Scientists Develop New 'Super Fish Finder' Sonar

MICHELE NORRIS, host:

Sonar has been around for a long time. Fisherman and scientists use it to look into the depths of the ocean. It makes crude maps by bouncing sound waves off underwater objects. Traditionally sonar has worked like a flashlight on a moonless night, lighting up only bits and pieces of the underwater landscape. But now there's a new kind of sonar.

According to the journal Science, it maps entire underwater landscapes along with the fish swimming over them. As NPR's John Nielsen reports scientists say the new device could be a breakthrough or a curse.

JOHN NIELSEN reporting:

Not too long ago, a research boat from the Massachusetts Institute of Technology towed a strange looking object up and down the Eastern Seaboard. It looked a little like a satellite dish pointed down toward the sea floor. Nicholas Makris, an oceanographer from MIT, says the device makes old fashion sonar maps look like they were drawn with crayons.

Mr. NICHOLAS MAKRIS (Massachusetts Institute of Technology, Oceanographer): We're able to send a sound wave out omni-directionally 360 degrees. And within about a minute, we can get an image of that whole area.

NIELSEN: The image is a three dimensional map that covers several hundred cubic miles. That's much better than the sketchy maps you get from old style sonar. Maps that force scientists and fisherman to guess at what's in the blank spots. Makris says the new maps eliminate the guess work. They also make it possible to follow moving schools of fish.

Mr. MAKRIS: We recreate the actual motion that's going on in the ocean by taking a lot of these snapshots every minute or so. And we make a movie of what's happening over this huge, huge area. And we're seeing things that no one has ever seen before.

NIELSEN: For example, on its very first run, the new sonar picked up an uneven line of 10 to 20 million fish stretched out for miles off the coast of New England.

Mr. MAKRIS: And when you look with our method, you see that it's a lot of population centers that are connected with fish bridges between each of them.

NIELSEN: Sort of a society down there?

Mr. MAKRIS: Exactly. A society with population centers and they're kind of banging into each other as they kind of wander, meander around.

NIELSEN: Oceanographers and government officials are now lining up to use this super sonar. Fishermen are also interested which could turn out to be a problem.

Mr. PETER ETNOYER: (Oceanographer, Los Angeles County Museum of Natural History): This is very exciting technology but it does cause some concern because it looks like they've built a better mousetrap. And one of the last things we really need right now is a better way to catch fish.

NIELSEN: Oceanographer Peter Etnoyer works with the Los Angeles County Museum of Natural History. He worries that the new fish finder could add to over-fishing problems. But this new device could also help protect fish by helping regulators find the key breeding zones.

Steve Morowski, Chief Scientist at the National Marine Fisheries Service, says his agency badly needs a way to see more of what's going on down there.

Mr. STEVE MOROWSKI (Chief Scientist, National Marine Fishery Service): Remember that the United States has about four point million square miles underwater, and we're trying to assess about 900 different species of fish, and marine mammal species.

NIELSEN: Don't expect to be able to buy a super sonar for your bass boat any time soon. According to Makris, there's only one in existence. It cost several million dollars to build, and its not for sale. John Nielsen, NPR News, Washington.

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