2 . “The mosquitofish is one of the 100 world’s worst invasive (侵入的) species, and present methods to kill it are too expensive. It will take too much time to successfully control the spread of the mosquitofish,” says Giovanni Polverino. “This global pest is a serious threat to many animals living in water. Instead of killing them one by one, we’re presenting an approach that can inform better strategies to control this global pest. We made their worst nightmare become real: a robot that scares the mosquitofish but not the other animals around it.”

In the presence of the robotic fish, mosquitofish would stay closer to each other and spend more time at the center of the testing area. They were unwilling to swim to unknown waters. They also swam more crazily, with frequent and sharp turns, than those who haven’t met the robot. They swam away from the robot and back to their living area. The influence of fear lasted. The scared fish were less active, ate more, and froze longer, presenting signs of anxiety that continued weeks after their last encounter (相遇) with the robot.

For the tadpoles (蝌蚪) the mosquitofish usually hunt for food, the robot’s presence was a change for the better. Tadpoles have poor eyesight. They don’t see the robot well. Because the robot changed the behavior of the mosquitofish, the tadpoles didn’t have predators (捕食者) at their tails anymore and they were more willing to explore in the testing area. “It turned out to be a positive thing for tadpoles. Once freed from the danger of having mosquitofish around, they were not scared anymore. They’re happy.”

After five weeks of brief encounters between the mosquitofish and the robot, the team found that the fish spent more energy towards escaping than reproducing. Male fish’s bodies became thin.

“While successful at preventing mosquitofish, the lab-grown robotic fish is not ready to be put into the wild,” says Maurizio Porfiri. The team will still have to overcome technical challenges.