Bivalves including oysters, mussels and clams are farmed at enormous scale with no welfare consideration - the science of bivalve sentience is complex and contested.
Bivalve welfare sits at the frontier of sentience science. The neurological evidence - no centralised brain, limited nociceptor systems - suggests low probability of sentience. However, the scale argument applies: if there is any probability of suffering, the enormous scale of bivalve production creates non-trivial aggregate welfare concern. Welfare advocates apply different thresholds here - some argue the precautionary principle supports welfare consideration, others argue the evidence base is insufficient to justify welfare measures. Scientific research into bivalve responses to noxious stimuli and any centrally processed nociception continues. Consumers can hold these uncertainties with intellectual honesty rather than forcing false certainty.