Fish do not feel pain as they lack a brain or enough sensory receptors to experience suffering. Fish also do not suffer when they are hooked and are fighting for life, say scientists. While they may struggle to become free, it does not imply that they are in pain. Instead, they are little affected by injuries and toxins that would leave us in agony.
The researchers inserted needles into the jaws of rainbow trout. Despite large injections of acid or bee venom, which would bring severe pain to a human, the fish showed a minimal effect, says the University of Wisconsin team. They also resume normal activity within minutes of surgery, and after being caught and put back into water.