On the front page of today's Globe and Mail (Canada), it is reported that the BC sockeye salmon population has "mysteriously" collapsed to a record low for the second summer in three, eliciting international concern among scientists that the species’ long-term survival is threatened. An estimated 10.6-13 million sockeye were expected to return to the Fraser Valley this summer. However, the official count according to the Department of Fisheries and Oceans (DFO) is that only a paltry 1.7 million have returned.
Causes:
Ocean temperatures have risen substantially over the past years and researchers state that, “Warm water can affect things like food availability for the fish... [whereas] sockeye are plankton feeders, and plankton of the west coast of B.C. tend to thrive when conditions are cold.” On Aug. 10, the Fraser River temperature was 18.8 C at Qualark Creek, BC, 1.1 degrees higher than the average for that date. As such, "water temperatures in this range may stress migrating sockeye and slow their upstream migration" the US-Canada Pacific Salmon Commission said.
Sea lice that flourish near fish farms are another possible source of decline. "The parasites are known to latch onto young wild salmon heading into the sea and are suspected as a factor in the decline of other wild-salmon populations" along the BC coast.
Alexandra Morton, who several years ago correctly predicted a collapse of pink salmon runs in the Broughton Archipelago because of sea lice infestations, in March warned the same thing could happen to Fraser sockeye. She said researchers used genetic analyses to show Fraser sockeye smolts were getting infested with sea lice in Georgia Strait.
It is too early to ascertain if the current sockeye collapse will be repeated with other species that are expected to return this year; notably pink salmon which are projected to number 17 million.
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