"Fish farms could push Pacific salmon to extincion" a study said.
A groundbreaking scientific study has today established for the first time a large-scale and deadly link between fish farms and sea lice infestations that threatens to wipe out entire populations of wild Pacific salmon.
An article to be published in Friday's edition of Science, one of the world's foremost scientific journals, says wild pink salmon runs on the British Columbia central coast will be extinct in as little as four years because of a cluster of salmon farms that are creating lethal infestations of sea lice in that area.
The article's authors, including University of Alberta researcher Martin Krkosek and B.C.'s Alexandra Morton, looked at 37 years' worth of Fisheries and Oceans data for 71 central coast rivers and found that wild pink runs have comfortably withstood decades of commercial fishing -- but cannot survive fish farms.
"We have seen is a very rapid four year decline in the pink salmon populations in the Broughton," Mr. Krkosek said in an interview earlier this week.
"Based on that measured rate of decline, which is real, we can expect that in another four years those fish will be all gone if the sea lice infestations continue."
The situation has become acute since 2000 as the salmon farming industry has increased the volumes of fish it produces at its farms.
The situation has implications for grizzly bears, killer whales and numerous other species -- even trees along streams -- that rely on pinks as a major source of food or nutrients.
Sea lice hyper-concentrate around the farms and spread to wild salmon migrating in the vicinity of the farms. The lice may not be lethal to adult fish, but they're deadly for infant pink salmon making the transition to the ocean from their natal streams.
The article says the situation is particularly acute for wild pinks on the central coast around the Broughton Archipelago, which has the greatest concentration of salmon farms in B.C.
The report says lice infestation rates are 70 times higher among juvenile pink salmon on central coast rivers compared to infestations in fish farm-free areas farther north.
It also says mortality rates among juvenile pinks infested with sea lice "is commonly over 80 per cent."
"If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon abundance is expected in four pink salmon generations," the article says.
The study brings an element of finality to the debate about the threat salmon farms pose to wild fish. It also puts Canada's federal and provincial governments, and the salmon farming industry, at odds with the reigning body of opinion in the global scientific community.
Only last summer, the Vancouver Sun reported that a B.C. government-financed fisheries research group had suppressed a report on links between sea lice and declining wild fish populations.
At the time, a senior federal fisheries scientist government stated in the Sun story that there was no evidence that sea lice from fish farms are having population-level impacts on wild fish.
The notion that farm-caused lice infestations may harm individual fish, but pose no extinction threat to entire populations, is the underpinning of the governments' resistance to tighter controls on salmon farming.
On the premise that there are no population-level threats, both B.C. and Canada have resisted calls from environmental groups to move farms away from salmon-migration areas, or to ban the practice of raising salmon in open-net sea pens that allow transfer of disease to wild fish.
That argument has been fundamental to worldwide resistance by the salmon farming industry of any improvement of its methods. But it now appears that argument can no longer withstand critical scrutiny.
Mr. Krkosek said the article's authors chose to study pink salmon because they have the simplest, easy-to-track life cycle of any of five Pacific salmon species. That made it easy to discern and formalize for the first time the connection between fish farms and wild salmon extinction threats, he said.
"One of the things that has really plagued research on sea lice and salmon and has made it very difficult, in fact impossible until now, to measure the impact of sea lice on wild salmon populations is that they are hard to study," Mr. Krkosek said.
"These kind of problems have been known for decades, especially in Europe but still today it's not clear if sea lice have had an impact on the populations.
"Pink salmon are abundant enough, they have a short enough life cycle, they are predictable in their migration behavior, they have enough characteristics to let us study them in the level of detail that's necessary to actually measure the impact of sea lice on the populations."
According to a University of Washington fisheries professor who reviewed the Science article prior to publication, the calculations linking salmon farms to wild salmon extinctions are simple and straightforward.
"This is pretty good evidence that there are population-level impacts. In the past individual impacts were noted -- fish swim by farms and get sea lice, you hold them in pens and they die," said Mr. Hilborn, formerly a Vancouver-based scientist with Environment Canada who is now a professor of fisheries management at U. of Washington.
Mr. Hilborn predicted that government will find the issue difficult to resolve, regardless of the extinction threats, because the B.C. salmon farming industry is a big employment and revenue generator for the province.
"If I was the B.C. minister of fisheries and I was considering if I was going to shut down this big industry to rebuild these 15 streams it wouldn't be a clear call," Mr. Hilborn said. "It's just another piece of evidence that if you produce these high density [farm] populations you are going to be a source of pathogens -- and that they have population-level impacts."
Mr. Hilborn reviewed the calculations in the paper and said "it's exactly what I would have suggested doing. It's not any kind of complicated analysis. You just look at the rate of change from one generation to another."
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