Mapping vulnerable marine ecosystems to support conservation measures for Isidella elongata in the Southern Adriatic...

The protection of Vulnerable Marine Ecosystems (VMEs) is a priority for ecosystem-based fisheries management in the Mediterranean Sea. The bamboo coral Isidella elongata forms complex habitats that are extremely sensitive to bottom trawling. This study investigates its occurrence, spatial distribution, and biomass in the Southern Adriatic Sea (GSA 18), providing scientific support for the final delineation of the Fisheries Restricted Area (FRA) in the Otranto Channel within the framework of the General Fisheries Commission for the Mediterranean, building upon the initial FRA proposal put forward in 2019. Data from MEDITS trawl surveys and Remotely Operated Vehicle observations were integrated with environmental variables and fishing effort estimated from Automatic Identification System and Vessel Monitoring System data. Habitat suitability was modelled using Maximum Entropy, while biomass distribution was estimated through Generalized Additive Models. Depth, particularly between 500 and 650 m, seafloor slope, and fishing pressure emerged as the primary drivers of distribution patterns. Results showed strong agreement between predicted suitable habitats and biomass hotspots, as well as an inverse relationship between fishing effort and coral biomass. Areas with high suitability but low biomass were identified as potentially degraded. These findings provided spatially explicit support for FRA design and demonstrated the value of integrated modelling approaches for the conservation of deep-sea VMEs in the Mediterranean Sea.