Mussels and oysters are increasingly considered lower-welfare-concern food sources but their sentience remains scientifically uncertain and deserves consideration.
Bivalve welfare occupies the lowest rung of the welfare uncertainty ladder for commonly consumed animals. These animals lack centralized nervous systems, and the probability of morally relevant experience appears lower than for any vertebrate. For those reducing animal product consumption for welfare reasons, bivalves are often considered a reasonable compromise — much lower welfare risk than fish or birds while still providing animal protein. This does not mean their welfare is definitively zero, only that our uncertainty is high and risk appears low.