By Phil McKenna
A new sonic alarm could warn off whales and manatees threatened by approaching ships. Endangered North Atlantic right whales are especially at risk from collisions – only about 350 remain, and at least a third of all right whale deaths over the last decade were due to ship strikes.
A team of researchers at Florida Atlantic University believes that many collisions occur because there is region in front of moving ships where propeller sounds are blocked.
"If the ship is wide enough, the sound of the propellers is deflected off to the sides," says Edmund Gerstein, who presents his team's findings this week to the Acoustical Society of America.
Gerstein notes that individual manatees in Florida have been hit as many as 50 times by boats. "They seem to actually seek out the quieter zone in front of the ship as a refuge," he says.
So he and his colleagues developed a small device to fit on the bow of a ship below the waterline, which emits sound waves focused into a narrow beam. Gerstein says that in preliminary testing of the device, manatees always changed course to avoid the approaching ships. …
Sonic alarm saves marine mammals from ship strike
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