After three years of unprecedented warm water along the U.S. West Coast, sea temperatures in 2017 had finally cooled. Fat shrimplike krill had returned and again were providing rich meals for salmon. Sea lions and other marine mammals were no longer washing

By Craig Welch National Geographic 6-13-17

ashore shriveled and starving. Things appeared to be getting back to normal.

Then they showed up.

Beginning this spring, millions of bizarre primitive-seeming jellyfish-like bioluminescent sea creatures—some more than two feet long—started gumming up research nets, glomming onto fishing hooks, and cascading onto beaches along the West Coast.

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