Bottom trawling and environmental variables drive the biodiversity of mediterranean demersal assemblages

Marine ecosystems are healthy with a high degree of biodiversity. Assessing how factors affect spatial and temporal patterns of biodiversity is an essential task for the Ecosystem Based Management approach. In this work, we investigated the effect of fisheries disturbance and ocean variables in determining α- and β-diversity of Mediterranean demersal assemblages. Generalized additive mixed models were used to explain the spatio-temporal variability of diversity indices from 2014 to 2020 in three Mediterranean subregions as a function of covariates. An in-depth analysis also made it possible to decouple the effects of bottom trawling from the other covariates. The results show that several fishing activities and environmental variables influence biodiversity, but the direction of change depends on the subregion considered. Bottom trawling instead has a quasi-linear erosion effect on α- and β-diversity in all areas. Valuable commercial species and threatened rays and sharks importantly characterized the sites with low fishing impact. Results are a step towards the development of conservation and management strategies, particularly in the context of the Marine Strategy.