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. At the Blue Reef Aquarium in Portsmouth, Dr Lauren Nadler from the University of Southampton introduces us to some Blue Green Chromis fish to look for clues about how and why they form their large social groups. And we explore the smelly world of fish olfaction with Professor Culum Brown from Macquarie University in Sydney Australia.

The mirror test is a classic way of trying to understand whether an animal can recognise itself or not. Professor Alex Jordan from the Max Plank institute in Konstanz, Germany explains how 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 has a fish been able to take on the test? And are there really self-aware shoals drifting through our oceans?

Producer: Emily Bird

Editor: Ben Motley

(Photo:Familiarity of the two fish. Portrait of a Hemichromis lifalili. Macro- Credit: kozorog via Getty Images)