Polygon dataset illustrating Pearl Mussel catchment areas within Ireland.

Reccomended viewing, http://www.npws.ie/en/media/Media,6124,en.pdf

The freshwater pearl mussel, scientific name Margaritifera margaritifera, is an endangered species of freshwater mussel, an aquatic bivalve mollusk in the family Margaritiferidae, the freshwater pearl mussels. Margaritifera margaritifera durrovensis. is a critically endangered subspecies in Ireland. Synonym: Margaritifera durrovensis. This subspecies is mentioned in annexes II and V of Habitats Directive as Margaritifera durrovensis.

The name "freshwater pearl mussel" should not be construed to mean that other freshwater mussels do not harbor pearls or cannot be used as mother of pearl. In fact most cultured pearls today come from Hyriopsis species in Asia, or Amblema species in North America, both members of the related family Unionidae. Pearls are also found in genus unio.

The interior of the shell of this species has thick nacre. The species is capable of making fine quality pearls, therefore it was historically exploited in the search for pearls from wild sources.