Scientists seek to learn whether fish farms kill fish

Mark Hume
February 5, 2012
Globe and Mail

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.

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