Acoustic device may save India's river dolphins (BBC)

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NEW DELHI, India (Reuters) -- Japanese technology to track and monitor the behavior of India's endangered Ganges River Dolphins using underwater acoustics will play a vital role in efforts to conserve the freshwater mammals, the WWF-India said.

The Gangetic cetaceans are one of only four species of dolphins in the world which inhabit rivers and lakes and are much less common than their marine counterparts, numbering only around 2,000 in India, according to the conservation group.

Over the last 25 years, their numbers have halved -- trapped in fishing nets, hunted for oil, dead from pollution or the construction of dams along the Ganges river which stretches from the northern Himalayas to India's east.

WWF-India said researchers from the University of Tokyo have developed an underwater acoustic device or hydrophone which measures the individual sonar pulses or the clicking sounds emitted by the dolphins which are as unique as fingerprints.

From this, they can locate the dolphin and track its movements.
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more: http://www.cnn.com/2007/TECH/science/02/09/river.dolphins.reut/index.html