OSLO, NORWAY - Anglers have long defended their sport by claiming that fish are incapable of feeling pain. But new research indicates that they do.
While fish have long been known to react to a jab or blow, many experts have suggested that this is simply a reflex reaction, rather than a sign of pain, despite the fact that fish have been shown to have nerve cells which activate in response to pain stimuli. One of the aspects that is thought to distinguish pain sensations from mere reflex reactions is that pain, as a conscious emotion, is remembered and recalled.
Researchers from the Norwegian School of Veterinary Science and Purdue University subjected two groups of goldfish to painful heat, by fitting them with tiny "jackets" equipped with flexible foil heaters. The heaters had an upper safety limit of 50C to prevent harm. Half the fish were given a painkilling injection of morphine beforehand, while the other half were not.
Half of the fish were given a painkilling injection of morphine beforehand, while the other half were not. Two hours later, the fish that had undergone the test without painkillers showed signs of fear and wariness such as "hovering", suggesting that they had suffered a bad experience and remembered it, say researchers.
Report co-author Dr Joseph Garner, of Purdue University, Indiana, said: "The fact that their behaviour changed so much really strongly suggests there is something going on with their memory and experience of that event that is not a reflex. I believe it does show that fish feel pain. The results show that it could not have been a simple reflex action."
The findings will add weight to calls from animal welfare organisations to ban fishing for sport.