Better tool for counting fish
Researchers at MIT, Northeastern University and the Naval Research Laboratory have for the first time used a low-frequency sonar remote system to track fish populations and scan vast sections of the ocean. For example, the scientists were able to spot a vast shoal of fish only 120 miles from New York City. This method is far better than current ones, which involves slow-moving vessels and high-frequency sonar beams which quickly disappear into the ocean. With this method, government agencies will be able to accurately check if fish populations are really declining or not -- and to protect them.
Here is a comparison between this new method for counting fish and the traditional one.
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.
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.
According to the researchers, this new method works best along the continental shelf, so they started by investigating the waters south of Long Island, New York. And they got a big surprise when they found a huge shoal of fish, about 10 to 15 kilometers long.
Below are several sonar images showing this fish shoal located near the edge of the continental shelf south of Long Island, N.Y. (Credit: Makris, Ratilal, Symonds, Jagannathan, Lee).
Then, as the receiver ship turned, the images were slightly different (Credit: Makris, Ratilal, Symonds, Jagannathan, Lee).
You can find more explanations and a diagram showing how the source and the receiver ships were collaborating on this page.
But how will this help to control and protect the fish populations?
The new sensor system 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."
And in "Better Tool for Counting Fish May Help Protect Population," the Wall Street Journal agrees (Paid registration needed).
"I think this is potentially revolutionary," says Jesse Ausubel, a New York program director for the Census of Marine Life, an international effort begun five years ago to count the world's fish. "This is the kind of technology that allows wise regulation, because a lot of dispute in the ocean has to do with what is there."
The Wall Street Journal also raises an interesting question about this technology.
Some marine scientists worry that the new technology could fall into the hands of poachers. The researchers say that scenario is unlikely, because the equipment is both complex to use and expensive, costing as much as $1 million. Still, skeptics say, the value of hitting mother lodes of fish would more than offset the expense of the equipment.
And for more information, this research work has been published by Science under the title "Fish Population and Behavior Revealed by Instantaneous Continental Shelf-Scale Imaging" (Vol. 311, No. 5761, Pages. 660 - 663, February 3, 2006). Here are several links to the abstract, some additional figures and a movie (37 seconds, 56.4 MB) from which the above images have been extracted.
Sources: Massachusetts Institute of Technology news release, via EurekAlert!, February 2, 2006; Jim Carlton, The Wall Street Journal, February 3, 2006; Science, February 3, 2006; and various web sites
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