Fascinating if discouraging report in the Washington Post (via the Boston Globe) on how a trend of salmon not returning to their rivers and streams to spawn could be a climate change effect. Here’s more from Post reporter Joshua Partlow:
“Salmon will go out, in what we think is a really good ocean, and then it collapses,” said Weitkamp, a fisheries biologist with the National Oceanographic and Atmospheric Administration based in Oregon. “They don’t come back.”
The pressures salmon face in their home rivers, and their experience in coastal waters, are well documented. But less is known about what they endure on the high seas. It is there where some species of salmon spend several years before returning to spawn — and where Weitkamp said many are dying as marine heat waves driven by climate change are altering their ecosystem.
“Once they leave that coastal area, that’s where they enter the black box,” she said.
The largest-ever salmon research expedition in the North Pacific, now underway, aims to shed light on that stage in the salmon life cycle. Five ships from the United States, Canada, and Russia have been collecting salmon samples and studying ocean conditions across about a million square miles. Researchers hope to map where salmon from different rivers spend their winter months — when less food is available and they are particularly vulnerable — and detect signs of competition between salmon species following marine heat waves in recent years.
“We’ve seen dramatic or severe declines in many of our salmon stocks,” said Jackie King, chief scientist on the Canadian research ship the Sir John Franklin. “There is a high mortality rate in the ocean, and that seems to be one of the toughest things for us to estimate.”