Salmon samples outside B.C. farm pens test positive for PRV, biologist says

In a news release, Morton said she believes “this work is critical to the survival of wild salmon and whales on the B.C. coast.”

While the vast majority — 79 per cent — of salmon harvested in B.C. is farmed, the wild salmon commercial fishery remains significant, with a wholesale value of $206.9 million for the processed product in 2016. The wholesale value of processed farmed salmon was $796.6 million. Combined, that’s more than a $1-billion value.

Over the course of the summer, and in co-operation with the U.S.-based advocacy group Sea Shepherd Conservation Society, Morton took three sets of samples outside the pens of 27 salmon farms in B.C. The results she released Wednesday — part of her ongoing research into open-net pen fish farms, sea lice, viruses and declining salmon populations — include just the first round of samples from five farms in the Discovery Islands.

But according to Shawn Hall, a spokesperson for the B.C. Salmon Farmers Association, “it’s not a surprise and it’s not a concern” that PRV was detected at the farms.

The virus, he said, is rarely detected at hatcheries in B.C. and instead is contracted in the marine environment. He added that it does not appear to cause disease.

A recent review of the piscine reovirus in processing plant waste water conducted for the B.C. government notes the virus is endemic in Pacific salmon species and likely existed before the Atlantic salmon farming was introduced.

The review also notes that PRV hasn’t yet been shown to cause heart and skeletal muscle inflammation in B.C.

Fisheries and Oceans Canada scientist Kristi Miller-Saunders however, said it’s established that the virus causes heart and skeletal muscle inflammation in Atlantic salmon.

In a recent study and she and her colleagues found the virus is also associated with jaundice or anemia in Chinook salmon. Though, because it was a field-based study, it does not prove the virus causes these health impacts in the salmon, she added.

They found that even when there was no evidence of disease, the virus remained in the red blood cells of both species, where it replicated to high numbers, she explained in an email.

“In Atlantic salmon, the virus begins to leak out of the red blood cells in some fish when it reaches high abundance, and infects cells in the heart and skeletal muscle,” Miller-Saunders said.

“In Chinook salmon, when the virus reaches high levels, the red blood cells rupture, releasing the virus and hemoglobin — the protein that carries oxygen to the tissues and is toxic when outside of red blood cells at high levels.”

In Chinook, most of the virus is found in the kidney and liver and Miller-Saunders said she believes it’s the “toxic overload of hemoglobin” that results in the jaundice.

An assessment of the study Miller-Saunders co-authored by another Fisheries and Oceans agency raised concerns about the data and the criteria the authors used to characterize jaundice. The assessment — which it notes should not be considered peer-reviewed scientific advice but was done rapidly — ultimately recommended the federal department not change its policies which currently allow salmon smolts infected with PRV to be put into ocean pens.

On Wednesday, Miller-Saunders said the precautionary principle would suggest the virus does present a risk to Chinook salmon and likely Coho.

Though “the jury is still out on whether PRV can cause disease in other Pacific salmon species in B.C.,” she said.

Hall, a spokesperson for the salmon farming industry said, “B.C.’s salmon farmers are passionate about wild salmon and committed to engaging in ongoing research and science, and making adjustments based on what we learn.”