Mollusks occupy different kinds of environments, including the intertidal zone. The present study investigated the spatial distribution of mollusks on beach rocks of the intertidal zone of Pacheco Beach in the state of Ceará, Brazil. Sampling occurred from August 2006 to September 2007. Across two transects, six samples of 0.25 m² were collected monthly in gaps of 30 m (0 m, 30 m, 60 m, 90 m, 120 m and 150 m). The mollusks were counted in field, and samples of sediment and algae were taken for further analysis. A total of 74,515 individuals were found and classified into 67 species, 52 genera and 39 families. Gastropods were predominant, corresponding to 73.1% of the species, followed by bivalves (22.4%) and chitons (4.5%). Caecum ryssotitum de Folin, 1867 was the most abundant taxon, representing 68.8% of total specimen findings. In general, species were mostly found in Middle Littoral zone (samples 60 m and 90 m), suggesting that the greater number of microenvironments available in this area may contribute to establishment and survival.
Beach rocks; malacofauna; Middle Littoral zone
