Various researchers have since made similar discoveries. In 2006, Rebecca Dunlop, Sarah Millsopp, and Peter Laming, researchers from the Queen’s University in Belfast, Northern Ireland, published a study demonstrating that fish can also learn to avoid painful experiences. They gave eight goldfish an electric shock. All of them darted away, but more surprisingly, the fish didn’t immediately return to the area where the incident took place—even when food was present. The scientists concluded that the response to the initial shock might have been instinctual, but the decision to stay away indicated more complex pain responses.
Looks can be deceiving. Though they appear alien, fish share some important anatomical similarities with mammals, who have long been thought to experience pain. In response to noxious stimuli, fish bodies produce the same opioids (like natural painkillers) that are present across the animal kingdom. And when they’re injured, parts of the brain considered essential for conscious sensory perception light up like glow sticks at a rave, just as they do in terrestrial animals.
Sneddon says the biological function of pain is virtually universal to the living creatures that experience it. “It’s an alarm system to warn you about injury,” she says. “If it was not a horrible psychological experience, animals would not learn to avoid painful stimuli and would just go about their lives hurting themselves continually.”
Others argue that fish aren’t capable of experiencing pain, and that any recorded behavioral responses are more likely unconscious reactions to negative stimuli. In other words, they believe fish can instinctually detect harm to their bodies, without any suffering.
James Rose, an avid angler and professor emeritus of zoology at the University of Wyoming, has claimed fish don’t possess a human-like capacity for pain because our nociceptors—neural cells that transmit pain reflexively—are different. Those in fish, he and his peers wrote in a 2012 paper, more likely trigger instinctual escape responses than signal injury.
Two years later, BBC Newsnight interviewed Bertie Armstrong, head of the Scottish Fishermen’s Federation. He argued that scientists haven’t adequately proven that fish feel pain, and said that marine animals shouldn’t have the same welfare protections as those grown on land. Alternative slaughter methods, Armstrong said, could be cost prohibitive for the fishing industry.
Then, in 2016, Brian Key, a biomedical scientist from Australia’s University of Queensland, argued that fish lack the neurological architecture to feel pain. The squishy neocortex that sits atop a human brain is like a city: Various neighborhoods, connected by neural highways, work together to produce vivid experiences of pain. The crux of Key’s argument is that, because fish brains lack that same organized neocortex, they aren’t able to consciously experience hurt as we do.
Droege and colleagues have countered Rose’s argument. They’ve found homologous structures in fish that may play the same role as elements of the human brain—arguing that our own pain, in fact, tells us very little about that of animals.
On the BBC program, the late Pennsylvania State University biologist Victoria Braithwaite (who wrote the 2010 book, Do Fish Feel Pain?) countered Armstrong, saying that fish undeniably don’t have the same pain response as humans, but that they likely feel it similar to other land animals: If “we extend birds and mammals welfare, then logically, why not fish?” She went on to argue that the protection of fish doesn’t have to be mutually exclusive with viable commercial fishing outcomes—there are probably some innovations that could be made to decrease suffering.