Nicholas Makris didn't set out to count fish. His original goal was to locate ancient riverbeds under the ocean floor.
But the team on which this MIT professor worked soon realized that the new sonar technique they were using allowed them to see enormous schools of fish. In fact, by using low frequency sound waves - which travel great distances - this method can study fish over an area a million times larger than previous techniques allowed.
Makris is the lead author of a new article in the journal Science. The article reports that researchers can now gain an accurate picture of fish over a 4,000 square mile area. Previous methods relied on snapshots of 120 square yard areas.
"It would be like watching 'Casablanca' and you're seeing one pixel moving across the screen, and that's all you get," explained Makris. "You can't figure out what's going on, it's way too slow."
The MIT team was surprised to discover one shoal of fish that was six to nine miles long.
This new method is important because it allows researchers to better understand fish populations, so that nations can balance the need to guard fish stocks while enabling commercial fleets to operate in a sustainable manner.
"The world's fish stocks are being depleted at a horrible rate," said Makris, "One of the reasons (for the inaccurate counts) is the darkness in the ocean. You don't know what's going on."
Co-authors on the paper are Purnima Ratilal (Ph.D. 2002) of Northeastern University; Deanelle Symonds, Srinivasan Jagannathan and Sunwoong Lee of MIT's Center for Ocean Engineering; and Redwood Nero of the Naval Research Laboratory.
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