“Fish can feel pain”

For a long time, it was widely assumed that fish, unlike mammals, did not experience pain. This common misconception likely stemmed from their seemingly impassive expressions, the vast differences in their aquatic environment, and their distinct brain structures compared to humans. Early philosophical views, such as those by René Descartes, also contributed to the idea that animals, particularly those perceived as "simpler," lacked consciousness and thus the capacity for suffering. It was difficult for people to empathize with creatures so unlike ourselves, reinforcing the belief that their responses to injury were merely reflexive.

However, scientific research has increasingly challenged this view. Pioneering studies, notably by Dr. Lynne Sneddon, identified nociceptors—nerve endings that detect potentially damaging stimuli—in the tissues of fish, similar to those found in mammals. Furthermore, fish exhibit complex behavioral and physiological responses to harmful events. They may avoid noxious stimuli, rub injured areas, show altered swimming patterns, or display reduced activity and appetite, all of which are mitigated by pain-relieving drugs like morphine. These responses suggest more than just a simple reflex; they indicate an active process of detecting and reacting to potential harm.

Despite this growing body of evidence, the debate continues over whether fish subjectively "feel" pain as mammals do, with an emotional component of suffering. Some arguments against fish pain often point to the absence of a neocortex in fish brains, a structure associated with higher consciousness in mammals. However, scientists argue that assuming a neocortex is essential for pain in all animals is anthropocentric, as different species may have evolved different brain structures to achieve similar functions. While the exact subjective experience remains challenging to prove, the physiological and behavioral data strongly suggest that fish do indeed have the capacity to experience something akin to pain, making the verdict "plausible."