The freshwater pearl mussel (Margaritifera margaritifera) is one of Britain's most threatened invertebrates, with Scottish rivers holding the last viable UK populations. As a species that can live for over 130 years, its welfare and survival require clean, fast-flowing rivers with salmon and trout host fish for larval development.
Freshwater pearl mussels caught during illegal pearl fishing die from being prised open and having their soft tissues searched for pearls — a direct welfare harm to a protected species. Water quality deterioration causes physiological stress through fine sediment blocking feeding currents and algal blooms reducing dissolved oxygen. Mussel welfare depends on river restoration: reducing agricultural runoff that causes siltation, fencing riverbanks to reduce cattle-caused bank erosion, and restoring native riparian woodland. Captive rearing programs supplement wild populations by rearing juvenile mussels in controlled conditions before seeding into restored river sections.