Salmon appears to incline toward tiny robots to bigger ones, which could help manage how everyone automates fish farms.

Monitoring of commercial fish farms is normally done by a human diver, yet that can be disruptive for the animals, so Maarja Kruusmaa at the Norwegian University of Science and Technology and her associates wanted to check whether a robot could carry out the responsibility without agitating the fish to such an extent.

The scientists led a test in a sea cage in Norway containing 188,000 salmon. They filmed the salmon using a diver, a commercial underwater robot called the Argus Mini that propels itself with thrusters, and a smaller underwater robot called U-CAT, which utilizes flippers to swim.

They used the footage to measure how close the salmon got to the diver or robots and how quickly they beat their tails, indicators of how much the fish were disturbed. The salmon drew nearer to U-CAT than the Argus Mini or the diver, and beat their tails slower around the small robot – just somewhat quicker than when there was no disruption at all. This was genuine whether or not the interruption was moving, how it was moved, the sound is created or it’s color.

“Size matters,” says Kruusmaa. Indeed, it is by all accounts the only thing that issues fundamentally to how the fish respond to an interloper. “You can make a very complicated robot that’s extremely quiet and has a smiley face and speaks a fish language, but that would be hugely costly and the fish don’t seem to care.”

This is significant, not as a result of moral considerations of whether the fish everyone eats lead good lives, yet also because other work has demonstrated that better welfare leads promptly a better return, Kruusmaa says. “The happier the fish are, the healthier the fish are, the better they eat, the better they grow, the fewer parasites they have and the less they get sick.”