Bivalve molluscs including oysters, mussels, and clams have uncertain welfare status due to their simple nervous systems, with the precautionary principle informing how harvesting practices should be evaluated.
Bivalve welfare occupies an ethically interesting middle ground. The evidence for sentience is weak relative to vertebrates and crustaceans, making bivalves potentially acceptable to people concerned about animal welfare who avoid other animal products. However, the precautionary principle suggests that where uncertainty exists, minimizing potential harm is appropriate. Dredging-based wild harvest causes significant habitat damage affecting welfare of other species regardless of bivalve welfare status. Aquaculture of bivalves has genuine environmental and potential welfare advantages over other animal foods. The ethical status of bivalves deserves ongoing scientific attention as welfare science develops.