The freshwater pearl mussel is one of Britain's most endangered species, with most populations in sharp decline due to water quality deterioration and the loss of juvenile survival conditions.
Freshwater pearl mussel conservation raises questions about invertebrate welfare that are only beginning to be addressed. While the species' capacity for subjective experience is uncertain, the scale of population collapse - from millions to a few thousand individuals - represents a biological catastrophe. Individual mussels in degraded rivers face physiological stress from elevated nutrient and sediment loads that reduce gill function and metabolic efficiency. River restoration that reduces silt and nutrient input is the most direct welfare-positive action, alongside protection of host salmon and trout populations on which juvenile mussels depend.