A food-web model as a tool for the ecosystem-level management of bivalves in an Atlantic coastal lagoon

Abstract

The Ria de Aveiro is an important coastal lagoon for wildlife in Portugal, where the production of bivalves reaches approximately 2700 tonnes annually. However, the illegal overfishing of bivalves is frequent in this lagoon, which causes critical changes in the ecosystem. In this study, using a developed food-web model (Ecopath model), the ecological carrying capacity and maximum sustained yield of bivalve filter feeders were estimated, and further increases in bivalve biomass in other species groups were investigated. The results showed that 1) the current biomass and legal catch of bivalves do not yet exceed the ecological carrying capacity (177.84 tonnes km− 2) or the maximum sustained yield (88.92 tonnes km− 2 year− 1) in Ria de Averio; 2) the harvested bivalves of the maximum sustained yield represent removing from the ecosystem ~ 581 tonnes carbon (C) and ~ 83 tonnes nitrogen (N) annually, with substantial ecological and economic implications; and 3) a further increase in the biomass levels of bivalves may cause the ecotrophic efficiency of other groups to become unrealistic, potentially leading to decreases in ecosystem transfer efficiency, biodiversity and health. The results here are expected to guide the sustainable development and management of bivalves in Ria de Averio and the protection of the local environment.