THE BLOG
08/23/2016 12:57 pm ET Updated Dec 06, 2017

What Does A Fish Know And Feel?

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Most of us would cringe at the thought of ripping a dog's mouth open with a hook. Why don't we cringe when we think about doing this to a fish? Our society not only considers hooking and suffocating fish to be socially acceptable, we celebrate it. Fishing shows abound on TV, almost every coastal town holds fishing competitions, and CNN routinely displays photos of fishermen with their latest and largest catch. Fishing is also commonly used as a sentimental symbol of the good life.

Perhaps we don't think twice about the ways we treat fish because we don't really know much about these animals. Biologist Jonathan Balcombe wants to change this. In his New York Times best selling book, What a Fish Knows: The Inner Lives of Our Underwater Cousins, Balcombe presents the latest scientific evidence showing that there is so much more to fish than we commonly believe. And, to emphasize that fish are individuals, Balcombe doesn't use the word "fish" as a collective plural. If there is more than one fish, he uses "fishes." I had the occasion to speak with Balcombe about his book.

Why did you decide to write a book about fish and why now?

As a scientist working on animal sentience, I was often encountering new studies of fishes showing that they have rich, interesting lives. But most of this information was buried away in scholarly journals that most folks never read. Translating science into something lay-readers find engaging is something I find challenging and enjoyable. And with fishes being the most exploited group of vertebrates on Earth, there was also a strong ethical motive to write a book of popular science about fishes.

What has your research found about what a fish knows?

Fishes are incredibly diverse, and many are clearly intelligent. Consider groupers. These large, charismatic reef-dwelling fishes will approach trusted divers for handouts or just for the pleasure of being stroked. Careful studies in the Red Sea have shown that a grouper will perform a head-shaking signal to a moray eel as an invitation to go hunting together. Groupers will also point to a prey fish hiding in the reef where the grouper cannot reach but the eel can. If the prey escapes to open water, the grouper is waiting to catch it. Both species have higher hunting success when they collaborate.

Another sharp fish is the cleaner wrasse. A 2012 study showed that these small fishes learned to solve a mental problem faster than chimpanzees, orangutans, monkeys, and a scientist's four-year-old daughter.

What about what a fish feels? Do they experience emotions?

It's pretty clear that fishes can form attachments to one another, and they can become bonded to their human guardians, too. Several readers wrote to me about the games and affection they shared with individual pet fishes, and one can watch online videos of pet fishes who swim into the hand to receive gentle caresses and other pleasurable or playful interactions.

This behavior is borne out by studies like one in which wild-caught surgeon fishes responded to stress by swimming up next to a moving wand to receive caresses, which caused their stress--measured as blood cortisol--to decline. Stationary wands were ignored by these fishes, whose stress levels remained high.

Why do you think other no other scientist has written this book before?

I'm rather dumbfounded that nobody had. With all the great things we are learning about this hugely underestimated group of animals, it has to have been one of the lowest hanging fruits for an author to pick. The moment I thought of it I knew that it was something that had to be done, and it is an incredible privilege to have written this book.

What is the most interesting feedback you have received so far from a reader?

I enjoy hearing from readers wanting to share their personal stories of fishes, and I find these the most interesting. For instance, I received a letter last week from a woman in her seventies who detailed an experience from over 40 years ago when she used to feed the fishes at the back of a pet store. She had to use a stepladder to hand-feed a tank of Oscar cichlids on the top shelf. Soon these smart fishes were jumping from the water to take morsels from her fingertips. It became a game. One day, one Oscar jumped clear of the tank and made a nosedive toward the cement floor six feet below. Miraculously, a tank holding "feeder" goldfishes protruded from a shelf at floor level and the Oscar landed in it. Megan quickly returned the cichlid to his home tank. When she returned to the shop the next morning she found the same Oscar in the goldfish tank! After this happened three days in a row, she installed a lid on the Oscar tank.

You know I focus on the intersection between animal protection and human health. Why should we care about fish? Is there any benefit for us?

There are many reasons to care about fishes. For one thing, their ocean habitats produce most of the world's oxygen. For another, fishes are a critical part of aquatic ecosystems. As they go, so go their ecosystems (and vice versa). Beyond these practical considerations are the philosophical ones that recognize fishes as having lives of value to themselves. Most of us do not need to harm fishes or their habitats to live happy healthy lives. Today, consumers have many choices in what they eat, and I hope growing numbers of humans will make compassionate, conscientious food choices that no longer support industries that cause ecological harm and animal suffering.