Debate continues over whether fish feel pain

Published on December 17, 2014
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Do fish feel pain? Can they suffer?

Historically, the opinion on both counts has been that they don’t, but these views are rapidly evolving as scientific evidence expands.

That fish respond to injurious stimuli unconsciously and aren’t actually aware of pain is a view championed most notably by James Rose, PhD, professor emeritus of zoology at the University of Wyoming.

In a 2014 article titled “Can fish really feel pain?” published by the journal Fish and Fisheries, Dr. Rose concludes that research suggesting fish are conscious of pain is unsubstantiated and lacks adequate empirical support.

Aquaculture is the fastest-growing animal food–producing sector in the world. The traditional view is fish aren’t conscious of pain and, therefore, are unable to suffer. Research showing otherwise is gaining traction within the veterinary and scientific communities, however.

He writes in favor of function- and nature-based welfare standards predicated on objective indicators of fish well-being “rather than a feelings-based standard that is highly speculative and scientifically unsubstantiated.”

In contrast, the veterinary and scientific communities are increasingly warming to the possibility that pain for some fish species is a more noxious experience than an unconscious, knee-jerk response. Concerning fish, the AVMA Guidelines for the Euthanasia of Animals state: “Considerable evidence is accumulating suggesting it is appropriate to consider the possibility of pain perception in these species.”

The Institute for Laboratory Animal Research in 2009 devoted an entire journal issue to the matter because, as Dr. Lysa Pam Posner explained, of the “growing acceptance in the scientific community that fish neuroanatomy and behavioral responses reveal that these animals feel pain.”

“It would then be logical to conclude that an animal that can feel pain can also experience distress. It is likely that humans will never fully know the extent to which fish feel pain, but acknowledging that they do raises the likelihood that fish will receive the humane treatment increasingly provided to vertebrates,” wrote Dr. Posner, an associate professor of veterinary anesthesiology at North Carolina State University College of Veterinary Medicine.

The issue was one of several explored at the AVMA animal welfare symposium titled Humane Endings. The meeting was held Nov. 3-5, 2014, in suburban Chicago. Best practices for euthanasia were discussed and research aimed at refining humane killing methods was examined for the purpose of ever-refining the AVMA euthanasia guidelines.

Dr. Roy Yanong, a professor and extension veterinarian with the Tropical Aquaculture Laboratory at the University of Florida, explained at a symposium presentation how developing euthanasia recommendations for fish is especially challenging, considering the world is populated by more than 30,000 fish species with diverse physiologic and anatomic characteristics, living in a broad spectrum of water temperatures and salinity concentrations.

“The biological and taxonomic diversity within the piscine world makes it a lot more complicated to come up with guidelines that cover every single species, even more so than other classes of animals,” said Dr. Yanong, who is also the Aquatics Working Group lead for the AVMA Panel on Euthanasia.

The uses for fish are numerous: for food and sport, as pets and for display, and in research and education. They are important components of healthy ecosystems. In the United States, ornamental fish and aquaculture are billion-dollar industries. Aquaculture is also the fastest-growing animal food–producing sector in the world and continues to outpace population growth, according to the Food and Agriculture Organization of the United Nations.

In the area of research, fish are the third most commonly used animal after mice and rats. Zebrafish are used in studies of genetics, human diseases, stem cells, toxicology, neurobiology, and more.

Notably, fish are not covered by the federal Animal Welfare Act or Humane Slaughter Act, which regulate the treatment of animals used for research and food production, respectively. Additionally, of the drugs listed in the AVMA guidelines for fish euthanasia, including tricaine methanesulfonate, benzocaine, isoflurane, sevoflurane, pentobarbital, ketamine, and propofol, none is approved by the Food and Drug Administration to kill fish.

Dr. Stephen Smith, a professor of aquatic medicine and fish health at the Virginia-Maryland Regional College of Veterinary Medicine, was also a presenter at the AVMA symposium. He acknowledged the difficulties of determining whether fish feel pain, but he believes the empirical evidence that fish can detect, perceive, and respond to injurious stimuli is compelling.

“Why do we really care if fish feel pain? Fish are vertebrates, and there’s some ethical awareness as humans for other vertebrates,” Dr. Smith said. “A lot of the common techniques used in fish, if they had been used in humans, are associated with pain. So we have to consider that as one of the paramount issues when working with these animals. The veterinary and scientific communities have a responsibility to address the welfare of these fish.”

Related JAVMA content:

The ethics of pain management in animals (Dec. 15, 2001)