Aplicação de modelos tróficos em um estuário tropical : um estudo de caso em Pernambuco

Abstract

The ecosystem approach Ecopath with Ecosim was used to describe the food web structure, and to evaluate the fishing effects in a tropical estuary ecosystem in northeastern Brazil (Estuary of the Sirinhaém River – SRE). To build the Ecopath model we sampled fish species and macroinvertebrates between 2013-2014, while data of primary production and zooplankton were obtained from literature. Results showed that the energy transfer in the SRE food web was based mostly on grazing food chain (60.5%), with an average transfer efficiency of 6.79%, relatively low compared to the theoretical value of 10%, indicating low global transfer efficiency, although it is within the range reported in various estuarine trophic models. The keystone index together with the MTI (Mixed Trophic Impact) index indicated the snook (Centropomus spp.), with Trophic Level = 3.20, as a key component in the system, which could trigger a cascade effect (top-down). The increasing in the fishery activity causes a reduction in the Snook biomass, and consequently decrease the pressure of predation on their prey. The ecological indicators of ecosystem health indicated that the SRE is a system in development, as most estuaries, requiring management strategies to the maintenance for the equilibrium state.This study provides the first information to describe and evaluate the state of food web in a tropical estuarine ecosystem in Northeast Brazil.