Plagues,
Pestilences and Diseases
Canada: Mysterious infection is killing B.C. salmon
MARK HUME, VANCOUVER— From Friday's Globe and Mail
Published Thursday, Jan. 13, 2011 6:55PM EST
Last updated Friday, Jan. 14, 2011 7:58AM EST
Large numbers of sockeye salmon are dying in the Fraser River,
before spawning, because of a mysterious virus, new research
suggests.
Historical records show that some fish always die en route to
their spawning beds, but since the early 1990s the problem has
become increasingly acute – with more than two million fish dying
in some years. Researchers have long puzzled over what was causing
the seemingly healthy fish to suddenly stop swimming and turn
belly up.
A large team of researchers from the federal Department of
Fisheries and Oceans and three Canadian universities has now found
most of the fish that die before spawning have a common “genomic
signature” – or a pattern that shows changes have taken place in
an array of genes activated to fight 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,” says the
report published in the journal Science on Thursday.
Studies on the spawning grounds show more than 70 per cent of the
salmon that died before spawning had the genomic signature.
Professor Tony Farrell, research chair at the University of
British Columbia’s department of zoology, said the research points
towards an unknown virus, but the specific cause hasn’t been
confirmed yet.
“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.”
Prof. Scott Hinch, of the department of forest sciences at UBC,
said work is already under way to try to determine where in their
life stage the fish get the infection.
He said samples of juvenile fish are being examined, to see if
they might have the “mortality-related signature” early in life,
before leaving freshwater, and samples have also been collected
from salmon at sea, during the mid-phase of life.
The research was done by 15 scientists from UBC, Simon Fraser
University and Carleton University. It was led by Kristina Miller,
head of DFO’s molecular genetics section.
Carla Shore, a spokeswoman for the federal Commission of Inquiry
Into the Decline of Sockeye Salmon in the Fraser River, said the
study is of interest but a decision has not yet been made as to
whether to call the researchers to testify.