One of us! Engineers fool fish school into accepting robotic koi

One fish, swimming alone, encountering a robotic fish impersonator will be wary and tend to avoid the robot, but a group of real fish are more likely to accept the robot as one of their own, and sometimes even abandon other real fish to follow the robot.

Those are the findings of engineers from Peking University and China Agricultural University who created a realistic koi fish robot, and placed one or two in a tank with real fish to see how they would respond. 

The research published in Bioinspiration and Biomimetics, was designed to gain insights into how real fish interact with fish-like robots.

The researchers went to great lengths to create a realistic 25cm long black fish-like robot, designed to mimic a koi – an ornamental freshwater fish – in shape, colour and behaviour.

The authors say fish have highly evolved acoustic sense organs, which allows them to perceive not only the differences in shape and movement patterns of biomimetic robots but also the acoustic noise generated by the vibration of the motor and the friction of their mechanical structure.

The design of the robot – a self-propelled koi-mimicking robotic fish entity – incorporated sensors and a fish-like swimming strategy, enabling the robotic fish to interact naturally and efficiently with the fish school.

“Fish do not always swim continuously, but instead have a sliding phase after a series of undulations during which they can observe their surroundings, regain energy, and prepare for the next action,” the paper notes.

The swimming energy of the robot had a significant impact on how real fish responded to the robot.

Real fish were more attracted to the robot mimic when it swam at high frequency and low speed (with smaller swing).