Warm water blamed for lowest sockeye salmon run on record
'That affects the food web, the food that they eat, it may even affect their predators,' says SFU prof
Warm summer temperatures may have Lower Mainlanders feeling good, but they are proving lethal for sockeye salmon.
The Pacific Salmon Commission recently revised its already low forecast for sockeye numbers from 2.3 million to 1.1 million in the Fraser River, which would be the lowest number since records have been kept.
As of August 12, the DFO has suspended all sockeye fisheries in response.
Three main reasons
John Reynolds, professor of aquatic ecology and conservation at Simon Fraser University, said three main factors are contributing to this year's low numbers: a small parental generation; a "blob" of warm water in the Pacific Ocean; and higher-than-normal temperatures in the Fraser River.
Sockeye spawn over a four-year cycle, and Reynolds said the last cycle's already low numbers meant low numbers were a distinct possibility for this year.
But the problem has been compounded by warm water according to Reynolds who says a large mass of warm water off the south B.C. coast — referred to by scientists as "the blob" — is wreaking havoc on the sockeye's ecosystem as a whole.
"That affects the food web, the food that they eat, it may even affect their predators," Reynolds said. "So no one knew how it would affect these juvenile fish before they came back as adults, but nobody thought it was going to be good."
Furthermore, Reynolds said warm waters in the Fraser may kill salmon — a cold water fish by nature — as they travel upstream to spawn.
"As soon as temperatures in the Fraser go above about 18 or 19 degrees, adult fish start to die in the river," Reynolds said.
The Pacific Salmon Commission measured water in the Fraser to be 20.6 degrees C on August 18 — 2.5 degrees higher than average for that date.
Fisheries feeling effects
Reynolds says there's not much that can be done other than to back off on fisheries, which DFO has done.
According to a DFO release, commercial sockeye fisheries have been closed entirely. First Nations sockeye fisheries have been closed in marine areas and the lower Fraser River.
Recreational salmon fisheries have also been closed on the Lower Fraser for fear of harming the sockeye.
2013 saw historic lows for sockeye numbers in the Skeena River, resulting in the fishery being closed for the first time ever.
With files fromBrenna Rose.