The taxonomic composition, density and the spatial distribution of benthic molluscs in low Tietê, São Paulo reservoirs were analyzed in November 2002 and August 2003. The exotic species Melanoides tuberculata was distributed in all portions sampled and was the most abundant species, corresponding to 65.9% or more of the total abundance, being dominant in all reservoirs, with a maximum density of 23,753 ind.m-2 recorded in the depth of 2 m, at the superior portion of Nova Avanhandava reservoir.The other exotic species, Corbicula fluminea and Helisoma sp., were much less abundant and they were not registered in all portions of the reservoirs. The native species were Aylacostoma tenuilabris, Biomphalaria glabrata, B. intermedia, Physa cubensis and Pomacea canaliculata. These species contributed with less than 20% of the total abundance of molluscs in the reservoirs, occurring in low densities, much inferior to those of the exotic species, mainly regarding M. tuberculata, possibly indicating the impact of the exotic invader species on the native populations.
Corbicula fluminea; malacofauna; Melanoides tuberculata; Southeast Brazil
