London: Scientists have discovered that fish do not feel pain as they do not have a brain system or enough sensory receptors in the nerve cells to experience suffering.
Fish do not even suffer when they are hooked and fighting for their lives, according to research by an international team.
While fish may struggle to get free, scientists say this does not mean they are in pain. Instead, they show "little effect" from injuries and toxins that would leave humans in agony.
In their experiments, researchers inserted needles into the jaws of rainbow trout.
"In spite of large injections of acid or bee venom, that would cause severe pain to a human, the trout showed remarkably little effect," Jim Rose, professor of zoology and physiology at the University of Wisconsin, who led the project, said.
Fish also resumed normal activity within minutes of surgical procedures, as well as after being caught and released back into the water.
"It is highly improbable that fish can experience pain," Rose said.
"We are not diminishing the importance of welfare considerations for fish, but we do reject the view that mental welfare is a legitimate concern," Rose added.
However, some believe while fish may not scream out, they still react to painful stimuli.
"Fish don`t scream in pain but they exhibit other pronounced reactions to painful stimuli. To claim otherwise is as sound as arguing the Earth is flat," Ben Williamson, spokesman for People for the Ethical Treatment of Animals, said.
The study was published in the journal Fish and Fisheries.