Fish do not feel pain, as they lack the necessary brain system and sensory receptors to experience it, suggests a new study.

A team of researchers led by James Rose from the University of Wyoming has revealed that the reaction of a fish when it gets hooked is just an unconscious reaction, and not a response to pain.

Earlier studies have shown that fish have "nociceptors" - sensory receptors which are found in humans and which send signals to the brain to allow them to feel pain as a response to damaging stimuli. But the new research team has found that the sensory receptors in fish are not enough to experience pain, reports The Telegraph newspaper.

Instead, the reaction let out by the fish when they get hooked or fight for their lives is just an unconscious reaction. According to Rose, fish species like trout do not have a developed neocortex, required to feel pain.

For the study, the research team caught a rainbow trout with a hook and then released it back in the waters. They found that the fish resumed normal activity immediately after it was released. It also survived for longer periods, suggesting that the trout did not feel any pain.

For years, there have been debates between anglers and animal rights activists whether fish are impervious to pain or not. A number of studies have suggested that fish can experience pain. For example, a study carried out by researchers from University of Edinburgh showed that fish responded to damaging stimuli.

The research team from the University of Edinburgh injected the rainbow trout with an acid solution in their lips. They noticed behavioral and physiological changes in the trout as seen in other higher mammals. This made them conclude that fish feel pain.

However, the new research team from the University of Wyoming revealed that only a small number of "C fibres" (a type of nociceptor responsible for pain) were found in fish. They concluded that the fish might display instinctive responses, but they do not feel any conscious pain, according to The Telegraph report.

The findings of the study appear in the journal Fish and Fisheries.