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An important part of the fishing activity in Mexico is carried out in the coastal strip and has a strong social, economic and ecological importance. In the state of Guerrero, mollusks fishing is coastal and craftwork activity focused on a small number of species and without information on biology and reproductive or ecological aspects for most species caught. This research was carried out in the Costa Chica region, Guerrero, Mexico and the aims were: 1) To analyze the socioeconomic features of cooperative societies of fishing production; and 2) To know the diversity of mollusks caught by coastal fishing and the species that have the greatest importance in fishing. From February to April 2013-2015, seven fish coop units, four piers and places where seafood is sold were visited. For the socioeconomic analysis and the determination of the species that have more importance in the coastal fishing, a total of 67 surveys were applied. In order to determine the cast of species, the specimens captured by the fishermen were used, which were identified and counted. A total of 67 interviews were analyzed and an average of $1806.00 was estimated as weekly economic income just as a product of fishing, it was also estimated that on average the fishermen work 4.3 days a week. Fisheries cooperatives market most of their produce directly to restaurateurs and locals on the piers. Replacement of older adults by young fishermen from the same region was observed, most are adults between 22 and 39 years old. 25 species of mollusks of economic importance were registered for the coastal fishermen of the Costa

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Riqueza, composición y diversidad de la comunidad de moluscos asociada al sustrato rocoso intermareal de playa Parque de la Reina, Acapulco, México Abstract.-The information available about marine biodiversity in the State of Guerrero, Mexico, is scarce as designated by the National Commission for the Conservation and Use of Biodiversity. To gain on this issue, this work was carried on at the rocky intertidal zone of Parque de la Reina beach, Acapulco, which is located in the Priority Region for Marine Conservation and Biodiversity Use Number 32. The objective was to establish the mollusks species richness, community structure, determine the density and degree of species occurrence, composition by size and diversity. The sampling area was 10 m -2 and the sampling unit was 1 m -2 . Fifty eight species were identified, with 4 new records for the intertidal rocky shores of Acapulco. The best represented families were: Muricidae, Ischnochitonidae, and Mytilidae. The observed density was of 207.55 m -2 . Twenty one species were rated as dominant. Macrocypraea cervinetta had the highest size. The mollusks richness was high, as is expected in the tropics. The constant and dominant species accounted for 55.16% of the total, and considered as representative of the community. The density found was higher than has been previously reported for the State of Guerrero; the type of substrate is one of the determining factors defining species richness and abundance. Key words: Check list, degree of occurrence, dominance, size and recordsResumen.-El conocimiento de la biodiversidad marina en el Estado de Guerrero, México es escaso, lo que es señalado por la Comisión Nacional para la Conservación y Uso de la Biodiversidad. Para avanzar en este conocimiento, se trabajó en el intermareal rocoso de Playa Parque de la Reina, Acapulco, que se encuentra ubicada en la región marina prioritaria para la conservación y uso de la biodiversidad número 32. El objetivo fue determinar la riqueza de especies de moluscos, conocer la composición de la comunidad, la densidad, el grado de aparición de las especies, la composición por tallas y la diversidad. El área de muestreo fue de 10 m -2 y la unidad de muestreo fue 1 m -2 . Se identificaron 58 especies, 4 nuevos registros para el intermareal rocoso de Acapulco. Las familias más representadas fueron: Muricidae, Ischnochitonidae, y Mytilidae. La densidad fue de 207,55 organismos m -2 . Fueron dominantes 21 especies. Macrocypraea cervinetta presentó la mayor talla. La riqueza de moluscos fue alta, coincidiendo con lo esperado en una zona tropical. Las especies dominantes y constantes representaron el 55,16%, y se consideran representativas de la comunidad. La densidad encontrada es la más alta que se ha reportado para Guerrero, México y el tipo de sustrato es uno de los factores determinantes que define la riqueza de especies y la abundancia.

The coast of Acapulco is located within the Marine Priority Region No. 32 (MPR No. 32) at the State of Guerrero, Mexico. The National Commission for the Knowledge and Use of Biodiversity has stated the lack of information on marine species that live there, among which are the Class Polyplacophora. This study aimed to: 1) determine species richness, 2) the community structure based on the representative families, 3) estimate the density, 4) locate species distribution, 5) determine their degree of occurrence (hierarchical position) within the community, 6) analyze the structure of length and width across the populations and 7) estimate the diversity index. The intertidal rocky substrate at seven beaches was sampled from 2009 to 2012. The sampling unit 1 m², while the area sampled was 10 m². It was analyzed 2.548 specimens of Polyplacophora, with 20 species identified. Tonicellidae and Ischnochitonidae were the Families better represented inspecies richness and Chitonidae in abundance. Lepidochitona flectens is a new record for the <i>Mexican Tropical Pacific</i> and <i>Stenoplax mariposa</i> for MPR. No. 32. The density was 25.48 specimens/m2. Eight dominant species were determined. Chiton albolineatus had the highest density. <i>Ischnochiton muscarius, Chaetopleura unilineata, Chiton albolineatus and Chiton articulatus</i> presented wide distribution. <i>Chiton articulatus</i> showed the largest size in length and width. H’ = 2.01 bits/ individual. Numerous dominant species were present with broad and regular distribution, probably due to Polyplacophora body design, which allows for better adaptation to the rigorous environmental conditions of the rocky intertidal