Fish welfare in aquaria receives far less attention than mammal welfare despite evidence of fish sentience, pain experience, and complex behavioral needs.
Fish welfare in aquaria is often overlooked due to historical assumptions that fish are simple, non-sentient animals without meaningful pain experience. This view has been substantially revised by neuroscience showing fish possess the neurochemical and behavioral substrates for pain experience and negative affect. Fish in inappropriate social groupings show aggression and stress. Inadequate tank size for highly mobile species causes behavioral restriction. Water quality parameters including oxygen, temperature, and pH directly affect physiological welfare. Capture and transport stress can be lethal or cause chronic immune suppression. Progressive aquarium facilities are implementing welfare assessment frameworks for fish that parallel those used for mammals, representing an important advance in recognizing fish as welfare-significant animals.