Do fish feel pain?

Scientists still debate that question.

But the belief by some that fish do experience pain contributes to the debate over whether the state should end Hawaii’s aquarium trade.

While most of the arguments focus on scientific, economic or cultural factors, ethical issues increasingly are being raised, especially as more research is done in the field.

“There is now evidence that fish experience negative effects of pain,” Victoria Braithwaite, professor of fisheries and biology at Penn State University, said in an email to the Honolulu Star-Advertiser.

Several experiments involving different species have shown that tissue damage has an effect on fish at a physiological and cognitive level, prompting them to change simple and more complex behaviors, according to Braithwaite.

“Interestingly, providing the fish with some form of pain relief can prevent the negative responses to tissue damage,” she wrote. “This strongly suggests that the fish do feel the pain, but providing pain relief reverses that effect.”

Richard Pyle, a Bishop Museum researcher and associate zoologist, said fish brains are so tiny that the fish don’t experience emotions to nearly the same degree as mammals.

Because of the lack of complex wiring in their brains, the pain that fish might experience would not in any way be comparable to what mammals experience, Pyle added.

Questions about suffering usually emerge when trade opponents voice concerns about how captured animals are treated.

Depending on the size of the fish, some collectors will clip protruding spines to lessen the chance the spines puncture the plastic bags holding the fish during shipment.

And depending on the depth at which the fish are caught, some collectors will pierce the animals’ internal swim bladders with a hypodermic needle to allow gas to escape, lessening the chance of problems related to the fish surfacing too quickly.

When the fish are prepared for shipment, they typically are not fed for several days to minimize harmful waste polluting the water during transit.

Gail Grabowski, a Chaminade University associate professor and environmental studies director, said removing fish from their natural habitats to be shipped thousands of miles away for ornamental purposes is wrong on multiple fronts, including the stress-inducing ways the fish are handled.

“It’s mean,” she said. “It’s so not compassionate.”

Rene Umberger, executive director of For the Fishes, a nonprofit that advocates for ending commercial collection of aquarium fish, said there are more humane — though more expensive — ways to treat the animals rather than cutting their spines, puncturing an internal organ or shipping the fish in small bags with minimal water.

“These are all money-saving things that hurt the fish,” Umberger said.

Collectors, however, defend their methods, saying they are driven by best practices, not financial gain. Cutting a spine, they said, is akin to a person’s nails being clipped, and puncturing the swim bladder is akin to a child getting an immunization shot.

Pyle, who has handled thousand of fish for his research work, said Hawaii collectors are known for treating their fish well and for providing customers with high-quality specimens.

“It’s the gold standard for how this industry should be run,” he said.

If a collector engages in practices that harm the fish, that will affect quality, and if it happens frequently enough, the collector’s reputation and business will suffer, according to Pyle. That serves as an incentive to follow best practices, he added.

Beyond concerns about treatment, trade opponents raise a more fundamental question: Should the fish be taken from their natural habitats in the first place, only to be sold and then placed in a hobbyist’s aquarium?

Bob Likins, spokesman for the Virginia-based Pet Industry Joint Advisory Council, said aquariums provide multiple benefits to owners and others. They increase awareness of marine habitats and nature, and studies show they provide health benefits to owners, such as lowering blood pressure, according to Likins.

What’s more, the science of maintaining aquariums has improved substantially over the years, resulting in better environments for the fish, according to Pyle.

“Modern aquariasts are spectacularly successful in maintaining opulent conditions,” he said. “It’s not like a prison.”

But Braithwaite, the Penn State professor, takes a different view.

“Removing a fish from a natural habitat and transferring it to a small aquarium is likely to be detrimental for many fish that would normally swim over areas of a natural reef to explore and find food,” she said. “The confines of a small hobbyist aquarium tank would simply not allow the fish to behave in ways that the fish do in the wild.”

From that perspective, Braithwaite added, stocking aquariums with “fish that have been bred in smaller tanks in captivity would be better.”