Small robots could help look after salmon without stressing them out

Salmon seem to prefer small robots to larger ones, which could help guide how we automate fish farms. Monitoring of commercial fish farms is normally done by a human diver, but that can be disruptive for the animals, so Maarja Kruusmaa at the Norwegian University of Science and Technology and her colleagues wanted to see if a robot could do the job without unsettling the fish as much. The researchers conducted 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 uses flippers to swim. They used the footage to measure how close the salmon got to the diver or robots and how fast they beat their tails, indicators of how much the fish were disrupted.