Modelling ecosystem structure and function of Saros Bay (North Aegean Sea)

Saros Bay has been a region closed to trawl fishing since 1991 and has also been declared a Special Environmental Protection Area since 2010. Given both cases, Saros Bay is under hunting pressure from small-scale fishing and seine fishing. Therefore, in this study, which was conducted to determine the structural and functional characteristics of the ecosystem of the region, the ecosystem model was examined using the Ecopath with Ecosim program for the period of September 2006 - September 2008. Functional groups when establishing the model; The rates of exploitation of species in terms of fisheries were created by considering their ecological niche and habitats, and the flow of energy between these functional groups was determined. The pedigree value of the installed model is 0.59, which is similar to the pedigree values of other Ecopath models made in the Mediterranean Sea. As a result of the study, In the Saros Bay ecosystem, dolphins from marine mammals were found to be involved in energy flow with the highest trophic level (TL= 4.39) and Polychaeta with the lowest level (TL= 2.11). The transfer efficiency between the trophic levels of the system is 12.6%. The ratio of total net primary production to total net respiration is 1.82, and with this value, it is seen that the region is a developing ecosystem. The average trophic level of the prey is 3.4, and the total amount of biomass of the system is 1535.24 t.km-2 .year-1 . Although the key species activity of zooplankton and small pelagic fish in the Saros Bay ecosystem is higher than other groups, a key group for full ecosystem balance has not emerged in the region. Fishing pressure on predatory species with high trophic levels such as sharks in the bay is high. This model, which was established for the period 2006-2008, creates a basis that will allow to test the operability of fishery management decisions such as the ban on trawl fishing with new models that will be created using current data reflecting the ecosystem of the region in today's conditions. Keywords: Trophic interaction, Mass-balance modelling, Ecopath, Saros Bay, Aegean Sea