Virus could be killing sockeye salmon in Fraser River

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Friday, January 14, 2011, 23:00 (GMT + 9)

A viral outbreak might be causing copious amounts of sockeye salmon in the Fraser River to die before they spawn, according to new research published in the Science journal this week.

Although historical documentation shows that some fish always die before spawning, more than 2 million fish have been dying in some years since the early 1990's, when the problem began to strongly intensify. But the fish appeared healthy, so researchers are stumped regarding the cause.

The federal Department of Fisheries and Oceans (DFO) and three Canadian universities assembled a team of several researchers, which has determined that most of the fish that die before reaching their spawning beds hold a common “genomic signature.” The pattern reveals that changes have occurred in various genes activated to combat infection.

“Our hypothesis is that the genomic signal associated with elevated mortality is in response to a virus infecting fish before river entry and that persists to the spawning areas,” reads the report, reports The Globe and Mail.

Over 70 per cent of the salmon that died prior to spawning possessed the genomic pattern, according to studies.

The hypothesis is that the culprit is an unknown virus, even though the specific cause has not been confirmed, said Tony Farrell, professor and research chair at the University of British Columbia’s (UBC) department of zoology.

“It may not be a virus…but the hypothesis is that it is,” he said. “We need to find out if it is a virus - and if it is picked up somewhere, we need to find out where…there’s still a mystery out there.”

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Professor Scott Hinch of the department of forest sciences at UBC said research is being undertaken to discover at which point in their life stage the salmon acquire the lethal infection. Samples of juvenile sockeye are being analysed to determine whether they might have the “mortality-related signature” when young before they leave freshwater, as well as samples from salmon at sea at their mid- life stage.

Fifteen scientists from UBC, Simon Fraser University and Carleton University conducted the research, which was headed by head of DFO’s molecular genetics section Kristina Miller.

Brian Riddell, a former leading federal fisheries scientist and current CEO and president of the Pacific Salmon Foundation, a non-profit group making efforts to revive salmon populations, believes the sockeye might be infected with a virus associated with leukemia and lymphoma - which constitutes a "big red flag," reports Vancouver Sun.

Spokesperson for the federal Commission of Inquiry Into the Decline of Sockeye Salmon in the Fraser River Carla Shore noted that the study is of interest, but it has not been decided at this time if the researchers will be summoned to testify.

Related article:

- Cohen Commission contracting experts to look into sockeye fishery

By Natalia Real
editorial@fis.com
www.fis.com