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Scientists suspect virus may be cause of salmon deaths

A report published on January 14 suggests that an unidentified virus may be responsible for high mortality levels among Fraser River sockeye salmon.

The authors of the report, in the journal Science, say they found a “common genomic profile” in salmon that made them more likely to die while migrating or while attempting to spawn. The abstract of the report said:

Long-term population viability of Fraser River sockeye salmon (Oncorhynchus nerka) is threatened by unusually high levels of mortality as they swim to their spawning areas before they spawn. Functional genomic studies on biopsied gill tissue from tagged wild adults that were tracked through ocean and river environments revealed physiological profiles predictive of successful migration and spawning.

We identified a common genomic profile that was correlated with survival in each study. In ocean-tagged fish, a mortality-related genomic signature was associated with a 13.5-fold greater chance of dying en route. In river-tagged fish, the same genomic signature was associated with a 50% increase in mortality before reaching the spawning grounds in one of three stocks tested. At the spawning grounds, the same signature was associated with 3.7-fold greater odds of dying without spawning.

Functional analysis raises the possibility that the mortality-related signature reflects a viral infection.

On her blog, biologist Alexandra Morton commented on the report:

... “it is evident from this paper that DFO has known about this potential virus since 2006, but after four years they are still not certain what it is. The evolution of new viral strains is often associated with abnormal concentrations of animals or birds, like avian flu. We need to know if this is indeed a virus, if it is related to the farm salmon disease, salmon leukemia and if there is something we can do about it.”

...“We hope that Commissioner Cohen will now look into what else DFO knows about this situation and the possibility that DFO has been protecting the salmon farming industry, at the expense of the $1 billion Fraser sockeye fishery.

“I will also raise questions at the Cohen Commission whether DFO has fully supported Dr. Miller in her pursuit of this critical work and whether Miller has been given full access to the farm salmon populations for testing?”

The B.C. Salmon Farmers Association does not yet appear to have commented on the report.

Meanwhile, the Cohen Commission inquiry into the collapse of the 2009 sockeye run will resume on Monday, January 17, with two DFO officials as the first witnesses.

Crawford Kilian is a contributing editor of The Tyee.

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