Why Should We Care about fish?
A sentient being is one that has some ability to evaluate the actions of others in relation to [her]self and third parties, to remember some of [her] own actions and their consequences, to assess risk, to have some feelings and to have some degree of awareness. These abilities can be taken into account when evaluating welfare. There is evidence from some species of fish, cephalopods and decapod crustaceans of substantial perceptual ability, pain and adrenal systems, emotional responses, long- and short-term memory, complex cognition, individual differences, deception, tool use, and social learning. The case for protecting these animals would appear to be substantial.
-Donald Broom, Emeritus Professor of Animal Welfare at Cambridge University, in Cognitive ability and sentience: Which aquatic animals should be protected? (2007)
fish feel pain
Fish are sentient individuals. They feel pain, fear, and can suffer. Scientific studies have shown that fish can feel pain. (The latest discussion of these studies can be found in Animal Sentience: An Interdisciplinary Journal on Animal Feeling Volume 1 from 2016.)
Pain can be broken down into two parts: nociception (whether fishes have receptors to detect pain) and the cognitive response to that pain (how their brain processes it). Fishes have the receptors to detect painful stimuli, and even though their brain is not exactly like ours, it can still process pain.
Fish are vertebrates, like birds and mammals; so they respond to pain and fear the same way a dog or cat does, in the way that their body reacts, and in the way their behavior changes. After fishes were injected in the lips with bee venom, their gills beat faster, they rocked side to side, and they rubbed their lips on the side of the tank. After they were given painkillers, their breathing returned to normal and they stopped rubbing their faces.
fish are smart
Fish are far more intelligent than we give them credit for. There is a big gap between how we perceive fish and scientific reality. In fact, fishes’ cognitive abilities are often as good or better than other animals’. Many behaviors of primates can even be found in fish!
Fish have excellent long-term memories, can use tools (catfish use leaves as a “baby carriage” to transport their eggs), hunt cooperatively, learn by observation, help their friends by watching their back while they eat, cheat, deceive and punish each other, eavesdrop, develop complex traditions, and even have culture (meaning they can learn novel behaviors from one another). Fish who live in areas that are heavily fished are even clever enough to start to learn to escape being caught by avoiding fishing gear and hooks. Most importantly, fish can learn and remember complex information, which means they can suffer.
Fish Welfare by Edward J. Branson (2008)
Do Fish Feel Pain? by Victoria Braithwaite (2010)
Fish Intelligence, Sentience and Ethics by Culum Brown (2015)