Evidence for pain and sentience in aquatic invertebrates is growing, challenging traditional assumptions about their welfare significance.
The extension of welfare consideration to aquatic invertebrates marks a significant expansion of our moral circle based on emerging evidence. Decapod crustaceans demonstrate avoidance learning after noxious stimuli, self-protect injured areas, and alter behaviour in ways consistent with pain experience. Cephalopods show even more complex cognition, with octopus problem-solving, play behaviour, and individual recognition now documented. Welfare-positive handling and killing of crustaceans requires stunning before cooking; storage on ice slurry rather than live holding in poor conditions; and humane killing using sharp instruments or electrical devices. Cephalopod welfare in captive research settings requires enrichment, social management, and minimising painful procedures.