Better water quality helping save the Freshwater Pearl Mussel

Improved water quality in a river shows that a £3.5 million project to safeguard Freshwater Pearl Mussels is having a positive impact.

Natural Resources Wales (NRW) is working in Snowdonia to help safeguard the rare mussel as part of a UK-wide project.

Over the last hundred years numbers of Freshwater Pearl Mussels have fallen dramatically.

Pearl Mussels:  Source NRW


They are now one of the most critically endangered molluscs in the world and as a result are highly protected under national and international legislation.

In a bid to change the mussels’ fortunes, Pearls in Peril (PIP) a Life + Nature conservation project is constructing wetland, settlement ponds, fencing the riverbanks to stop livestock entering the river and reducing pollution.

Water samples now show that the amount of oxygen in the river is improving and that there is less silt in it.

The work is taking place in 21 Special Areas of Conservation (SAC) across the UK.


NRW project officer, Elain Gwilym, is leading the project at Afon Eden near Trawsfynydd.  She explained:

“Good water quality is essential for the mussels which can live for well over 100 years.

“The figures show that the project is heading in the right direction.

“Our sampling shows that the level of oxygen in the gravel – where it’s needed for the mussels – isimproving.

“This shows that the river is cleaner, there’s less silt and more oxygen. This will improve the habitat for young pearl mussels and fish.”

The mussel colony in the river was discovered in 1997.

Then it supported around 1,300 mussels, but by 2011 this number had fallen to between 500 and 600.

Elain Gwilym added:

“Amazingly a single adult mussel can filter 50 litres of water a day, which is about the same amount we use while having a shower.

“By filtering the water the mussels remove particles for food and improve the water quality and river ecosystem for other species.

“So work to conserve Freshwater Pearl Mussels will ultimately benefit the river ecosystem as a whole.”

A vital part of the project is working with the community and landowners.

Part of this includes the “Pearls in the Classroom,” educational programme for local school children which explains the mussels unusual lifecycle, its importance in our cultural history, its decline and role in the river ecosystems.

Freshwater Pearl Mussels are known to have inhabited Welsh rivers since Roman times.

It’s believed that pearls are one of the reasons why Julius Cesar invaded Britain in 55BC and pearls have even been part of the Royal Family’s coronation regalia.

Source:  National Resources Wales (NRW) 9th December 2015