Application of a quantitative framework to estimate trawling impacts on benthic community in Central Mediterranean Sea

The Marine Strategy Framework Directive aims to protect EU marine waters by achieving good environmental status. Descriptor 6 focuses on seafloor integrity, which is threatened by activities like bottom trawling, which disturbs the seafloor, alters marine diversity, and impacts habitat functions. In this study, we assessed the impact of bottom trawling on the benthic community of the Sicilian continental shelf using three model-derived indicators based on community longevity composition: L1, proportion of the community with life spans exceeding the interval between trawling; L2, the decrease in median longevity; PD, population dynamics, decrease in biomass relative to carrying capacity. Biomass~longevity distributions were estimated using epifauna data from trawl survey in conjunction with fishing intensity and environmental variables to compute L1, L2, and PD across the study area. High-intensity trawling occurs in about 75% of the area, with the most intense activity occurring over sandy substrates and near the shelf edge. Median longevity ranged from 8 to 9 years and was generally higher at greater depths. The L1 indicator (0.67 ± 0.43) shows that in 63% of the continental shelf at least 80% of the community has a longevity greater than the interval between trawling events, and helps pinpoint minimally impacted zones that could serve as community baselines. The L2 indicator (lower average impact of 0.01 ± 0.18) suggests minimal reductions in median longevity. The PD indicator (0.16 ± 0.17) shows higher impact zones aligned with the distribution of trawling, particularly along the shelf edge and in muddy sediments. Both PD and L2 reveal significant negative impacts along the shelf edge, especially in nursery zones of European hake and deep-water rose shrimp. PD highlights zones where long-lived species are most affected, such as the eastern Adventure Bank and northwestern Malta Bank. The generated maps can represent a baseline to inform policymakers in identifying sensitive areas and then address more effective spatial planning management and control measures enforcement at a regional scale.