Spatiotemporal fishing effort simulations and restriction scenarios in Thermaikos Gulf, Greece (northeastern Mediterranean Sea)

Spatiotemporal simulation modeling is used in the context of ecosystem-based fisheries management to investigate different management options, including the size and allocation of marine protected and fisheries restricted areas. Here, we used ECOSPACE to assess the effectiveness of existing and potential future spatiotemporal fishing restrictions in the heavily exploited Thermaikos Gulf, Greece for the years 2000-2025 (calibration period 2000-2016; projection period 2017-2025). ECOSPACE combines temporal biomass and commercial catch data with spatial habitat and other environmental data, as well as species ecological preferences, feeding, and dispersal rates to depict changes in trophic interactions, biomasses, and commercial catches in time and space. ECOSPACE simulations supported the empirical data demonstrating that fisheries restricted areas are effective tools for rebuilding the biomass of exploited stocks, with their size and location playing a significant role in the way that different organisms respond to protection. Nevertheless, our results suggested that in order to achieve the highest benefits of protection, fisheries restricted areas would need to be accompanied by a parallel reduction in total fishing effort, rather than a redistribution of fishing activities. Such redistribution would just move the pressure on the boundaries of protected areas, causing a local increase of commercial catches owing to the beneficial spillover effects of protection. One of the tested spatiotemporal restriction scenarios (MPA 5) suggests certain additional management measures on top of the existing restrictions for all four fishing fleets operating in the area. This scenario predicted a considerable increase in the biomass of key commercial and vulnerable species groups, including hake, flatfishes, anglerfish, sharks, and rays and skates, by the end of the simulation period in 2025.