Do fish feel pain?

This is the first of a two-part series exploring the question, “Do fish feel conscious pain?” Part two, "Pain in fish: Weighing the evidence," appeared 30 January.

In December, fish welfare activists made the news when they picketed locations of Captain D’s and Long John Silver in Cincinnati and Dayton, Ohio, to protest the killing of fish for food.

Earlier this month, Switzerland banned the practice of boiling lobsters alive to cook them, and joined Italy in outlawing the practice of transporting lobsters on ice or in icy water, arguing that it causes unjustifiable suffering before death. And a couple of months ago, National Public Radio ran a story on whether people should care if their fish dinner was treated humanely.

Acknowledging public concern, the American Veterinary Medical Association's 2013 Guidelines for the Euthanasia of Animals states: “Compelling recent evidence indicates finfish possess the components of nociceptive processing systems [systems for perceiving painful or injurious stimulus] similar to those found in terrestrial vertebrates, though debate continues based on questions of the impact of quantitative differences...in major nerve bundles.”

At the crux of the debate, which has profound implications for the seafood industry, is the question, “Do fish feel conscious pain?” Concern over the issue has already led to increasing regulation of human conduct toward fish, particularly in Europe, where governments have taken steps to reduce alleged fish pain and suffering.

Although scientific research into the issue has been taking place for more than two decades, there is still no consensus one way or the other. Two recent publications, one championing the belief that fish feel conscious pain and the other asserting they do not, were released in 2016 and 2012, respectively. The authors of both publications take a deep dive into the extant published academic research on the subject, but come to opposite conclusions, alternately supporting and debunking the idea of fish consciousness and their ability to feel pain.

The New York Times 2016 Bestseller by ethologist Jonathan Balcombe, entitled “What a Fish Knows: The Inner Lives of Our Underwater Cousins” presents an array of fish studies conducted by scientists who concluded that fish are conscious and do feel pain the way that humans do. The book will soon be available in 12 languages other than English.

On the other hand, the 2012 study by seven research scientists, with University of Wyoming Professor Emeritus James D. Rose as lead author, reviews and analyzes much of this same fish research and arrives at the opposite conclusion, that “much of this research seems mission-oriented and differs, accordingly, from the more detached tradition expected of basic science.”  They further state: “One of the most conspicuous shortcomings in discussions of scientific evidence for fish pain has been the selective consideration of evidence.”

Balcombe told SeafoodSource, in email and telephone interviews, that in his opinion, “Fishes are clearly sentient…They have the capacity to feel things from conscious pain to pleasure and their behavior, social lives, and their biology show that they have many ways to experience their lives through emotions and intelligence.”

Balcombe has a master's degree in biology and a Ph.D. in ethology and has been a vegan for more than 20 years.

Among the research presented by Balcombe is a study by Lynne Sneddon, the director of bioveterinary science at the University of Liverpool (U.K.), who investigated whether fish sought out relief from inflicted pain.

“Like most captive animals, fishes like stimulation,” Balcombe said. “For instance, zebrafishes prefer to swim in an enriched chamber with vegetation and objects to explore rather than in a barren chamber in the same tank. When Sneddon injected zebrafishes with acetic acid, this preference didn’t change; nor did it change for other zebrafishes injected with saline water (which  causes only brief pain). However, if a painkiller was dissolved in the barren, unpreferred chamber of the tank, the fishes injected with the acid chose to swim in the unfavorable, barren chamber. The saline-injected fishes remained in the enriched side of the tank. Thus, zebrafishes will pay a cost in return for gaining some relief from their pain.”

Balcombe stressed this test's significance in proving that fish are conscious and feel pain. He told SeafoodSource, “Fishes who were injected with something potentially painful (acid) left the safety of their home tank to go to a place they normally avoid (a barren chamber with nowhere to hide) where the scientists had dripped a painkiller (lidocaine).”

Further evidence of fish consciousness is seen in fish-hunting alliances, Balcombe wrote in his book. He cites research that shows “groupers and moray eels...using signals or gestures to communicate their desires or intentions, and adopting complementary roles to catch prey.”

This research, by Université de Neuchatel Professor of Eco-ethology Redouan Bshary and three colleagues, showed roving coral groupers from the Red Sea used a “rapid, full-body shimmy” to recruit giant moray eels to hunt with them.

“The two teammates swim off over the reef like friends on a stroll. The researchers saw dozens of these interactions, and they were able to show that groupers and morays who worked as a team caught more prey fishes than either hunter working alone,” Balcombe wrote about Bshary’s findings. “It is two fish minds working in concert to translate and transfer desires and intentions into favorable outcomes.”

Balcombe’s book turns to tackling the thorny question of fish sentience in depth by introducing the issue of nociception, described as behavior “due to the actions of peripheral nerves working independently of the brain.”

“Scientists use the term nociception to describe a reflex that in itself involves no awareness or pain,” Balcombe writes in his book. “Nociception is the first stage in pain sensing – necessary but not sufficient for the experience of pain. It is only when information from nociceptors is relayed to higher brain centers that it hurts.”

Balcombe dismisses Rose's assertion that only creatures with a neocortex can feel pain. He said it is disproved by the fact that birds, which have no neocortex, are generally considered to be creatures that demonstrate consciousness and self-awareness, Balcombe said.

“If any animal without a neocortex is nevertheless conscious, it disproves the notion that a neocortex is required for consciousness.”

But in his study, Rose highlighted research showing that animals whose brains and cortex were removed demonstrated emotional responses similar to those shown by the fish in Sneddon's experiments. These emotions are “unconscious...behavioral, hormonal, and neural responses to positive or aversive stimuli or situations.”

“They provide the basic raw material for processing by the higher cortical regions, which in turn produces conscious feelings,” Rose wrote. “It is only when these unconscious emotional responses are processed by the cortical regions that exist in humans, but not in fish, that there is conscious experience of suffering in pain.”

Just as nociception differs from conscious pain, so emotions differ from feelings. Understanding this difference “is fundamental to understanding the difference between fishes and humans in their capacities for experiencing pain or conscious suffering,” Rose said.

“Consequently, none of these tests [of fish sentience] can be legitimately viewed as tests of pain, because the target behaviors can be expressed without consciousness,” he wrote.

But the debate seems far from over.

Balcombe counters Rose's argument by asserting that the pallium, which is found in the brains of fish, is equivalent to the neocortex. 

“While there is less computational power in the average fish pallium than in the average primate neocortex, it is increasingly apparent that the pallium serves functions for fish that the neocortex does for mammals and the paleocortex for birds,” he said.