Tamiahua Lagoon, located on the east coast of Mexico, has an area of 800 km super(2). The lagoon receives a flow of fish recruits from the Gulf of Mexico, of which several are important from a fisheries and ecological point of view. The trophic relations and their importance in the structure of the lagoon community were quantified by means of an ECOPATH II model. The results show that the lagoon imports detritus from adjacent systems, and uses it to sustain the benthos community which is the food base for almost all of the fish. Therefore, the trophic chains in the lagoon tend to be short, and there are no third-order predators.