Bivalve molluscs including mussels and oysters are farmed in enormous quantities, with their welfare status scientifically contested and ethical frameworks evolving.
Bivalve welfare science is genuinely contested - unlike fish, crustaceans and cephalopods where evidence for pain experience is building strongly, bivalves present a genuine philosophical and scientific open question about whether any morally relevant experience is possible given their neural architecture. This uncertainty means the welfare case for bivalves is much weaker than for other animal groups. The environmental argument cuts both ways: bivalves grown in well-managed farms have minimal ecological footprint, making them among the most ethical animal protein sources by environmental measures. From a pure welfare perspective, the absence of strong sentience evidence, combined with minimal farming suffering risk, makes bivalves a relatively low welfare concern compared to vertebrates and decapod crustaceans.