In the present study discussed the influence of institutional arrangements in the use and state of the resource piangua (Anadara similis and Anadara tuberculosa) in two villages of the Consejo Comunitario de Bahia Malaga La Plata, during the months of July and August 2013. Work of social mapping was performed to identify areas of use, as well as workshops and interviews to understand the perception of change in resources over time, focusing in the existence of both formal rules and informal that has influenced the management of resources. Records of daily catches and measures of 1868 individuals of piangua were registered and annual records were used to plot the pattern of resource. We identified 92 extraction areas of which 66 are used with different intensities. It was found that the distance is an important factor for the activity, in which most people prefer to use the closer areas to the village. The average catch size for species found is above the average size of sexual maturity, but below the national minimum size of capture. The annual records showed an increasing trend in marketing for A. tuberculosa. It was determined that institutional arrangements positively influence the state of resource, although the dynamics of marketing is affecting the implementation of the rules due to the current commercial use. Special attention needs to be focused on local buyers and brokers and the current trend of the resource.