The fish does not scream in pain, and its face never vibrates. It lacks the cortex through which a person experiences pain.
Long it was believed that the animals did not feel pain. They cannot experience suffering because they lack both soul and consciousness, thought the French philosopher, for example. René Descartes (1596–1650).
Today, our information should be at a completely different level. The feeling of pain in homogeneous vertebrates has no longer been denied. Until very recently, however, it has been widely assumed that fish will not hurt.