Hindawi Publishing Corporation Journal of Marine Biology Volume 2009, Article ID 176801, 12 pages doi:10.1155/2009/176801 Research Article Bivalves and Gastropods of the Gulf of Tehuantepec, Mexico: A Checklist of Species with Notes on Their Habitat and Local Distribution Eduardo R´ ıos-Jara, Ceciel-M. Navarro-Caravantes, Cristian-M. Galv´ an-Villa, and Ernesto Lopez-Uriarte Laboratorio de Ecosistemas Marinos y Acuicultura, Departamento de Ecolog´ ıa, Centro Universitario de Ciencias Biol´ ogicas y Agropecuarias, Universidad de Guadalajara, Carretera a Nogales Km. 15.5, Las Agujas Nextipac, Zapopan, Jalisco 45110, Mexico Correspondence should be addressed to Eduardo R´ ıos-Jara, edurios@cucba.udg.mx Received 1 April 2009; Accepted 19 October 2009 Recommended by Ricardo Serr˜ ao Santos The taxonomic composition of 160 species of bivalves and gastropods recorded in the Gulf of Tehuantepec is presented with information on their habitat and distribution along 10 different localities of the shoreline and 42 stations of the continental shelf. The species were on sandy and rocky beaches, coastal lagoons, estuaries, mangroves, rocky breakwaters of ports, and shallow subtidal areas (14–47 m depth). A total of 78 bivalve species and 82 gastropod species were recorded. Most of these were associated with sandy and rocky beaches and breakwaters of ports. The estuaries host 30 species and the coastal lagoons only two. In the shallow subtidal there were 18 gastropod species and 40 bivalve species representing 36.3% of all. This study adds 24 bivalve species and 29 gastropod species not recorded in previous studies for a total count of 213 species (102 bivalves and 111 gastropods) for Gulf of Tehuantepec. Copyright © 2009 Eduardo R´ ıos-Jara et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Introduction The tropical coastal environments are the most biologically diverse of all marine ecosystems but are being degraded worldwide by human activities potentially leading to numer- ous extinctions. Conservation efforts targeted toward them could help averting the loss of tropical biodiversity. However, the sustainable use of coastal living resources cannot be properly established without an adequate knowledge of the biodiversity. The molluscs are among the most diverse invertebrates in the coastal tropical environments and the vast majority are found intertidally, in estuaries and coastal lagoons, and in the shallow areas on the continental shelf [1, 2]. The first complete inventory of the subtropical and trop- ical malacological fauna of the western America is the huge monograph of Keen [3] which comprises approximately 3340 mollusc species, most of them bivalves and gastropods. Other catalogues also include the species of molluscs from the Mexican Pacific [4–6] and the revisions of the species from the Panamic Province made by Skoglund [7, 8] provide updated information including new species, redefinitions of taxonomic relationships, new records, and their geographic distributions. However, most of the literature on the mol- luscs from the Mexican Pacific refers to benthic communities of the Gulf of California [2, 9–16]. The molluscan fauna of the southernmost region of the Tropical Mexican Pacific has received little attention. The first inventories of molluscs from the Gulf of Tehuantepec were performed in the 1980s. Most of this research is included in not easily accessible technical reports and theses [17–19] or refers to specific localities and environments of the coast of Oaxaca [20, 21]. More complete lists of species from this region are found in two different catalogues, one for the coast of Oaxaca, mainly from rocky and sandy beaches and from shallow subtidal areas as far as 39 m depth [22], and another one for the coast of Chiapas, collected in 10 different shoreline locations [23].