Non-Native Lethal Virus Found In Wild Pacific Salmon

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Posted by on October 28, 2011 at 17:01:05:

Infectious Salmon Anemia (ISA) has been found in wild Pacific Northwest salmon for the first time in a recent study. While the virus does not affect humans, it is lethal to salmon life. This is the first confirmed instance of this particular infection in the Pacific Northwest. This disease is of major concern as it is highly contagious. In Chile and Scotland, the virus has spread rapidly through aquacultured fish operations. The Centers for Disease Control and Prevention explain that the virus has spread to such an extent due to high density open ocean net pens used in most of the world’s salmon farms. In a world without these kinds of close quartered farms, the virus dies out with the sick fish. Today, in a cramped pen of salmon, a sick fish dies slowly and sheds the virus particles among the healthy population, which can then spread to nearby migrating wild stocks.

Farm stocks in other locales have been hit hard by the virus in the past. When an outbreak hits a salmon farm, more than 70 percent of the stock is typically lost.

This particular study was conducted in British Columbia due to concerns in the observable decline specifically of young sockeye salmon in the Fraser River. The results of the study were announced in Vancouver on 17 October. Of 48 juvenile sockeyes collected at Rivers Inlet along the central coast of British Columbia, "60 miles from the nearest salmon farm," 2 were found to be infected with the virus. Some scientists on the study team believe that the virus was spread via the massive import of fish eggs from Scandinavia and Iceland for salmon aquaculture, which is the way that Chile's stocks were infected in 2007. The most convincing evidence for this belief is that the two infected fish from the study tested positive for the European strain of the virus.

After making these discoveries, the researchers called for more expansive tests to examine what regions the virus is located in and which fish it is afflicting. Herring are likewise afflicted by the virus, as explained by Alexandra Morton, one of the researchers who collected the study samples, and who is also a vocal critic of British Columbia’s salmon farming operations.

The effects of the virus raise concerns not only for salmon but also for the many Pacific Northwest ecosystems that depends on them. A widespread loss of wild salmon populations in the Northwest would mean struggle for the grizzly bears, killer whales, and wolves, all species that depend on salmon as a food source. Additionally, species that salmon prey on would likely grow to excess without a predator to keep them in check, which would throw the whole ecosystem out of whack. In turn, decimation of the species would mean major problems for the businesses and communities that rely on them.

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