The Strait of Sicily is one of the most important fishing areas of the Mediterranean Sea, where significant fleets operate with high fish production. It features high habitat heterogeneity, spawning and nursery grounds for large pelagic fish, persistent hotspots of diversity of demersal species, and large fluxes exotic species. Yet, the available knowledge on fishery resources and their ecosystems in the region is often scarce.
The work done for the implementation of Atlantis for the Strait of Sicily represents the first ever attempt at:
systematically gathering data for the whole ecosystem (from bacteria to top predators and fishing fleets)
creating a E2E model for the Strait of Sicily as an Ecosystem Approach to Fisheries Management tool
describing the impact of climatic changes and capture fisheries on the ecosystem.
The bulk of the work was dedicated to the representation of the complex Strait of Sicily ecosystem structure and interaction with all compartments (biological trophic interactions, climate change, human induced pressure). This activity was dependent on the collaboration with other national partners and on an extensive data collection and transformation, integrating previously achieved data. The biological groups included in Atlantis12 were made up of functional groups and dominant target species in the Sicily Channel fisheries. The biological community was constructed using data from the MEDITS survey programme (International bottom trawl survey in the Mediterranean, MEDITS). A total of 354 species sampled were aggregated in functional groups. For each group information on their spatial distribution and movement, reproduction, migration, length-weight relationship, growth rate and mortality were gathered from different sources (assessment report, published papers, technical report, FishBase database) and used to describe their biological characteristics.
The case study area corresponds to the North sector f the Strait of Sicily and includes the FAO-GFCM geographical sub-areas (GSAs) 15 (Malta Island) and 16 (South of Sicily).
The Atlantis model domain was divided into 37 polygons, 5 of which are islands, matched to the major geographical and bioregional features of the simulated marine system. Each polygon is vertically divided in up to 5 water layers, depending on the average box depth, and 1 sediment layer. All input and output data are organised according to the model vertical and horizontal displacement of the polygons in a 37x6 grid format.
Non target species with similar size, diet, predators, habitat preferences, in particular shelf and slope areas, migratory patterns and life history strategy have been aggregated into 45 functional groups, 19 of which vertebrates, with some of the most commercially important species represented at species level, currently Aristaeomorpha foliacea, Engraulis encrasicolus, Merluccius merluccius, Mullus barbatus, Parapaeneus longirostris and Sardina pilchardus.
The fisheries fleet, which at present has not yet been implemented, will consist of 9 vessel types: bottom trawlers, pelagic trawlers, pelagic artisanal vessels, demersal artisanal vessels, purse seine, demersal longline, pelagic longline, gillnets and trammel nets.
Two scenarios have been implemented for the Strait of Sicily case study: a hindcast run of the past 10 years describing the current state of the ecosystem and a future scenario based on the AR4 SRES scenario A2, corresponding to the ELME scenarios for National Enterprise. Forcing data to the model were provided by the results of the biogeochemical model POLCOMS-ERSEM done in WP5.1. For the hindcast scenario, the model was calibrated using historical datasets from MEDITS time-series from year 2003 to 2012. Simulation runs showed that the Strait of Sicily ecosystem took about 15-20 years spin-off time before stabilising. The model was capable of capturing primary producers (phytoplankton) and secondary producers (zooplankton) and also small pelagics (sardine and anchovies), which contribute 33% to 51% of the total Mediterranean landings biomass, were reproduced to levels similar to observations for this area. The A2 scenario (2040-2050) produced similar biomass of phyto and zooplankton, with an increase in anchovies and sardine biomass. The model in its current state was run for up to 50 years, but it needs additional tuning, in particular to the benthic and demersal compartments and their trophic interactions.