Bivalve molluscs including mussels, oysters, and clams are consumed in enormous quantities and are grown in aquaculture, raising welfare questions that are complicated by uncertainty about their capacity for subjective experience.
Bivalve welfare presents a philosophically interesting edge case in welfare science. The absence of a centralised nervous system suggests that the complex pain processing found in vertebrates and crustaceans is absent. However, their stress responses indicate some form of nociception. The precautionary principle approach would suggest treating any possibility of sentience as morally relevant, though the probability is considered low by most welfare scientists. If bivalves do have minimal or no subjective experience, they may represent a genuinely welfare-positive animal protein source, which has implications for dietary recommendations from an animal welfare perspective.