There are more than thirty thousand species of fish–more than all mammals, birds, reptiles, and amphibians combined. But for all their breathtaking diversity and beauty, we rarely consider how fish think, feel, and behave.

In What a Fish Knows, the ethologist Jonathan Balcombe takes us under the sea and to the other side of the aquarium glass to reveal what fishes can do, how they do it, and why. Introducing the latest revelations in animal behavior and biology, Balcombe upends our assumptions about fish, exposing them not as unfeeling, dead-eyed creatures but as sentient, aware, social–even Machiavellian. They conduct elaborate courtship rituals and develop lifelong bonds with shoal-mates. They also plan, hunt cooperatively, use tools, punish wrongdoers, curry favor, and deceive one another. Fish possess sophisticated senses that rival our own.

An illuminating journey into the world of underwater science, What a Fish Knows will forever change your view of our aquatic cousins–your pet goldfish included.

Jonathan Balcombe is the director of animal sentience at the Humane Society Institute for Science and Policy and the author of four books, including Second Nature and Pleasurable Kingdom.

A popular radio guest, he has also appeared on the National Geographic Channel and in several documentaries, and he is a frequent contributor of features and opinions to The New York Times, The Washington Post, The Wall Street Journal, Nature, and more.