UK biologists have infiltrated underwater society with a computer-controlled fish that recruits and leads other fish in a school.
Dubbed 'Robofish', the device is a plaster cast of a three-spined stickleback fish that is mounted on a rare-earth magnet.
It is controlled by an electromagnet that is located beneath the tank and controlled, in turn, by TestPoint and Microsoft Excel software packages on a PC.
Because the researchers aimed to study how the behaviour of individual fish might influence the movement of others, they had to convince the sticklebacks that Robofish was one of their own.
"The main challenge was to convince the fish that the robotic fish was in fact a real fish," lead researcher Jolyon Faria told iTnews.
"We paid careful attention to body shape and colouration for this purpose," said Faria, a PhD researcher at the University of Leeds.
"The robotic fish is programmed to move around the tank at a speed, and in a manner, that convinces the three-spined sticklebacks that the robotic fish is in fact a real fish."
Faria and his colleagues studied two types of interaction between the sticklebacks and Robofish: recruitment of fish from a refuge; and initiation of a new swimming direction to test leadership.
They placed Robofish in a tank with live fish collected from the Great Eau river estuary in the UK and observed their response to Robofish leaving its refuge, and making a 90-degree turn shortly after.
Robofish's behaviour was found to quickly coax out single fish that would normally hesitate to venture out of the refuge in an unfamiliar tank.
The robotic fish was also able to cause fish in groups of up to ten to turn in the same direction as itself, although its influence diminished after the first 30 minutes the fish had spent in the new tank.
While Faria highlighted "some highly impressive" robot fish produced at the University of Essex and the University of Washington, he said Robofish was the first to "interact convincingly" with a school of fish and convince the whole group to make a sharp turn.
The researchers concluded that robots had great potential in fish behaviour research, which could contribute to a more general understanding of collective animal behaviour.