Investigating salmon mysteries on the high seas

Canada’s National Observer –

On a late night last February, oceanographer Brian Hunt walked onto the deck of the RV Professor Kaganovskiy and looked out upon the unseasonably calm waters of the Gulf of Alaska. What he saw in the night ocean surprised him: the ship was surrounded by glowing golden jellyfish, their bell-shaped hoods illuminated by the ship’s floodlights.

It was a “mega swarm” of Chrysaora melanaster, also known as the northern sea nettle. They’re a species of jellyfish often found in the Bering Sea, with heads the size of dinner plates and stinging tentacles that trail for three metres.

“I never expected to see that,” says Hunt, who has participated in research expeditions covering five oceans. “I’ve seen jellyfish mega swarms in coastal waters several times, but I have never seen anything like that in the open ocean. It was a phenomenon.”

Hunt, an assistant professor of oceanography at UBC’s Institute for the Oceans and Fisheries, was part of a team of 21 international fisheries researchers on the Russian research ship—all trying to understand better why some salmon survive their time at sea, and some don’t.

Northern sea nettles have a voracious appetite for the same small aquatic creatures on which many salmon also rely. Their presence in these waters about 1500 kilometres from Vancouver added to researchers’ questions about the survival of the estimated 55 million Pacific salmon present in this part of the northeast Pacific.

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