Fish do feel pain, calling into question how humans treat them

Fish have nervous system receptors that respond to pain in a “strikingly similar” way to other mammals, according to a new review. 

The research, published in the journal Philosophical Transactions of the Royal Society B and authored by Dr. Lynne Sneddon, the Director of Bioveterinary Science at the University of Liverpool, calls into the question the way people handle and kill fish. 

Nociception describes the ability to detect harmful stimuli. Nociceptors are found throughout the skin, bones, and muscles. While nociception in mammals has been well established, there is considerable debate about the extent to which fish feel pain. 

Because fish have a single-layered forebrain, researchers have questioned whether or not fish feel pain in the way that humans or other vertebrates with complex brains might. 

According to Dr. Sneddon, studies have shown that aquatic vertebrates will avoid dangerous areas for days even if it means going without food. 

Goldfish given an electric shock in an area of their tank will avoid that area and starve themselves in the process rather than risk another shock. 

Another indicator that fish feel pain is that a perch will cut back on feeding after being caught on a hook because it is too painful to eat.

Dr. Sneddon also cites examples of fish seen hyperventilating or rubbing their bodies against different objects as if to self-soothe. 

Imagine stubbing your toe or getting a paper cut. It’s instinctual to hold or rub the sore area. Now, mounting evidence is showing that fish respond in similar ways to their injuries. 

“When subject to a potentially painful event fishes show adverse changes in behaviour such as suspension of feeding and reduced activity, which are prevented when a pain-relieving drug is provided,” said Dr. Sneddon. “When the fish’s lips are given a painful stimulus they rub the mouth against the side of the tank much like we rub our toe when we stub it.”

The review also found that fish respond to painkillers. Zebrafish, for example, have been shown to resume their normal swimming patterns after being exposed to hot water once a pain reliever was added to their tank. 

It’s not a matter of whether or not fish feel pain as Dr. Sneddon’s review confirms that fish experience pain much in the same way other vertebrates do. However, if fish feel pain, then we need to ensure that our treatment of aquatic vertebrates is ethical and humane. 

“If we accept fish experience pain, then this has important implications for how we treat them,” said Dr. Sneddon. “Care should be taken when handling fish to avoid damaging their sensitive skin and they should be humanely caught and killed.”

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By Kay Vandette, Earth.com Staff Writer 

Image Credit: Shutterstock/Rocksweeper