The Pacific Blob and Climate’s Cost to Cod

November 8, 2017

Seattle Times:

Gulf of Alaska cod populations appear to have nose-dived, a collapse fishery scientists believe is linked to warm water temperatures known as “the blob” that peaked in 2015.

The decline is expected to substantially reduce the Gulf cod harvests that in recent years have been worth — before processing — more than $50 million to Northwest and Alaska fishermen who catch them with nets, pot traps and baited hooks set along the sea bottom.

The blob also could foreshadow the effects of climate change on the marine ecosystem off Alaska’s coast, where chilly waters rich with food sustain North America’s richest fisheries.

Federal fisheries biologist Steve Barbeaux says that the warm water, which has spread to depths of more than 1,000 feet, hit the cod like a kind of double-whammy. Higher temperatures sped up the rate at which young cod burned calories while reducing the food available for the cod to consume.

“They get weak and die or get eaten by something else,” said Barbeaux, who in October presented preliminary survey findings to scientists and industry officials at an Anchorage meeting of the North Pacific Fishery Management Council. The 2017 trawl net survey found the lowest numbers of cod on record, more than 70 percent lower than the survey found two years earlier.

Barbeaux said the cod decline likely resulted from the blob, a huge influx of warm Pacific Ocean water that stretched — during its 2015 peak — from the Gulf of Alaska to California’s offshore waters.

Biologists tracked increases in bird die-offs, whale strandings and other events such as toxic algae blooms. Even today, its effects appear to linger, such as in the dismal survey results for salmon this past summer off Oregon and Washington.

Scientists don’t ascribe the blob specifically to climate change. Gulf of Alaska temperatures — influenced by atmospheric conditions such as wind strengths — have always fluctuated over time.

But researchers have never before tracked such an extreme heat wave that spread across such distances and penetrated to such depths. And the blob, though now easing, is likely a preview of ocean temperatures expected later in the century as climate change intensifies.

Climate scientists note that ocean temperatures are on the rise as the water absorbs most of the heat trapped by greenhouse gases in the atmosphere.

 

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