Fish Can Recognize Themselves in Photos, Study Finds

A fish staring at its own reflection
An angelfish staring at its own reflection. Stock photo.

A new study has found that blue streak cleaner fish are capable of recognizing their own reflection in photos.

The fish passed the mirror test and were able to distinguish their own faces and images of other fish in photographs.

Researchers from Osaka Metropolitan University in Japan and the University of Neuch√Ętel in Switzerland published a study in which they demonstrated how the fish identify themselves.

The Self-Recognition Fish Experiment

The scientists presented the fish with four different photos: A photo of themselves, a photo of another fish, a photo of their head composited onto the body of another fish, and a photo of their body with a different’s fish’s head composited on.

The fish were recorded acting aggressively toward photographs of an unknown individual but were not combative toward their own picture.

They also displayed “limited aggression” toward the composite photos. In fact, the scientists noted that they were less aggressive toward the composite photos that featured their own heads while acting more fierce toward the composites with their own bodies.

“Together, these results demonstrate that cleaner fish can recognize themselves in a motionless image and appear to achieve this by self-face recognition,” write the scientists in their paper.

The aggressive behavior consists of rushing toward the photo, bumping with the body, and biting.

neon goby
A neon goby cleaner fish | Franklin Samir Dattein

The scientists did another test where they presented yet more self-photographs to the fish, but this time they put a brown color mark on the throat.

“We speculated that if cleaner fish recognize the self-photograph as the self, marked self-photographs would also elicit throat-scraping behavior,” the scientist writes.

Eight fish were presented with these manipulated photos, and six of them displayed throat-scraping behavior.

In contrast, none of the fish were observed scraping their throat when observing a non-manipulated photo of themselves or when observing a photo of another fish that had a marked throat.

“We consider this photograph mark test…provides compelling evidence that cleaner fish recognize self-photographs as the self,” the scientists write.

Last month, a similar study showed penguins also displaying signs of self-awareness.

Image credits: Header photo licensed via Depositphotos.