Fish in aquariums and zoo exhibits are often afforded minimal welfare consideration, yet they are sentient animals whose needs for appropriate water quality, space, social groupings, and enrichment are frequently unmet.
Fish welfare in public aquariums is often an afterthought compared to the welfare consideration given to mammals and birds in the same institutions. Yet fish are sentient animals with species-specific social, spatial, and environmental needs. Large pelagic species — sharks, tunas, billfishes — have home ranges and swimming speeds fundamentally incompatible with any tank size achievable in a public facility. Schooling fish kept below their natural group sizes show heightened stress and abnormal behaviour. Water quality management is critical: chronic sub-optimal parameters cause physiological stress and immunosuppression without obvious visible signs. The public welfare messaging that zoos and aquariums promote is sometimes undermined by the conditions of their own fish exhibits, making internal welfare assessment and improvement a credibility issue as well as an ethical one.