Museums and aquaria could soon be displaying lifelike robotic models of marine creatures-some of them long extinct-thanks to the efforts of engineers at Mitsubishi Heavy Industries in Japan. The company has just developed a remote-controlled sea bream that looks and swims just like the real thing. And since you don't need to feed the 60-centimetre-long fish or clean out its tank, it makes an ideal exhibit.

The robotic sea bream is controlled via a desktop computer. This controls movement of the tail fin and two pectoral fins. "It wasn't possible to replicate the exact method of propulsion used by the sea bream," says Mitsubishi robotics engineer Yuuji Terada. "So we're using an elastic oscillating fin that we first developed for use in our underwater vehicles." The battery-powered fins oscillate at between 0�2 and 1 hertz, and will propel the robot at up to 0�25 metres per second. The battery is automatically recharged by a coil inside the fish that draws power from an electromagnetic field that permeates the fish tank.

After spending four years getting the bream to swim accurately, Mitsubishi says its next step will be to build a robotic replica of a coelacanth-the "fossil fish" that was once thought to be extinct. After that it plans to bring back several extinct fish from the pre-Cambrian era.

Author: Peter Hadfield, Tokyo
New Scientist magazine issue 29th May 1999

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