Project Description

Cover for the book What a Fish Knows. Features a fish looking forward in an underwater scene.

What a Fish Knows

Author: Jonathan Balcombe · Subject: Animal Rights


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.

The reef-dwelling damselfish identifies its brethren by face patterns visible only in ultraviolet light, and some species communicate among themselves in murky waters using electric signals. Highlighting these breakthrough discoveries and others from his own encounters with fish, Balcombe inspires a more enlightened appraisal of marine life.

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.

About the Author

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.


“A Must Read Book” – The Sunday Times (London) 

“One of the Best Books of the Year” – National Post

“Latest Reads to Pique Your Curiosity” – The Toronto Star

“Numerous books have shown me how utterly ignorant I am about most creatures I share this planet with, but none humbled me more than What a Fish Knows by Jonathan Balcombe.” – Cornelia Funke, The Observer

“We Buddhists consider all animals, including fish, as sentient beings who have feelings of joy and pain just as we humans do. We also believe that they have all been kind to us as our mothers many times in the past, and are deserving of our compassion. Therefore, we try to help them in whatever way we can and at least avoid doing them harm. In What A Fish Knows, Jonathan Balcombe vividly shows that fish have feelings and deserve consideration and protection like other sentient beings. I hope reading it will help people become more aware of the benefits of vegetarianism and the need to treat animals with respect.” – The Dalai Lama

“An extended exploration of the world from a piscine perspective . . . Balcombe makes a persuasive case that what fish know is quite a lot.” – Elizabeth Kolbert, The New York Review of Books

“[An] exhaustively researched and elegantly written argument for the moral claims of ichthyofauna.” – Nathan Heller, The New Yorker

What a Fish Knows will leave you humbled, thrilled, and floored. Jonathan Balcombe delivers a revelation on every page, presenting jaw-dropping studies and stories that should reshape our understanding of, and compassion for, some of the most diverse and successful animals who have ever lived. After reading this, you will never be able to deny that fishes love their lives as we love ours, and that they, too, are vividly emotional, intelligent, and conscious. Bravo!” – Sy Montgomery, author of The Soul of an Octopus, a National Book Award finalist

“Balcombe builds a persuasive argument. Writing in a straightforward, somewhat breezy style, he makes his case partly through a compendium of fascinating anecdotes and scientific findings that illustrate the complexity and creativity of fish behavior . . . Dozens of startling revelations emerge.” – Alan de Queiroz, The Wall Street Journal 


Cover for the book What a Fish Knows. Features a fish looking forward in an underwater scene.

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