Public aquariums house millions of fish, invertebrates and marine mammals annually, with welfare standards that vary enormously between institutions and receive less scrutiny than terrestrial zoos.
Aquarium welfare sits in a regulatory and cultural space that has historically received less attention than terrestrial zoo welfare. Fish in tanks that are too small, with inadequate water quality or inappropriate social grouping, experience chronic stress. Marine mammals including dolphins and beluga whales face welfare challenges related to acoustic environment, social group management and the mismatch between their cognitive and physical needs and the captive environment available. The welfare case for aquariums that house highly social, cognitively complex species is weakest where those species have well-documented poor welfare outcomes in captivity. Welfare improvements require species-specific space requirements, enrichment standards, and transparent welfare reporting comparable to terrestrial zoo requirements.