Molluscan fauna in the freshwater tidal area of the River Minho estuary, NW of Iberian Peninsula

Abstract

Ten species of molluscs were identified in the freshwater tidal area of the River Minho estuary. Species richness per site ranged from 1 to 9. Abundance ranged from 230 to 4130 individuals per m2, with an average of 1412 individuals per m2. Corbicula fluminea (Müller, 1774) presented the highest density, corresponding to 88.7 % of the total specimens gathered, followed by Pisidium amnicum (Müller, 1774) with 5.8 %. Biomass ranged from 17.0 to 249.6 g AFDW m-2, with an average of 99.8 g AFDW 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 exclusively represented by C. fluminea, and another group with a more diverse assemblage.