Nov 12, 2026 Do Fish Feel Pain?
A fish is caught on a hook. It struggles to escape, but does it actually feel pain? Or are its struggles automatic behaviors that occur without any conscious experience?
Behind that seemingly simple question lies a much bigger one: Does feeling pain require a mammalian-style brain with its neocortex, or can pain feelings be generated in different nervous system structures?
Scientists have debated the issue of fish pain for decades. The modern debate can be traced at least back to the 1960s, when a prominent South African ichthyologist argued that fish lacked the brain structures necessary to experience pain.
That argument would reappear over the next half-century, challenged by discoveries about fish nervous systems and changing ideas about how consciousness itself arises.
An Early Argument Against Fish Feeling Pain
- L. B. Smith was a South African ichthyologist best known for identifying a remarkable fish discovered in 1938 as a coelacanth. This “living fossil” was known from fossils but had long been thought extinct. Smith was also an avid angler and, in response to campaigns against angling in South Africa in the 1960s, Smith argued that one should distinguish between evolutionary stagnant and primitive animal species and advanced animals. Fish, he contended, were primitive species who lacked the frontal lobes, the neocortex, found in mammals and could not, as a result, feel pain.
Smith’s argument is archaic and loaded with prejudice but his focus on brain structures is still central to the modern fish pain debate. If fish lack the brain structures associated with conscious pain in humans, can they experience pain at all?
The issue then moved from scientific debate into public policy. West Germany’s 1972 Animal Welfare Act prohibited causing animals pain, suffering, or harm without good reason. Beginning in the 1980s, court cases and regulatory debates considered how that principle should apply to fishing practices, particularly fishing competitions and catch-and-release angling. This debate then moved to the United States in the late 1990s as animal protection organizations challenged angling practices. Neuroscientist James D. Rose was commissioned by the American Fisheries Society to produce a review of the issue. That review was published in 2002 in the Society’s journal.
Rose maintained that awareness of pain in humans depends on functions performed by particular regions of the mammalian cerebral cortex. Because fish lack those regions and, in his view, any functional equivalent, he concluded that fish cannot and do not consciously experience pain.
Detecting Harm or Feeling Pain?
Rose’s argument rests on an important distinction between nociception and pain.
Nociception is the nervous system’s detection of potentially harmful stimuli. It may produce a protective response, such as withdrawal, without necessarily demonstrating a conscious experience of pain.
Researchers including Victoria Braithwaite and Lynne Sneddon challenged the conclusion that fish cannot feel pain. In 2003, Sneddon, Braithwaite, and Michael Gentle reported finding nociceptors in rainbow trout. These sensory nerve fibers respond to external stimuli that may cause harm to bodily tissues. Nerve signals passed up the nociceptor fibers elicit protective behaviors. However, the actual feelings of pain are generated in the central nervous system. Some neuroscientists hold that the neocortex is essential for pain feelings while others argue that structures in non-cortical parts of the central nervous system are involved in generating actual pain feelings.
The studies of fish responses to noxious stimuli also observed prolonged physiological and behavioral changes after the trout were exposed. The fish took longer to resume feeding, showed unusual behavior, and experienced increased ventilation rates. In related research, Sneddon reported that morphine reduced several of these responses.
These findings provided evidence that fish detect potentially harmful stimuli and respond in ways that extend beyond an immediate withdrawal reflex. They did not, however, eliminate the deeper scientific question: Do fish consciously experience those events as pain?
The Debate Comes to Animal Sentience
In 2016, the disagreement became the subject of the third target-article discussion published in Animal Sentience, an academic journal published by WellBeing International.
Animal Sentience is a peer-reviewed, cross-disciplinary, open-access journal devoted to the capacity of nonhuman animals to feel. It publishes target articles followed by expert commentaries examining the scientific, practical, ethical, philosophical, and legal implications of the target article. The original author[s] are urged to respond to those commentaries.
The goal is not to determine a winner by popular vote. It is to place competing evidence and interpretations side by side and allow the scientific arguments to develop through a curated and informed debate.
In his target article, Australian neuroscientist Brian Key argued that fish lack the neural architecture and connectivity necessary for feeling pain. His paper generated more than 40 commentaries, most of whom challenged Key’s arguments. Some argued that the absence of a mammalian neocortex does not demonstrate that fish are incapable of pain. Others examined fish behavior, evolutionary evidence, welfare implications, and the difficulty of using the mammalian brain as the sole model for conscious experience.
Scientific questions, however, are not resolved simply by counting the number of experts on each side. The arguments and evidence must be examined on their merits.
More Than One Pathway to Feeling?
Key and Rose both emphasized the importance of cortical structures associated with conscious pain in humans. Other neuroscientists question whether the mammalian neocortex is the only possible foundation for conscious experience.
Antonio Damasio and Hanna Damasio, for example, have proposed that consciousness is rooted in homeostatic feelings arising from interactions between the nervous system and the body’s internal processes. In the Damasios’ account, feelings such as hunger, pain, and physical well-being played a foundational role in the evolution of consciousness.
This opens a different possibility: Fish may not need a mammalian-style brain to have meaningful subjective experiences.
A Question Larger Than Fish
The debate remains difficult because scientists cannot directly access the experience of another animal, just as we cannot directly experience the consciousness of another person. Instead, scientists must draw careful conclusions from anatomy, nervous-system function, behavior, evolutionary history, and responses to injury and pain-relieving drugs.
The discussion is also expanding beyond fish. Scientists are examining evidence of sentience in cephalopods, decapod crustaceans, insects, and other animals that do not possess a neocortex.
This broader research raises an important question: Are we looking only for the structures associated with human experience, or could evolution have produced more than one pathway to feeling?
The answer has consequences beyond the laboratory. It can influence fishing practices, aquaculture, animal welfare policies, food production, and the treatment of billions of aquatic animals.
In the next episode of WBI’s podcast, we will explore the evidence and arguments on both sides of this continuing scientific debate. Do a fish’s responses to injury reflect a conscious experience of pain, or an effective but nonconscious system for detecting and escaping harm? And how can we recognize sentience in animals whose brains are very different from our own?
Video Credit: Charlotte Bleijenberg, iStock