A food-web comparative modeling approach highlights ecosystem singularities of the Gulf of Alicante (Western Mediterranean Sea)

Abstract

A food-web comparative modeling approach using Ecopath with Ecosim (EwE) was built to characterize the ecosystem of the Gulf of Alicante (GoA) and investigate its singularities. The GoA differs from neighboring ecosystems of the Western Mediterranean Sea because of its different oceanographic characteristics. We developed a model of the study area representing early 2010s, covering a total area of 7085 km2, and including the continental shelf and upper slope with depths from 50 to 800 m. In total, 45 functional groups considering all components of the food web (fish, marine mammals, seabirds, invertebrates, primary producers, and detritus) were selected to build the ecological model. The fishery was represented by the four main fleets operating in the area (i.e., bottom trawl, purse seine, longlines, and small-scale fisheries) and we included official landing data and estimated percentage of discarded species. Results were then compared with available outputs of available models representing adjacent ecosystems such as the Gulf of Cadiz (in the Atlantic side) and the North Western Mediterranean Sea (north of the study area). The study revealed that the major differences found between models were due to the lower primary production in the GoA. This led to lower catches and higher importance of the demersal compartment, where the most biomass was associated to the detritus. The main trophic flows in the GoA were originated at the basis of the food web, likely related to bottom-up flow control. Interactions between pelagic and demersal groups were weaker than in neighboring areas. Despite the high values of ecotrophic efficiencies and mortality rates, results showed a lower fishing pressure than in neighboring areas, suggesting a moderate exploitation level of marine resources in the GoA. This study fills a knowledge gap in the area and sets the baseline to develop future studies to test scenarios of change and management options.