( Researchers at MIT have found a new way...)One fish, two fish: New MIT sensor improves fish counts

A remote sensor system developed by Associate Professor Nicholas Makris of mechanical engineering, along with others at MIT, Northeastern University and the Naval Research Laboratory, allows scientists to track enormous fish populations, or shoals, as well as small schools, over a 10,000-square-kilometer area - a vast improvement over conventional technology that can survey only about 100 square meters at a time.

"We're able to see for the first time what a large group of fish looks like," said Makris, who compared the dramatic improvement to the difference between seeing everything on a television screen and seeing only one pixel.

The new sensor system, described in the Feb. 3 issue of Science, could allow government agencies to figure out what's really happening to fish populations, which many environmentalists and scientists believe are in rapid decline.

"The world's fish stocks are being depleted at a horrible rate," said Makris, who attributed declining populations to overfishing, a problem that has been abetted by inaccurate fish counts. "One of the reasons (for the inaccurate counts) is the darkness in the ocean. You don't know what's going on."

Current surveying methods depend on highly localized observations taken from slow-moving research vessels, which provide only a small amount of data about a large shoal, Makris said. "It would be like watching 'Casablanca' and you're seeing one pixel moving across the screen, and that's all you get. You can't figure out what's going on, it's way too slow," he said.

Both the new and old methods rely on sonar, which locates objects by bouncing sound waves off of them. With the old technique, survey vessels send high-frequency sonar beams into the ocean, where they dissipate much like the light from a flashlight shining
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Source:Massachusetts Institute of Technology