Fish feel pain

For centuries it was thought animals such as dogs or horses didn't feel pain, which now seems contrary to common sense.

Now people are finally beginning to realise that slamming a barbed hook in a fish's mouth and letting him asphyxiate on land also causes intense suffering.

Nociceptors are nerve cell endings found throughout the human body, in other animals, and on the skin of fish, that initiate the sensation of pain. Researchers from the University of Edinburgh have researched the presence of these nerves and tested the behaviours of fish responding to painful stimuli.

"We found 58 receptors located on the face and head of the rainbow trout," said Senior Lecturer, Dr Lynne Sneddon. "The 18 ‘polymodal nociceptors', which responded to all potentially painful stimuli in the trout, were the first to be found in fish and had similar properties to those in humans".

Their experiments found that fish learn to avoid unpleasant stimuli such as electric shocks, and the piercing of their lips by sharp hooks. The research demonstrated that the fishes' behaviour was adversely affected by a potentially painful experience, and that these behavioural changes were not simple reflex responses.