Despite all the bad press that goldfish get about their memories, fish have feelings, too, And according to Jonathan Balcombe, they've been getting badly misunderstood for ages.
He studies animal behaviour but doesn't just want to observe this from the outside. In two previous books, Pleasurable Kingdom and Second Nature, he tries to get inside animals' heads to understand their thoughts, motivations and feelings.
In his latest book What a Fish Knows, Balcombe examines the inner lives of fish.
As well as having lifelong relationships and intricate dating rituals they can also use tools, hunt in tandem and punish wrongdoers... and recognise individual people from the fishbowl!