The freshwater pearl mussel [Margaritifera margaritifera (L.)] (Bivalvia, Unionoida) rediscovered in Portugal and threats to its survival

The freshwater pearl mussel (Margaritifera margaritifera) was discovered in six rivers in Portugal, where it had been considered extinct, these being the southernmost European populations, together with the river Agueda in Spain. The former distribution of the mussel in Portugal included suitable habitats in river basins located north and including the Vouga river basin. A severe decline, caused by pollution and river channel alteration, seems evident. The populations in rivers Cavado, Neiva and Paiva are small and with no evidence of recent recruitment. In the rivers Mente, Rabacal and Tuela large populations were found, with evidence of juvenile recruitment. They are extremely important for the conservation of the species in the south of its European distribution, but are also threatened, especially in rivers Mente and Rabacal affected by two dams to be constructed in the very near future. The conservation of the mussel in Portugal depends on extensive surveys of their actual populations and efforts for protecting them. If this is achieved, Portuguese and Spanish populations of M. margaritifera together could be a stronghold for the conservation of the species in Europe. (C) 2003 Elsevier Ltd. All rights reserved.