The Mediterranean Sea is a hotspot of biodiversity, and global warming is expected to have a significant influence on fish species.  Here, we projected the potential future climatic niches of all Mediterranean fish species based on a global warming scenario (IPCC, scenario A2) implemented with the Mediterranean model OPAMED8 and a multi-model inference, which included uncertainty. A database was generated for the geographic distributions of fish species in the Mediterranean Sea using a Geographical Information System software package (ArcView 9.3 by ESRI). Data were compiled from the atlas of Fishes of the Northern Atlantic and Mediterranean. That atlas is based on regional data sets and expert knowledge; it provides the only available basin-wide information on the geographic ranges of all Mediterranean Sea fish species. Since there is still uncertainty in the modeling of climatic habitats that determine species geographic distributions, we implemented an ensemble forecasting method according to the most recent methodological developments.

Results/Conclusions

 By 2070-2099, the average surface temperature of the Mediterranean Sea was projected to warm by 3.1°C. Projections for 2041-2060 are that 25 endemic species would qualify for the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List, and 6 of these species would become extinct. By 2070-2099, 45 species were expected to qualify for the IUCN Red List while 14 were expected to become extinct. By the middle of the 21^st century, the coldest areas of the Mediterranean Sea (Adriatic Sea and Gulf of Lion ) would act as a refuge for cold-water species, but by the end of the century, those areas were projected to become a “cul-de-sac” that would drive those species towards extinction. In addition, the range size of endemic species was projected to undergo extensive fragmentation, which is a potentially aggravating factor. As a whole, the Mediterranean continental shelf was predicted to experience a total modification of fish assemblages by the end of the 21^st century. This expected turnover rate could be mitigated by marine protected areas or accelerated by human pressure or competition from exotic fishes. We found a spatial congruence between the areas where the highest species turnover is expected and the protected areas.