Are we wrong to assume fish can't feel pain?

The impression that fish are insensate, short of memory and, therefore, can be caught, killed and eaten without guilt, is being revisited. Angling, the so-called “gentle art”, derives enjoyment from the struggles of its quarry. Up to 2.7tn wild fish are caught worldwide every year; a third of which are ground into feed for chickens, pigs and other fish. The ethics of all this depend on what fish do or do not experience. It is a question dividing the science community; forced to reassess in light of new evidence.

Their battle rages. In 2016, the journal Animal Sentience published Australian neuroscientist Brian Key’s essay Why Fish Do Not Feel Pain. Key had earlier written that “it doesn’t feel like anything to be a fish”. Now he argued thus: mammals feel things, and only mammal brains have a structure called the neocortex; ergo fish, lacking a neocortex, feel nothing.

But that is like saying that because we travel using legs, then fish, who have no legs, cannot travel. Key’s essay triggered more than three dozen opposing scientific responses, pressing new evidence that fish are aware; of pain, of anxiety, of pleasures.