Fishing for pain and emotion

To many , the notion that we should care about the suffering of fish seems absurd. For most, fish amount to little more than swimming protein, a healthy food to be plucked from rivers and seas. But, as a disturbing new book, Do Fish Feel Pain? shows scientists are now confident that fish do not only feel pain, but have a complex emotional life, too.

Author Victoria Braithwaite's conclusion is surprising, because we are not used to thinking about fish as sentient at all.

The first question is whether fish are equipped with the senses that would enable them to feel pain?

The poison test

The author herself has conducted experiments on fish to test this out. Using two chemicals — bee venom and vinegar — Dr Braithwaite has shown that fish which have been injected with these "painful" stimulants around the mouth rub the affected area and lose interest in food until the poison had worn off.

Can fish suffer? Well, recent experiments by Dr Peter Laming, a marine biologist in Belfast, showed that a fully developed pain "pathway" is present in goldfish, linking receptors in the skin, via the spinal cord, to the brain.

Passing the IQ test

Our understanding of animal intelligence is changing all the time. Elephants, apes and dolphins, for example, have been shown to recognise themselves in mirrors — which requires more intelligence than it sounds. But what of fish? Well, scientists in Madrid have discovered that goldfish have the ability to learn and remember their way around mazes.

This ability — to create a mental ranking — is called transitive inference, and humans cannot do it until they are 4 years old.

Perhaps the most convincing evidence that fish have "minds" comes from studies of two reef species: the grouper and the moray eel. Swiss scientists have found that these predators cooperate in catching prey.

What is extraordinary about this is that, aside from humans, who hunt with dogs, this is just about the only example of two separate species cooperating in a hunt.

So, more and more scientists — there are still sceptics — believe fish can feel pain. Furthermore, they demonstrate intelligence and self-awareness.