AN UNMANNED submarine has been developed by Japanese marine engineers to automatically track down and follow pods of whales and shoals of tuna. While its inventor insists the vessel is intended for research, it is likely to alarm conservationists worried that it might help Japan鈥檚 controversial 鈥渟cientific鈥� whalers locate their prey.
The 3-metre-long seagoing robot has four underwater microphones or hydrophones mounted on the 鈥渨ings鈥� that control its motion through the water. From differences between sounds picked up by each hydrophone, an on-board computer works out where the sound is coming from. And by comparing the sound with stored recordings of various types of whale or tuna, it can home in on a particular species.
Once the sub has located a target, it can automatically follow a shoal or pod at a leisurely 1 to 2 knots (2 to 4 kilometres per hour) for 10 hours. In field tests near Japan鈥檚 Kerama Islands in March, researchers led by Tamaki Ura of the Institute of Industrial Science at Tokyo University successfully used the sub to track a pod of humpback whales.
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The tests began when hydrophones hanging from the research ship located a distant pod of whales. The sub then dived to about 50 metres and switched off its electric motors so that they would not drown out the whales鈥� faint song. 鈥淭he submarine automatically followed the sound and after an hour and a half came within 50 metres of the whale,鈥� says Ura.
The sub is intended for research, not hunting, Ura insists. Asked if it might be used in Japan鈥檚 scientific whaling programme in Antarctic waters, which critics say is a cover for the commercial exploitation of minke whales, Ura said: 鈥淚 know very little about the minke whale, so I can鈥檛 answer.鈥� It鈥檚 hard to track sea creatures using conventional diving equipment because it either has to be manned, or tethered to research ships.
鈥淔or intensive observation of whales, it is necessary to follow them closely as they dive,鈥� says Ura.
Next, he plans to create a version of the sub geared for surveying underwater volcanoes. The system for tracking whales and tuna will be presented at an international sea mammal symposium in Vancouver in November.
