We all know fish and other underwater creatures can't talk; despite fanciful films like The Incredible Mr. Limpet (1964) starring Don Knotts, The Little Mermaid, Finding Nemo, and other fishy tales that depict sea creatures speaking; fish, crustaceans, and invertebrates communicate visually and chemically. The question is, can fish feel pain? According to some scientific researchers, our piscine friends can't feel a thing. Let's investigate a little further with a look at the current debate.
The Definition of Pain
As humans, we can feel suffering on a lot of different levels, and so can other mammals, birds, and creatures with large, highly evolved brains. Lynne Sneddon, a professor of animal biology at England's University of Liverpool published a study in which she intentionally tried to produce pain, defined as equal parts of physical and emotional suffering, in fish. This type of pain is well documented in creatures with complex brains.
The Experiment
Using four groups of rainbow trout for her study, the professor injected some with bee venom and some with acetic acid. Some were injected with saline as a control group simply to find out how the fish reacted to a needle poke in the snout without a pain-inducing agent, and the fourth group were handled but were not subjected to needles; this fourth control group was used to rule out the stress of the experiment as the cause of the fishes reaction.
The injection site was chosen intentionally to test the importance of a group of nociceptors, which are neurological sensors around the fishes' mouths. During the course of her research, Professor Sneddon has identified 58 of these sensors around the fishes' faces and heads which are triggered by chemical, temperature, and mechanical stimulation. The sensors are hard wired into the fishes' amygdala-like hind brain, which unconsciously controls such things as movement, involuntary reflexes, eating, breathing, circulation, and more - it is the central processing unit that "runs" the fish. During her studies, the professor found that the nociceptors caused an unconscious pulling away from things that might damage the body, preventing fish from impaling themselves on sharp objects or running head first into life-endangering situations.
Despite a study published by the University of Wyoming's James Rose of the Department of Psychology, Physiology, and Zoology, who has studied the neurological structure of a fish brain and who says fish don't have the right kind of brain structures to feel pain, the fish in Sneddon's study displayed what appeared to be thoughtful reactions to the stimuli they were made to feel. The trout displayed a rocking motion much like that which stressed animals with better evolved brains will display, and they rubbed their faces on their tank walls and in the gravel at the bottom of the tank in an apparent attempt to end the discomfort they were feeling. Sneddon then injected the uncomfortable trout with morphine to find out whether the behaviors would cease once the sensations were dulled, and once injected, the trout stopped displaying behaviors that indicated discomfort.
While Professor Rose of the University of Wyoming believes fish do not have the right kind of "hardware" for consciousness that would allow them to feel pain, Sneddon's research shows that many species do have the right neurological structures to allow them to feel pain; some are even equipped with the ability to produce neuropeptide opiates which respond appropriately to pain relieving agents; the trout and other bony fishes do possess these. Cartilaginous fishes like sharks and rays do not possess nociceptors, so Sneddon's research shows that they probably do not feel pain as higher animals do.
In the end, it all comes down to the definition of pain. It's either a stimuli suggesting danger to the body that signals the brain that escape is necessary, or it is a deeply felt sensation that causes distress. The two professors disagree about whether this pain is consciously felt, but they do agree on one thing; that is, fish require certain conditions for health and survival. Clean water, appropriate temperatures, a healthy, natural diet, and room to move are basic requirements. If we care about fish, we must treat them and their environment with respect or risk the consequences, which ultimately include devastation for us all.