The welfare status of bivalves - oysters, mussels, clams, and scallops - remains scientifically uncertain, with this uncertainty having important implications for aquaculture ethics.
Bivalve welfare sits at the most uncertain edge of the sentience spectrum. Unlike fish and crustaceans, where evidence for nociception and possible pain experience is substantial, bivalve evidence is more ambiguous. The precautionary principle suggests some consideration is warranted given the enormous numbers harvested. Most welfare researchers treat bivalves as lower priority than species with clearer evidence of sentience.