A fresh look at farmed vs. wild.
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More on the Environmental Impact of Farmed Salmon
An emphatic illustration of this emerged as I was writing this article. This one involved sea lice. Sea lice routinely parasitize wild adult salmon without killing them. But because the lice can’t live in fresh water, they die as the wild fish move upstream to spawn, leaving juvenile salmon unmolested during their early growth periods in the stream. Even after they enter the sea, young salmon usually run into sea lice only occasionally, at exposures they can handle.
But sea lice infest salmon farms heavily, thriving in the crowded conditions. We knew this 20 years ago, but were told they wouldn’t spread to wild populations. By 10 years ago research had proven that the lice did spread to wild populations, and by five years ago we knew that high concentrations of lice from fish farms were killing some wild fish.
But did they kill enough salmon to harm whole populations? The industry said “No.” But a paper in the journal Science published last December demonstrated convincingly that sea lice from salmon farms in British Columbia’s Broughton archipelago, a collection of islands and channels between North Vancouver Island and the mainland, are exterminating entire native runs of pink salmon.
The salmon industry at Broughton mirrors the industry’s worldwide development. Broughton got its first farms in the late 1980s, and by 2005 it had over 20 farms holding millions of Atlantics. These farms were releasing tens of millions of sea lice. Over the past five years these sea lice, floating in great density in the channels in which the salmon farms float, have forced virtually every pink salmon leaving the Broughton archipelago to swim through an infested gauntlet to try to reach the ocean. The wild pink fingerlings, their skin still unscaled, pick up two, three, a half-dozen lice apiece—tolerable to adults, perhaps, but not to these finger-sized smolts. “They are not equipped to survive this,” says Alexandra Morton, director of the Salmon Coast Field Station and a co-author of the paper, “and they don’t.” This infestation is wiping out the wild pink salmon runs whose rivers flow from the mainland into the Broughton archipelago. Analysis of returns and comparisons to nearby rivers without farms show the lice are killing 80 percent of the pinks that run the sea-lice gauntlet. At that rate, and with the pinks’ two-year-long life cycle, the several river populations of pink salmon that must run the Broughton gauntlet could be 99 percent extinct by 2011.