Freshwater mussels are among the most endangered groups of animals globally, with habitat degradation and water quality decline causing mass die-offs that may involve significant welfare harm to millions of individuals.
The welfare status of freshwater mussels is uncertain but increasingly relevant as evidence accumulates that bivalves may have nociceptive responses. Mass mortality events during environmental extremes — where thousands of mussels are observed gaping and dying in warming, deoxygenated water — may involve suffering at scale. Regardless of their sentience status, the ecological roles mussels play make their protection valuable for the welfare of the many species that depend on clean freshwater ecosystems.