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Going Viral: A Major IHNV Outbreak in Puget Sound

Information about IHN outbreak in Puget Sound and BC

Recently, a major outbreak of Infectious Hematopoietic Necrosis virus (IHNV) occurred at three Atlantic salmon farms off Bainbridge Island in Puget Sound, just minutes from downtown Seattle: Fort Ward, Clam Bay, and Orchard Rock. There have also been outbreaks at three salmon farms in BC: Atlantic salmon net pens at Dixon Bay and Bawden Point, both north of Tofino, and a coho salmon facility at Ahlstrom Point, near Sechelt.

IHN Bainbridge

Even though IHNV is naturally occurring in the Pacific Northwest, viral amplification is a serious concern. Net pens can create an environment that is conducive to the production of more virulent strains of the virus. Given the high densities of the farmed fish in the pens (and a lack of resistance in Atlantic salmon to IHNV), these operations have the potential to release millions of viral particles into the seawater flushing through the pens with each tide, with the potential to infect juvenile wild salmon passing by on their outmigration to the Pacific Ocean (the virus can survive for up to three weeks in seawater). Juvenile salmon are at the highest risk of mortality from IHNV infection, although survivors may act as carriers of the virus and may also shed viral particles when stressed; in some cases adult fish succumb to the infection.

Currently no agency monitors the effects of net pen disease outbreaks on wild fish and the environment, as was the case in the Bainbridge Island outbreak. There is also no guarantee that public notice will be made, including notification to consumers of diseased fish (labeling) and the possibility that a purchased fish could still spread the disease.

The recent outbreak at the three facilities in Puget Sound is quite concerning because of the speed at which the disease spread; too many net pens are too close together. Even one net pen increases the risk to the environment but three this close together is a recipe for disaster. Let's also consider the placement of these feedlots: floating between two Washington state parks, the Orchard Rocks marine reserve (two of the net pens are actually within the reserve's boundaries), the Northwest Fisheries Science Center’s Manchester Research Station, and right smack in the middle of prime wild salmon habitat. We spend millions of dollars every year to save wild salmon yet we allow risky business practices to threaten our investment.

Shouldn't our state and federal agencies be responsible for monitoring the effects of net pens on the environments in which they are located? Should we allow permitting for something that risks the health of our delicate ecosystems? Stay tuned for more on this important coast-wide issue. Our upcoming 2012 Wild Fish Journal will take a closer look at the current state of aquaculture and answer some of these questions.

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