Ecopath modelling Unravels the food web of the Gulf of Corinth, a deep Mediterranean important marine Mammal area

Abstract

The Mediterranean Sea, recognized as a biodiversity hotspot, is facing significant impacts from human-induced stressors such as overfishing and climate change, which exert pressure on its ecosystems. The Gulf of Corinth (eastern Mediterranean Sea, Greece) encompasses a deep ecosystem that has not been extensively studied, despite its rich biodiversity and the presence of Protected, Endangered, and Threatened (PET) species. An Ecopath trophic model was implemented for the baseline period 2014–2016 to outline its ecological structure, with special emphasis on (i) dolphins (bottlenose, striped, and common) and other PET species, as the Gulf is an Important Marine Mammal Area; (ii) deep-living groups such as mesopelagic fishes, due to their wide distribution and high abundance; and (iii) commercial species to assess the impact of fishing. Model outputs reveal a complex food web structure with numerous links among functional groups, with detritus serving as dominating energy source, particularly in the pelagic zone. Dominant species, such as mesozooplankton, and keystone species, including squid, sharks, and hake, shape the trophic relationships in the water column, with keystone prey groups such as shrimps and mesopelagic fish contributing significantly. Model statistics align with those of other modeled ecosystems in Greece, consistent with productivity patterns and other ecological features; however, ecological indicators suggest a relatively immature ecosystem state despite low fishing pressure. Due to spatio-temporal bans on semi-industrial fisheries and the absence of extensive suitable trawling grounds and small pelagic fish populations, small-scale fisheries exert the highest fishing pressure. The estimated probability of sustainable fisheries in the ecosystem is high (estimated at 94%), while trophic competition among fisheries and PET species is moderate to low, with the exception of bottlenose dolphins. The model was developed to enhance understanding of species trophic relationships and energy flows in the system, making it a critical tool for effective management and conservation initiatives in the Gulf of Corinth.