Fish & Wildlife | Ecotrope

‘Genius’: Using sound to see deep into the ocean

Ecotrope | Sept. 28, 2010 2:11 a.m. | Updated: Feb. 19, 2013 1:46 p.m.

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Oregon State University Associate Professor of Oceanography Kelly Benoit-Bird has won a so-called ‘genius’ grant - a highly prestigious and out-of-the-blue award from the MacArthur Foundation that comes with a half-million dollars, no strings attached. (More on how she kept the news a secret)

I reported on a presentation by Benoit-Bird in Astoria earlier this year and was amazed by her findings on the feeding habits of ocean creatures. By using advanced sonar technology to create pictures of underwater movements, she’s uncovered unique feeding patterns in salmon, sardines, giant squid and spinner dolphins.

Without employing sonar technology, she explained, scientists never would have discovered the incredible, communal, nighttime feeding methods the dolphins use to survive on 2-inch lantern fish in the central Pacific. Here’s what I reported in The Daily Astorian:

Benoit-Bird has used sonar to document the nighttime feeding habits of spinner dolphins in the central Pacific ocean, illustrating an orchestrated group movement to encircle and concentrate pools of 2-inch lantern fish for easier feeding.

During the day, the spinner dolphins socialize near shore where it’s easier to spot their predators. They wait for illuminated lantern fish to migrate toward the water’s surface at night and then they collectively move out to feed.

The dolphins have a limited amount of time to feed on the lantern fish and high energy needs to satisfy. To survive, “they need to eat an awful lot of those fish,” said Benoit-Bird. “It would be like us trying to survive on popcorn that’s constantly moving away from us.”

Her sonar tracked the pod of dolphins pairing up and swimming in a circular formation to herd their prey into dense patches. Then, one by one, they took turns feeding in the thickly pooled food. But they only had about five minutes to complete the exercise before they all had to return to the surface for air.

To coordinate the movements, Benoit-Bird noted, the dolphins used their own form of sonar communication to line themselves up and arrange the circular swimming pattern.

Without employing similar sonar techniques, scientists wouldn’t be able to document this nighttime phenomenon, she said.

“We rarely get a chance to see them at night except on calm seas with a full moon,” she said. “The use of sound has allowed us to see how it works.”

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