Preliminary Ecopath model of a tropical coastal estuarine ecosystem around bight of Benin, Nigeria

Abstract

The tropical coastal estuarine ecosystem around Bight of Benin, Nigeria has huge economic importance with limited information on its status and possible impact of fishing. An Ecopath model was constructed to study the trophic interactions and ecosystem properties of the estuary using fourteen functional groups. The model input parameters were gathered from published reports and catch assessment survey. Using network analysis, the system network was mapped into a linear food chain, and five discrete trophic levels were found with a mean transfer efficiency of 7.0 % from detritus and 6.1 % from primary producer. The mixed trophic impact routine showed that functional groups in lower trophic levels had smattering positive and negative impacts across the food web. The ecosystem indices: total primary productivity to total respiration ratio (6.325), total primary productivity to total biomass ratio (82.621), Finn’s cycling index (1.70), mean path length (2.298), connectance index (0.327), system omnivory index (0.288), ascendency (42.3 %) and overhead (57.7 %) showed that the estuarine ecosystem was at the developing stage, stable, susceptible to stress induced changes and could withstand unexpected external perturbation at its present stage.