Disease killing Pacific herring threatens salmon, scientist warns
'I've been seeing herring with bleeding fins,' says biologist Alexandra Morton
Independent fisheries scientist Alexandra Morton is raising concerns about a disease she says is spreading through Pacific herring causing fish to hemorrhage.
Ms. Morton has called on the federal Department of Fisheries and Oceans to investigate, saying it could cause large-scale herring kills and infect wild salmon, which feed heavily on herring.
"I've been seeing herring with bleeding fins," Ms. Morton said Monday. "Two days ago I did a beach seine on Malcolm Island [near Port McNeill on northern Vancouver Island] and I got approximately 100 of these little herring and they were not only bleeding from their fins, but their bellies, their chins, their eyeballs. These are very, very strong disease symptoms."
Ms. Morton, a researcher and environmental advocate who campaigns against fish farms, said she caught some herring with similar symptoms in beach seine nets in 2011, but was unable to get DFO to investigate.
The problem seems much worse this time, she said, with all of the herring she caught in the recent netting showing disease signs.
"It was 100 per cent ... I couldn't find any that weren't bleeding to some degree. And they were schooling with young sockeye," said Ms. Morton, who suspects the disease is viral hemorrhagic septicemia virus.
Dr. Gary Marty, fish pathologist with the animal health centre for the B.C. Ministry of Environment, said VHSV and a second disease, viral erythrocytic necrosis, or VEN, are the two most likely suspects.
But he said both diseases have been on the West Coast for a long time and it is too soon to ring any alarm bells.
He said Ms. Morton could be seeing a common, localized outbreak that might just fade away.
"You'd have to have more information or more fish dying" before concluding there is a serious disease outbreak, Dr. Marty said.
"There has been ... research that shows it probably remains in the [herring] population all the time, but at a very low level. So in that sense it would be similar to influenza in people or just a cold virus in people," he said. "It will affect the population in late winter and early spring and then as the fish get more food available in the summer their condition improves and the virus goes away."
Dr. Marty said limited outbreaks of the two diseases are not necessarily a bad thing.
"In some respect for the population it's actually good to have small outbreaks, often because even though it may kill a few individual fish, the survivors are then immune from the disease and actually the population can be stronger as a result," he said.
Dr. Marty said he was aware of Ms. Morton's catch of apparently diseased herring, but hadn't been officially notified by DFO of the incident and had not begun any research himself.
DFO officials weren't available for comment Monday.
Lorena Hamer, a spokesperson for the Herring Conservation and Research Society, a non-profit founded by the herring fishing industry, said the symptoms described by Ms. Morton sound like VHSV but scientific confirmation is needed.
"I do hope that DFO is following up on this – it would be good to get confirmation of the disease, and more information on the extent of the infection," Ms. Hamer said in an e-mail.
She noted that a paper published in a recent issue of the international journal Veterinary Microbiology indicates that VHSV is a disease that can spread between species.
The paper, by researchers from Canada's Pacific Biological Station, in Nanaimo, and the U.S. Western Fisheries Research Center in Washington State, states that farmed Atlantic salmon can develop VHS and transmit it to Pacific herring.
"Viral hemorrhagic septicemia is considered a serious disease of wild Pacific herring, causing large scale fish kills," states the paper.