All of the larger mussel species, Anodonta, Unio and Margaritifera are all able to move around the surface of their habitats and burrow. They have a large foot which fills with blood to enable this movement. This time lapse video of pearl mussels placed in a flume illustrates this brilliantly (Freshwater Biological Association).

Pearl mussels are endangered. Westcountry Rivers Trust has joined forces with Devon Wildlife Trust (local lead partner), North Devon Biosphere Service, Tarka Country Trust and the Environment Agency to protect and restore freshwater pearl mussel populations in the South West of England.  This is part of a larger national project led by the Freshwater Biological Association in Cumbria and funded by the landfill tax from Biffa Award.

Freshwater pearl mussels are a keystone species, providing a vital environmental service through their filtering activity in the water and presenting as an informal indicator species through their sensitivity.  The species are susceptible to environmental change, being sensitive to sedimentation and eutrophication.  The main cause of decline of this species is poor habitat quality caused by a number of factors including intensive land use practices within a catchment.