Do fish know what they look like?

There’s something fishy going on in the Czech Republic, where CrowdScience listener Ian lives. He keeps tropical fish, and he’s noticed that when he adds new ones to his tank, they swim with others of the same breed. He wants to know how they recognise each other. Do they know what they look like, and recognise others that look the same, or is there something else going on?

Presenter Anand Jagatia takes a deep breath and dives into the science. Fish don’t see the same way we do, and some can even see colours in the ultraviolet spectrum. But does that really help them know their wrasse from their rainbow trout?

The mirror test is a classic way of trying to understand whether an animal can recognise itself or not. Scientists place a visible mark on an animal, show it a mirror, and if the animal tries to rub it off, it suggests that the animal knows it’s seeing itself. A variety of apes, elephants and dolphins have passed with flying colours, but they’re the exceptions rather than the rule. So are there really self-aware shoals drifting through our oceans?