Sea lice from farmed salmon infesting wild salmon in British Columbia
The authors of a report recently published in The Canadian Journal of Fisheries and Aquatic Sciences conclude that salmon farms are the main source of the sea lice that have been discovered on wild salmon throughout the coast of British Columbia.
The research work draws attention to the fact that these lice now appear to be affecting a greater area of wild salmon than first thought.
Some scientists believe that the wild salmon become infested with the sea lice when they migrate past fish farms. The sea lice are known to attach themselves onto the outside of the fish which leads to infections, stress and finally death.
On the Broughton Archipelago in Canada, which is a key route for migrating wild salmon, a connection has previously been established between the sea lice plaguing young wild salmon and the salmon farms with open net-pens.
This recent study has highlighted that the Georgia Strait and other areas with a high number of fish farms showed the highest infection rates of lice on wild fish.
For example, the Discovery Islands, which is a region that has one of the highest concentrations of salmon farms, was found to have the worst infestation of sea lice in wild salmon. To contrast this, the research demonstrates that areas without fish farms have lower rates of wild salmon being contaminated with the sea lice.
In other countries such as Norway and Scotland, links have been made between the collapse of important wild salmon populations and sea lice infestations. Salmon is intensively farmed in many parts of British Columbia and is an important industry.
Professor John Reynolds from Simon Fraser University, an author of the report, notes that "our research underscores the value of moving open net pen salmon farms out of migration routes of wild salmon, and ultimately into land-based closed containment systems".
The research into the outbreaks of sea lice and the impacts on wild salmon populations has highlighted the importance of using fish farming management techniques that also incorporate assessing impacts on migrating wild fish.
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