Scallops and oysters are farmed at enormous scale, but their capacity for sentience is genuinely uncertain, making welfare guidance for bivalve consumption particularly challenging.
Bivalve welfare occupies a unique position in welfare ethics: unlike virtually all other farmed animals, the evidence tentatively supports (rather than contradicts) the position that these species may not have welfare-relevant subjective experiences. This is not certainty — the science of invertebrate consciousness is young — but the probability estimate is different from that for vertebrates or even decapod crustaceans. For those with welfare concerns about animal foods who are looking for low-risk options, farmed bivalves represent an interesting case: high-protein, nutritious foods with low environmental footprint and uncertain but probably low welfare cost. The precautionary principle still argues for good handling and rapid killing, but the moral weight attached to bivalve welfare is appropriately lower than for fish or mammals.