Ten species of molluscs were identified in the freshwater tidal area of the River Minho estuary. Species richness per site rangedfrom 1 to 9. Abundance ranged from 230 to 4130 individuals per m², with an average of 1412 individuals per m2. Corbiculafluminea(Müller, 1774) presented the highest density, corresponding to 88.7 % of the total specimens gathered, followed byPisidium amnicum (Müller, 1774) with 5.8 %. Biomass ranged from 17.0 to 249.6 g AFDW m-2, with an average of 99.8 gAFDW m-2. C. fluminea was the species dominating the total biomass (95.4 %), followed by Bithynia tentaculata (Linnaeus,1758) with 1.6 %. A multivariate analysis revealed a community with two distinct groups : one group almost or exclusivelyrepresented by C. fluminea, and another group with a more diverse assemblage.
