Research into fish cognition has revealed surprising complexity — tool use, social learning, numerical discrimination, and deception — with direct implications for how we treat billions of fish annually.
The emerging picture of fish cognition challenges the assumption that simple nervous systems mean simple experience. Fish form memories spanning months, recognize social partners, solve multi-step problems, and respond to their own injuries with protective behaviors and analgesic-responsive pain responses. Whether fish have rich subjective experience remains scientifically debated, but the behavioral evidence demands that we take their potential suffering seriously. The scale of human impact on fish — through fishing, farming, and habitat destruction — means that even moderate probabilities of fish suffering represent enormous aggregate welfare costs.