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Mark Hume

Scientists seek to learn whether fish farms kill fish Add to ...

A group of leading fisheries scientists have come up with a proposal to answer some of the most pressing and difficult environmental questions on the West Coast: Are fish farms killing wild salmon? And if so, how many?

Debate on the environmental impact of fish farms has raged in British Columbia for over a decade. Environmentalists blame aquaculture for causing a collapse in wild salmon populations by spreading sea lice and disease, but there has never been any hard scientific evidence to prove those claims.

Now David Welch, who has done groundbreaking work tracking fish at sea with acoustic transmitters, has put together a team of some of the brightest fisheries researchers in Canada to solve the mystery.

Dr. Welch testified last year to the Cohen Commission, explaining how his acoustical tracking work had shown that salmon smolts, in their first year at sea, were vanishing in Queen Charlotte Strait, just past the northern tip of Vancouver Island.

Because fish farms are clustered in a bottleneck in Discovery Passage on the northeast coast of Vancouver Island, Dr. Welch’s research raised suspicions that wild salmon might be picking up diseases and/or lice as they migrated past the farms, then dying some weeks later in Queen Charlotte Sound.

In December, Dr. Welch filed a supplemental report with the Cohen Commission, saying a new analysis shows his data is even stronger than he first thought. So many fish died north of the farms, he stated, that it could explain the Fraser River’s catastrophic sockeye collapse in 2009, when only one million fish returned to spawn, instead of 10 million.

“This level of higher mortality would be sufficient to fully explain the 10-fold decline in Fraser sockeye survival seen since 1990,” states Dr. Welch.

He cautions that “this new result remains a correlation, not proof that the fish farms caused the reduced survival,” but he proposes a way to find out.

Working with several prominent researchers – including Scott Hinch of the University of British Columbia and Kristi Miller of the Department of Fisheries and Oceans – he proposes to tag thousands of salmon smolts with acoustic transmitters and to track them up the coast, past the fish farms and deep into Queen Charlotte Sound.

The researchers would use control groups, including fish held in pens near fish farms, as well as fish released in pristine areas where they cannot come into contact with farms.

“Whether fish farming caused the widespread decline of southern British Columbia salmon stocks is hotly debated, and it is unlikely that evidence reported at the Cohen Judicial Inquiry can resolve the controversy,” Dr. Welch writes in an overview of his proposal. “[But]if fish farms reduce survival by disease transfer, parasite load, or some unknown agent, then there should be a measurable decline in survival of the exposed smolts relative to controls.”

He says the project should not only show whether fish farms are killing salmon – but how many salmon are killed.

“We believe that the statistical power of the design we have identified is high enough that by the end of 3-5 years a clear decision can be made about whether fish-farm impacts are unacceptably large and the industry should be regulated to minimize interaction with wild stocks,” writes Dr. Welch.

Several fisheries scientists have written letters of support that have been filed with the Cohen Commission.

Steven Cooke, Canada Research Chair in Fish Ecology at Carleton University, states the study is sorely needed to finally settle the issue of whether fish farms are to blame for wild salmon declines.

Paul LeBlond, Professor Emeritus at UBC, writes that the study “could save years of further bickering” over the fish-farm issue.

And Neil Frazer, Professor of Geophysics at the University of Hawaii, states that Dr. Welch’s work marks “a watershed in fisheries research” because his methods “turn fish into moving reporters on the marine environment.”

To do the study, Dr. Welch needs $3-million a year in funding for up to five years. That’s a lot of money – but it’s not much when you consider that Dr. Welch could end the war over fish farms and provide the scientific base that government needs to properly regulate the industry.

That’s a deal worth fishing for.

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