Salmon Aquaculture (smolt)

Impacts & Issues: Sea Lice & Disease

Juvenile pink salmon infected with sea lice. Photo by Alexandra Morton.High concentrations of fish in open netcages provide the perfect conditions for breeding disease and parasites such as sea lice among farmed fish. Their unnatural densities and high stress levels make farmed salmon highly susceptible to naturally occurring salmon diseases like infectious hematopoietic necrosis (IHN) and bacterial kidney disease (BKD). The proliferation of sea lice on salmon farms creates a lethal problem for wild salmon. These parasites latch onto the fish and in the right conditions multiply far beyond normal levels.

Because netcage salmon farms are open to the ocean, these diseases can be passed back and forth between wild and farmed salmon.

In 2011, Infectious Salmon Anemia Virus (ISA)v, was found in salmon in several areas of coastal BC. As this is an exotic disease, it can only have been introduced to BC waters. The most likely source is in eggs imported for the open net cage farms. Although the open net cage industry and governments have denied the presence of ISA, testimony at the Cohen Inquiry has indicated that DFO has been aware of problem for years.

While sea lice occur naturally in BC coastal waters on adult salmon, they thrive in the factory-farm conditions of salmon farms, with up to a million fish on one site. Repeated infestations are transforming the farms into year-round sea lice reservoirs.

The presence of sea lice on farms leads to the infection of fragile juvenile wild salmon as they emerge from their natal streams and migrate past the fish farms.

Peer reviewed, published research indicates infestations as low as 1 to 3 lice can be fatal to juvenile pink and chum salmon (Morton/Routledge, Alaska Fisheries Research Bulletin, Winter 2005).

Estimates of the total salmon mortality caused by sea lice originating on farms to be up to 95% of wild juvenile pink and chum salmon (Krkosek, Lewis, Morton, Frazer, Volpe, PNAS, 2006).

    If you meet anyone who still imagines that sea-cage farming does not harm wild fish, please direct them to read the paper published in the Proceedings of the National Academy of Sciences. One does not have to be a scientist to read it. The senior authors paid extra to have the paper accessible by the public. Criticism of the paper and the responses of the senior author can also be found online.“ Dr. Neil Frazer

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