Experiments Animal experimenters acknowledge that fish feel pain and stress. Adequate levels of analgesia reduce apprehension and stress, and decrease or suppress the perception of painful stimuli. There is very strong scientific evidence to show that they do. Fish have nerve endings near the skin which are very similar to those of humans and other mammals. The lips and mouth of fish are particularly well supplied with nerve endings.
Fish produce the same pain-transmitting chemicals as humans.
There are two main chemicals involved. When a nerve ending is damaged, a substance called bradykinin is released. This causes the nerve cell to fire, sending an electrical impulse along the nerve. When bradykinin is released near the skin, a second chemical, called substance P, is released near the spinal cord. Both substances are known to be involved in transmitting pain.