Mussels, oysters, scallops, and other bivalves are farmed in enormous quantities, with ongoing scientific debate about their sentience and welfare implications.
Bivalve sentience sits in a genuinely uncertain scientific space. Unlike vertebrates or decapods where the evidence for pain experience is strong, the evidence for bivalve sentience is mixed and contested. They lack the centralized nervous systems associated with conscious experience in better-studied animals. This uncertainty creates an interesting ethical situation: how much moral consideration do we owe to organisms that may or may not experience suffering? For those who apply precautionary principles, even uncertain sentience in animals produced at 17 million tonnes per year warrants attention. For others, the environmental benefits of bivalve aquaculture combined with uncertain sentience make them preferable to most other animal protein sources.