Bivalves like mussels and oysters are farmed at massive scale with almost no welfare regulation, and their sentience status remains scientifically debated but increasingly considered seriously.
The welfare status of bivalves is genuinely uncertain, which makes them philosophically unique among farmed animals. Current scientific consensus does not support strong evidence for bivalve sentience, and some animal welfare advocates include them as relatively ethical seafood choices. However, the precautionary principle suggests some caution is warranted as understanding of invertebrate cognition advances. From a purely environmental perspective, bivalve farming is genuinely low-impact compared to other animal protein sources. Continuing welfare research on invertebrate sentience is the most important step toward evidence-based policy.