Modelling and assessing the ecosystem of the Aegean Sea, a major hub of the eastern Mediterranean at the intersection of Europe and Asia

The aim of the present work is to present the structure of a mass balanced Ecopath model in the Aegean Sea, a highly exploited ecosystem located in the eastern Mediterranean Sea, between Greece and Turkey. The model represents the yearly average between 2003 and 2006 and includes 44 functional groups. The Aegean Sea is an overall oligotrophic system, but its northern part is the most productive area in the eastern Mediterranean Sea. Results showcased a decrease in biomass and flows with increasing trophic level, in line with the PREBAL routine and other models in the basin. Demersal species played an important role in the Aegean Sea model functioning, with squids being a true keystone group, followed by European hake. Trophic flows indicated a relatively large ecosystem, close to maturity, sharing many similarities with other Mediterranean systems. Primary production required to sustain fisheries was relatively low, while gross efficiency indicated that fisheries catches in the Aegean Sea convert less effectively the primary production. The baseline model was further expanded with the ECOIND plug-in, extracting valuable information for the ecosystem state and highlighting the importance of demersal and benthic fish and invertebrate species in the ecosystem. This model will serve as the base for the development of temporal and spatial simulations that take into account the impact of fisheries and environmental changes on the ecosystem and that can be used to explore various management scenarios.