Underwater Robot Fish Influence Golden Shiner Swimming Behavior

Robots are gaining steam in the world of biology. They're showing researchers exactly how they can influence species to perform different behaviors. Now, scientists have discovered that a robotic fish can be used to understand and influence the complex swimming behaviors of schooling fish.

In order to look at schooling fish a bit more closely, the scientists designed an experiment to examine the interplay and visual cues and flow cues--changes in the water current as a result of tail-beat frequency--in triggering a live golden shiner fish to either approach or ignore a robotic fish. The researchers created two robotic fish that were similar to a live golden shiner in aspect ratio, size, shape and locomotion pattern. However, one was painted with the natural colors of the shiner while the other was painted in different colors. Then, the scientists placed each robot to the inside of a water tunnel and introduced a live fish.

"When the fish first encountered a robot that mimicked both the coloration and mean tail-beat frequency for the species, it was likeliest to spend the most time in the nearest proximity to it," said Maurizio Porfiri, one of the researchers, in a news release. "The more closely the robot came to approximating a fellow golden shiner, the likelier the fish was to treat it like one, including swimming at the same depth behind the robot, which yields a hydrodynamic advantage."

The researchers found that flow cues created by tail-beat frequency were a critical trigger for shoaling behavior. Coloration, though, played a larger role. The shiners were always drawn more to the naturally colored robot.

"Even at tail-beat frequencies that were less than optimal for the live fish, the shiners were always more drawn to the naturally colored robot," said Porfiri in a news release.

The findings reveal that it's not just flow cues that fish respond to. Instead, live fish react to a combination of flow and visual cues. This, in turn, allows researchers to better understand how biological organisms react to one another. By using robots, scientists can learn more about the world we live in. In addition, these machines could be potentially used as a means to protect marine wildlife, including birds and fish, in the wake of environmental hazard.

The findings are published in the journal PLOS One.