Your article (Farmed fish suffer pain and stress, says report that criticises welfare failings, 2 April) states that fish “contrary to previously common beliefs – feel pain”. This is misleading. To survive, all animals must be able to detect and escape from anything that might eat or damage them. This is why they all have sensory systems to detect anything noxious or dangerous.
Pain is a conscious sensation experienced by humans. We know other humans feel pain because we can can communicate with each other. We can only guess that other mammals, birds and possibly also reptiles with large, complex brains like ours will also experience pain.
The claims made about fish – and invertebrates like insects, lobsters, and snails – feeling pain are based on experiments that show they can detect and learn about noxious stimuli. Many also show a release of hormones which raise alertness and help in escape. But showing that they detect and have a hormonal response to noxious stimuli does not mean they are conscious and feel pain. However, we should still campaign for improved welfare conditions for all seafood animals.
Emeritus professor of zoology, University of Bristol