Fraser River sockeye salmon. (Photo: Fisheries and Oceans Canada)
Virus may have led to sockeye salmon's steep decline
Friday, August 26, 2011, 00:30 (GMT + 9)
Four major aquaculture companies have given up their fight and agreed to give salmon samples to federal biologists studying a newly detected virus that possibly caused the precipitous drop of wild sockeye. Dr Kristi Miller, a genetics researcher with the Department of Fisheries and Oceans (DFO), testified at the Cohen Commission this week that a virus "could be the smoking gun" that explains the deaths of millions of sockeye in recent years.
Miller wants to compare virus levels in wild sockeye against samples of farmed Atlantic salmon at different points in their lives, before and after they swim past the farms off Vancouver Island. She found wild sockeye salmon with a unique genetic signature are 13.5 times less likely to return to reach their spawning grounds than their counterparts without the signature.
The cause may be parvovirus.
“If we demonstrate that when fish are entering the ocean and they become stressed in the ocean [due to the environment], and they carry a high load of this virus, and that we see significantly enhanced mortality, there certainly is the potential that this virus could have a major impact on salmon declines,” Miller explained, Vancouver Sun reports.
DFO researcher Dr Kyle Garver, however, said it is "pure speculation" to make such an assumption.
Conclusive test results may not be ready in time for the Cohen inquiry to consider them, Tri-City News reports.
Under cross-examination by a lawyer for the salmon farming industry, Miller testified that her data showed the highest level of the mortality marker in young smolts which had not approached fish farms.
"The main time period of transmission appears to be in fresh water," she stated.
At the same time, Miller said, the virus could have originated at fish farms and farmed fish – or other species in fresh water –could be transmitting the virus back and forth with wild salmon.
Sockeye from other places also contained the lethal signature, including salmon from Haida Gwaii and the west side of Vancouver Island – fish that never migrate past fish farms.
Her group has not yet deeply studied northern stocks that return to the Skeena or Nass rivers.
Miller highlighted the lethal markers did not appear in Harrison Lake sockeye, which spend less time in fresh water and migrate around the west coast of Vancouver Island, not past the fish farms in Johnstone Strait.
"The fish that spend less time in fresh water tend to be doing better than the fish that spend more," she stressed.
There were rumours that Miller was silenced by federal officials after the publication of her latest paper in Science. She testified she had been told not to publicly discuss her findings ahead of her testimony, but that she has always been allowed to publish her results.
"I've never been told not to share research," Miller remarked.
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By Natalia Real