Freshwater Pearl Mussel

The marvellous long-lived Freshwater Pearl Mussel is critically endangered because our rivers are in a poor state.


Freshwater Pearl Mussels (Margaritifera margaritifera) are magnificent bivalves that live in rivers with exceptionally clean water and lots of healthy wildlife. Pearl Mussels are spectacularly long-lived, often over a 100 years, and have a fascinating life cycle. Baby pearl mussels need healthy populations of trout and salmon and live harmlessly in the gills of these fish, enjoying a safe, oxygen-rich nursery until they are big enough to begin life in the riverbed. In return, large populations of the filter-feeding pearl mussels help clean up the water. A healthy population of Freshwater Pearl Mussels shows that a river and all its wildlife are doing well.


Freshwater Pearl Mussels were once widespread. Sadly, there are very few rivers where these marvellous mussels still live, and even fewer where baby mussels are able to grow into adults. Freshwater Pearl Mussels are now one of the most critically endangered species in the world.

Distribution and threats

Freshwater Pearl Mussels are breeding poorly because our rivers are in a poor state. Nutrient pollution from agriculture and sediment washing off land are making our rivers uninhabitable for many species. Fish numbers have fallen so baby mussels cannot survive, and mussel beds are choked with silt and algae causing the adult mussels to die. People fishing for pearls – an illegal activity – are also a concern, even though they are very unlikely to ever find a pearl in a pearl mussel.

We’re working with partners in Wales Environment Link  and the Species Champion Nick Ramsay AM to highlight the plight of the Freshwater Pearl Mussel and find ways to secure its future.