Identifying suitable habitats under climate change for non-targeted demersal fish in the Mediterranean Sea

Non-targeted fish species contribute significantly to the structure and functioning of marine ecosystems, but they remain largely understudied. In this study, species distribution models (SDMs) were applied using the MaxEnt algorithm to assess current and future habitat suitability for 103 non-targeted species in the Mediterranean Sea. Based on trawl survey data from 2010 to 2022, and nine environmental variables, SDMs were calibrated and projected under three climate change scenarios (SSP1-1.9, SSP2-4.5, SSP5-8.5) for two future periods (2040–2050, 2090–2100). Among the environmental layers, depth, distance to the coast and sea bottom temperature explained most of the species’ distribution. Results indicate a general decline in suitable habitats for 97% of the species, particularly under the high emissions scenario SSP5-8.5 by 2100, independent of habitat type, with slightly greater declines for higher-trophic level species. Several species are projected to be at high risk of local or regional extinction. Moreover, future species distributions exhibited large spatial shifts of the centroids compared to the present-day, mainly explained by the contraction of suitable habitats rather than by expansion to new areas. Areas in the central and eastern basin of the Mediterranean Sea exhibited the highest levels of species turnover, indicating their potential higher vulnerability under climate change. These findings highlight the importance of integrating non-targeted species into conservation planning and fisheries management, as well as the need to prioritize areas that can sustain biodiversity in a rapidly changing Mediterranean ecosystem.