Fish recognise individual divers
This is a pretty neat discovery by Maëlan Tomasek, Katinka Soller, and Alex Jordon, from the Max Planck Institute of Animal Behaviour; Wild fish in the Mediterranean Sea can recognise individual divers.
Well, more precisely, saddled sea bream (Oblada melanura) and black sea bream (Spondyliosoma cantharus) can recognise divers by their dive gear.
Let’s step back a bit. It’s not unusual for scientific divers studying marine animal behaviour to use food as a reward in experiments. At the STARESO research station in Corsica, France, scientific divers carrying food rewards noticed that certain fish started following them around, ignoring all other divers.
Thus, an experiment was born to see if the fish really were able to tell the individual divers apart.
First, Katinka Soller put on a bright red vest and fed fish as she swam for 50 metres. After a number of dives, Katinka removed the red vest, hid the food, swam for 50 metres, then fed the fish who followed her. Twelve days later, 20 fish were regularly following Katinka.
Next, Maëlan Tomasek entered the water. Maëlan’s dive gear was a bit different from Katinka’s - like different colour fins, and different colours and patterns on the wetsuit. Both divers would start at the same point and swim off in different directions. After 50 metres, Katinka would feed the fish that followed her. Maëlan never fed the fish.
On the first day, the fish split, following both Maëlan and Katinka. Over time, more and more fish followed Katinka..
But what would happen if both divers were wearing identical dive gear? That was the final part of the experiment. The result - the fish didn’t follow Katinka, who had the food, more than Maëlan.
This, the researchers say, suggests that the fish use visual cues like colours and patterns to identify the divers.
