Scientists from three different European countries – Norway, Belgium and the UK – are now launching a new research project where the aim is to find out if cods can feel pain or not.

“Most people agree that mammals and birds can feel pain, but people are less sure about fish,” says project leader Øyvind Aas-Hansen of NOFIMA, an aquaculture research institute whose headquarters are in Tromsø, Norway.

Fish show many signs of being able to experience pain, but we still know very little about how their brains react to stimuli that would cause mammals and birds to feel pain. According to some scientists, the brain of a fish is not equipped with certain structures needed to process pain, but others believe that fish nevertheless do sense some type of pain.

What we do know is that fish show a long row of behavioural responses that could be interpreted as signs of pain, such as avoidance reactions. Fish are also capable of producing pain-relieving opiates and the fish brain is equipped with receptors for both pain and opiates.

The European researchers hope that modern medical technology, especially functional magnetic resonance imaging (fMRI) and electroencephalograms (EEGs) will make it possible for them to learn more about how the cod brain actually works. The aim of the study is to indentify which parts of the cod brain that becomes activated when a cod is exposed to potentially painful stimuli, and the researchers will also study how these signals are processed.

In order to test the brain of a fish, there is no need to expose it to any type of severe or prolonged pain; a mild stimulus that simply provokes an unpleasant sensation is enough to see how the brain reacts. “We will use the same procedures as those used on healthy human volunteers,” Dr Aas-Hansen explains.

If cods are indeed able to feel pain, Dr Aas-Hansen hopes that the results of the study will be used as yet another argument in favour of keeping aquarium fish in benevolent conditions. The study is however unlikely to affect European legislation since most regulations already assume that fish can feel pain.

Dr Aas-Hansen also points out how comparative research on how the brain works in different animals can give an insight into our own human brain. “This is ground-breaking work,” he says. “No other scientists have previously studied the cod’aquarius brain this way.”

The project will run for three years and is funded by the Norwegian Research Council.