Accumulating evidence for fish intelligence and learning challenges the assumption that fish do not suffer.
The scientific case for fish sentience has strengthened considerably. Fish demonstrate learning, memory, problem-solving, and responses to damaging stimuli consistent with pain experience. Social fish species show distress when isolated. These findings challenge the dismissal of fish welfare that has historically justified their use in ways unthinkable for mammals. Given the enormous numbers of fish affected by human activities, even small improvements in fish welfare standards would benefit an extraordinary number of animals.