Think you know what a fish knows? Think again.

In my earlier post, Fish Are Important Too, I recalled how I attended a meeting of the Council of Europe in Strasbourg and visited some fish farms. What I saw has stayed with me ever since. Not just the sight of large numbers of fish in obvious distress, but also the lack of concern from officials and veterinarians.

I promised there and then that I would do more to bring the suffering of farmed fish to light.

Here at Compassion, we’ve been vocal lobbyists for a better deal for farmed fish and have published a number of heavy-weight reports over the last 25 years.

I was therefore hugely excited to read What a Fish Knows by Jonathan Balcombe, and even more excited to interview him. As director of animal sentience at the Humane Society Institute for Science and Policy and the author of four books on animal sentience, he wants his new book to “give voice to fish in a way that hasn’t been possible in the past.”

I asked him to tell me more.

Jonathan: Fishes badly need our attention. We catch and eat more of them—over a trillion a year by some estimates—than any other kind of animals, and the methods used to kill them are cruel and unforgiving.

When the idea of writing a book about the inner lives of fishes came to me five years ago, I almost fell out of my chair because I realized immediately that there was such an obvious need.

There are, of course, many books on fishes, but almost all are about how to catch or cook them. Of those written about fish biology, only a handful have advocated directly for fishes, and I credit the contributions of Victoria Braithwaite and especially Robert Wintner there.

As a scientist I was aware of some exciting discoveries about how fishes perceive, think, feel, and socialize, but also that so little of it was percolating up to the public consciousness.

By showing that fishes have rich, complex lives, What a Fish Knows aims to change our views on these misunderstood animals. Quite aside from their beauty and their interest in not being harmed, fishes and their habitats are critical components of the biosphere; where they go, so go us.

Philip: How do you respond to someone who disagrees with you when you say fish feel pain and they think?

Jonathan: Even without scientific backing, the notion that fishes cannot feel pain has always struck me as absurd. Fishes are full members of the vertebrate clan, with backbones, nervous systems and sensory capabilities that often exceed our own. Fishes behave flexibly and they are socially sophisticated. They show preferences, plan, use tools, deceive, help others, and keep accounts. Fishes can learn by watching others, and change their behavior according to who is watching them. Contrary to popular myth, they can remember past events months or years later. They can even recognize us by our faces.

Fishes clearly respond to pain (and to pleasure).

Careful experiments with anesthetized trout have shown that bony fishes have different types of pain receptors for heat, chemical, and mechanical pain, and that their behavior is adversely affected by exposure to a presumptively painful event (injection of acid).

When zebrafishes were kept in a two-chambered tank, they preferred a dimly-lit chamber furnished with plants and rocks for cover. The adjoining chamber—barren and brightly lit—was avoided completely. When the fishes were injected either with acid or a benign saline solution, all remained in the enriched part of the tank. Then, when a painkiller was dissolved in the barren chamber, the acid-injected fishes began to leave their preferred quarters and started swimming in the normally less-preferred, barren chamber. This is a very convincing demonstration that those fishes were feeling pain, and that they had the wherewithal to seek relief.

Philip: Is it possible to intensively raise fish in tanks, like chickens in cages, and not harm their welfare?

Jonathan: No. Intensive confinement is universally stressful for animals.

All sentient creatures need space to carry out their natural behaviors, and they become distressed if this need is constantly frustrated.

Fish farms multiply stress for fishes. In addition to lack of space, farmed fishes often must endure rampant infestations from sea lice and other parasites that flourish in the crowded conditions. Larger fishes may show aggression towards smaller, subordinate ones, who in turn have nowhere to escape. Pesticides, antibiotics and other chemicals add another layer of stress. Then there is the boredom of swimming in endless circles; fishes are superb navigators so they must be aware that they are making no forward progress.

Norwegian researchers recently studied young farmed salmon and concluded that many are severely depressed. Stunted and only a third the weight of their comrades, the depressed salmon stopped eating, grew listless and eventually floated to the surface and died. The scientists found higher levels of cortisol (a stress hormone) in their bodies. They concluded that these so-called “drop-outs” were unable to cope with the chronic effects of overcrowding and inescapable aggression from other fishes.

Philip: You quote various studies which show fish populations halved between 1970 and 2012. Some heavily fished species, including tuna and mackerel, fell by almost 75 percent. Is there going to be a day when there are no fish left in the sea?

Jonathan: If that day ever comes, humans probably won’t be around to witness it. For one thing, the oceans produce more than half of the world’s oxygen. Furthermore, without the presence of fishes in the food chain, the entire global ecosystem would collapse. The loss of some half of all marine life is a warning that we cannot continue on our current path.

I also want to encourage the public to embrace a broader ethic in our evolving relationship to fishes.

Beyond the impact on us, continued loss of fish life represents a loss of so much that makes the living world so beautiful and rich. Now that we have the technology to observe their lives under the sea, we can witness a stunning realm that before 1950 was largely hidden from our view. The sleek beauty of sharks, the phantasmagoria of reef colors, the graceful undulations of rays, and the mesmerizing coordination of giant schools that can make them resemble a single giant organism—they were invented long before our kind existed, and they remind us that it isn’t all about us.

If we want a future worth living in, then we owe it to them, and to ourselves, to respect, protect and preserve our underwater cousins.

Philip: Thank you!