Mollusc community from a rocky intertidal zone in Acapulco, Mexico

Abstract

The state of Guerrero, Mexico, has approximately 470 km of seashore but the marine fauna is not well known. The coastline has three marine areas for priority conservation of coastal and oceanic biodiversity, for which Comisión Nacional para la Conservación y Uso de la Biodiversidad (CONABIO) notes a distinct lack of knowledge in these areas. This study was carried out in a rocky intertidal middle zone from Playa ‘Majahua’, Acapulco, located south of Bahia de Puerto Marques. The objectives were to study: the species richness for classes Gastropoda, Bivalvia and Polyplacophora; the community structure from the representation of classes, families and genera; estimate density and species composition within a community; analyse size and structure of populations in the mollusc community; and estimate the diversity index. Three samplings were made in the intertidal middle zone in 2009. Ten square metres were sampled at each visit. Ninety-nine mollusc species were found to be represented, corresponding to 36 families. From all of these species, no record in Acapulco was found for 21 Gastropoda, 5 Bivalvia and 8 Polyplacophora species recorded. Gastropoda was the best represented; 1737 organisms were analysed with an estimated density of 86.8 organisms/m2 and 31 species were dominant. Crucibullum umbrella was the largest sized species. The diversity and equity index estimate in Majahua was the highest found for the rocky coast of Guerrero, indicating a mega-diverse area with great uniformity.