This summer, the marine activist organization Sea Shepherd Society launched its "Virus Hunter campaign" on the northeastern coast of Vancouver Island, in the Broughton Archipelago.

Sea Shepherd is known for extreme environmental battles, going back to its founder Paul Watson – who defected from Greenpeace because he found their environmental resistance too tame.

W5's profile on Paul Watson: Modern pirate seeks to protect world's sea life

Flying the skull and crossbones on the spinnaker, their 81-foot research vessel Martin Sheen (yes, named after the actor who is a supporter) sailed up the B.C. coast to support biologist Alexander Morton.

Her crusade for the past 30 years has been to prove that salmon farms raising transplanted Atlantic salmon for market are the reason for declining wild Pacific salmon. Morton is trying to shut down B.C.'s $745-million salmon farm industry.

Atlantic salmon are a foreign species on Canada’s West Coast. They’re originally from Norway, but are now raised in open-ocean net pens at about 109 licensed farms by the millions of salmon each year. Environmentalists and critics complain that their existence here may be changing B.C.’s coastal waters forever.

PRV stands for Piscine Orthoreovirus. It is believed to cause the salmon disease Heart and Skeletal Muscle Inflammation, or HSMI, which causes heart lesions. In Norway, HSMI has caused farmed salmon mortality of up to 35 per cent. Detected in Canadian farmed salmon, PRV has also been found in wild salmon, but finding dead HSMI-infected wild salmon is difficult as these fish are easy prey.

“I’ve been watching this for years and it literally makes me feel ill,” says Morton, “because I know the majority of these fish are infected with PRV, a highly contagious blood virus.”

W5 joined Morton for a few days aboard the Martin Sheen, to watch her campaign against fish farms. She was trying to get video of sick and deformed fish and hoping to collect tissue samples to prove her contention that farmed Atlantic salmon is a dangerous, invasive species.

We travelled to Port McNeil, a small village five hours north of Victoria on the northeaster end of Vancouver Island. From there we sailed to a fish farm owned by the Norwegian company Marine Harvest. It’s the biggest of the fish farm operator on the B.C. coast.

After years of boarding the floating fish farms, Morton was charged with trespassing. Now, she has allied with B.C. First Nations, who claim the farms are trespassing on their unceded territory.

At one farm Morton met up with First Nation occupiers, who had built a camp and were refusing to leave until their title disputes were resolved. The protesters complain that wild salmon, their traditional food source, are dying off, and believe fish farms are the reason for the decline.

A few days later W5 was invited to see the other side of the story. We joined Ian Roberts, the spokesperson for Marine Harvest, as he took us to tour one of their floating fish farms.

Roberts showed us the massive operation, which produced up to 4,500 metric tonnes of Atlantic salmon each year. It’s big business -- stretching from the pens that support about three-quarters of a million salmon at each farm -- to the finished product you can find in most supermarkets and restaurants.

For its part the fish farm industry insists it’s not spreading disease into wild salmon populations and is not the reason for the decline of those native species. And, they argue, that fish farming is producing much needed seafood in a world where the oceans are no longer able to support demand.

A few weeks later we met up with Canada’s Fisheries Minister, Dominic LeBlanc, who insists that his department is committed to protecting wild salmon.

But, back on the Sea Shepherd ship, Alexandra Morton predicts a bleak future if the decline in wild salmon is not stopped. They are the so-called keystone species, which support orca, sea lions, seals, bears and eagles -- and even their rotting carcasses after spawning provide fertilizer for plant life -- all of which Morton insists are at risk without wild Pacific wild salmon.

Aboard the Martin Sheen, Alexandra Morton told W5: “I love this place. It’s painful in this day and age to be a biologist and watch the world around you be destroyed.”

KRISTI MILLER RESEARCH PAPER

Kristi Miller is the federal fisheries scientist who found HSMI in B.C. farmed salmon. Publication of her research article spurred debate about the effect of illnesses in farmed salmon can have on wild salmon.

Miller 2017 - Heart and skeletal muscle inflammation diagnosed on a British Columbia salmon farm

GARY MARTY RESEARCH PAPERS

Gary Marty, is the fish pathologist for the BC Ministry of Agriculture. He wrote two papers which downplayed the evidence of HSMI in farmed salmon in British Columbia.

Marty 2014 - Piscine reovirus in wild and farmed salmonids in British Columbia

Marty 2016 - PRV from Western North America is transmissible to Atlantic salmon and sockey salmon but failes to cause HSMI

MARINE HARVEST ANNUAL REPORT

Marine Harvest is a global company and the largest fish farm operator in BC waters.

Marine Harvest 2016 Annual Report

W5’s investigation of the controversy surround farmed salmon and the decline of native Pacific salmon airs Saturday.