Australasian Science: Australia's authority on science since 1938

Fish Don’t Feel Pain Like Us

Fish recoil from pain but the fish pain reflex mechanism operates quite differently to the way it works in humans, according to a review in The Biology & Philosophy Journal.

“Fish don’t have complex brain structures,” said Prof Brian Key of The University of Queensland. “They do not have ‘grey matter’, the thin outer layer of brain cells that enables humans and other mammals to carry out functions such as reasoning or imagining.” Even so, Key says that fish can learn to avoid painful experiences “even when most of the brain is removed”.

Key has drawn analogies between fish and the pain processes in people with damaged grey matter and people in comas or semi-conscious states. “We suspect that some humans who have suffered strokes that damage their grey matter cannot feel pain,” he said. “This would indicate that fish – with no grey matter – also do not feel pain.”

But can’t we all see that a fish caught on a hook is in pain? “When a fish is flapping about on the deck of a boat, humans respond emotionally,” Key said. “It’s an anthropomorphic response – we are mentally transposing the human experience – presuming that the fish has the same emotions and feelings as a human. However, the fact that a fish will continue to struggle with a hook in its mouth would indicate it doesn’t feel pain in the same way that we do.”

Key said although it was unlikely that fish could feel pain, harmful stimuli still caused stress to their bodies. “Fish secrete stress hormones,” he said. “This research should not be interpreted as meaning that we do not need to care for their welfare.”