ISOTOPIC CHARACTERIZATION (DELTA-C-13) OF THE CRAB FAUNA IN THE ALVARADO LAGOON SYSTEM, VERACRUZ, MEXICO

Isotopic (deltaC-13) analyses of estuarine fauna give an indication of the diet of organisms and the flow of carbon throughout trophic chain s, and allow the establishment of relationships between community comp onents. Values of - 17.4 to -25.2 parts per thousand were obtained for penaeid and caridean shrimps and for swimming crabs collected in the lagoon system of Alvarado, Mexico. These values establish an isotopic gradient from the southeast of the system (-25.0 to -26.9 parts per th ousand) to Laguna Camaronera in the northwest (-18.3 to -19.4 parts pe r thousand) which, in the case of Penaeus setiferus, P. aztecus and Ca llinectes sapidus, points to a migration of organisms within the syste m. These three species also represent the highest trophic level in the macrocrustacean communities throughout the system.