A four-year study headed by Fisheries and Oceans Canada (DFO) has detailed a peculiar phenomenon in British Columbia’s waters: an unknown virus may be killing off large numbers of Fraser sockeye salmon.
In studying B.C.’s renowned Fraser River sockeye, DFO researchers tracked adult salmon in the ocean and river to determine if successful and unsuccessful spawners were physiologically distinguishable prior to reaching the Fraser River.
The results of the study, published in the journal Science, indicate that ocean-tagged salmon “showing a certain gene expression signature” were 13.5 percent more likely to die before spawning than healthy fish, with river-tagged salmon 50 percent more likely to die before spawning.
“This study indicates that disease present in the fish before they enter the river may be impacting spawning success,” said University of British Columbia’s Scott Hinch, a co-author of the study.
The researchers didn’t identify the virus, but suggest it may be related to leukemia or lymphoma.
Biologist and fish farm opponent Alexandra Morton believes it could be salmon leukemia originating from farmed salmon.
“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,” Morton said.
Morton cites DFO studies from the 1990s that documented salmon leukemia in Chinook salmon farms and found it could infect Atlantic and sockeye salmon.
“Did this virus start in the wild, become amplified in the farm Chinook, and mutate to infect the millions of nearby introduced Atlantic salmon altering it to become unidentifiable?” Morton wonders.
Sockeye salmon have been in decline since the early 1990s, and in 2009 the Fraser River sockeye run reached an all-time low.
But in a stunning turn of events in 2010, 35 million salmon returned to the river—the healthiest run in almost 100 years and a stark contrast to the previous year’s meagre return of 1.5 million.
However, some scientists say the sudden 2010 boom was an isolated phenomenon most likely caused by a volcanic eruption in Alaska in 2008, and shouldn’t be seen as a sign that the Fraser runs are out of trouble.
During the eruption, iron content in falling ash may have fertilized phytoplankton that live in the ocean, allowing it to reproduce rapidly. This abundance in the food chain helped the salmon grow in record numbers, producing the 2010 record run.
In November 2009 Prime Minister Stephen Harper ordered a judicial inquiry into the collapse of the Fraser sockeye run. The Cohen Commission in Vancouver is also conducting an investigation into the issue.
Morton’s lawyers have asked the Cohen Commission to hold a special portion of the hearing to look into whether this potential virus is impacting wild sockeye and whether it is a mutated form of salmon leukemia.
One stock of Fraser sockeye, the Harrison sockeye, has not been “on the rollercoaster of decline and boom,” according to Morton.
The Harrison sockeye have been steadily increasing over the past 18 years, and Morton believes it’s because they migrate to sea via southern Vancouver Island rather than through the salmon farms of eastern Vancouver Island.
Morton has long maintained that B.C.’s approximately 130 open net-cage salmon feedlots—particularly those in the Georgia Strait, between the mainland and Vancouver Island—are negatively impacting wild stocks, including through the spread of sea lice.
The BC Salmon Farmers Association, however, says that even when in full operation, fish farms are no threat to wild migrating salmon, and that sea lice numbers are managed and maintained below regulation levels.