visit:
http://dx.plos.org/10.1371/journal.pone.0016851