Freshwater pearl mussel

Two centuries ago they would have carpeted some Welsh river beds. Today, they are few and far between - drastic measures are being taken to spare the mollusc from extinction.

About 200 years ago pearl mussels were harvested for, as the name suggests, pearls. However, the name can mislead - only about one per cent of them contain this hidden 'treasure' (and most of these are dark coloured and mis-shapen).

The Environment Agency is working to tackle pollution in the rivers so that eventually the mussels can be released into the wild.

The mussels are still found in the Dee and the Wye and in nine other rain-fed rivers in Wales. They are believed to have already become extinct in several rivers including the Usk, Ogwen, Taf and Gwyrfai.

The Countryside Council for Wales, Environment Agency, Chester Zoo, North East Wales Wildlife and Denbighshire Biodiversity Partnership have been working together to save the Welsh pearl mussel populations.

In 2005 they started collecting mussels from the rivers and taking them to hatcheries to breed. So far the scheme has been successful.