Potential vulnerability of demersal fisheries to Western Mediterranean warming

Western Mediterranean Sea is immersed in a warming process, at least since the beginning of the XX century. Moreover, climate simulations project an accelerated warming at all depths for the next decades. The effects of sea warming on demersal species of high commercial interest is an open question of paramount relevance for the management of their fisheries. Unfortunately, the answer is not simple as it involves a complex chain of interactions between environmental conditions and the different trophic levels. A first limitation is that there is no clear knowledge of the thermal limits of these species, so the direct impact of warming on the individuals cannot be assessed.

 The aim of this study is to establish the thermal limits of 24 selected demersal or benthopelagic species of fishes, crustaceans and cephalopods of commercial interest and the effects of global warming on their distributions in the Western Mediterranean. In particular, we selected Merluccius merluccius, Arsteus antennatus, Parapenaeus longirostris, Octopus vulgaris, Nephrops norvegicus, Mullus barbatus, M. surmuletus, Pagellus erythrinus, P. bogaraveo, Sepia officinalis, Solea solea, Phycis blennoides, Lophius budegassa, L. piscatorius, Illex coindetti, Eledone cirrhosa, E. moschata, Lepidorhombus boscii, Helicolenus dactylopterus, Trachurus trachurus, T. mediterraneus, Aristaeomorpha foliacea, Todarodes sagittatus and Loligo vulgaris. First, we reviewed the literature regarding temperature range where each species has been found. We also used global databases of species distribution and cross them with temperature information to characterise a conservative range of optimal temperatures for each species. Once the thermal ranges were defined, we compared them with the current projections of temperature evolution of Mediterranean waters to describe the future changes in the suitable habitat of the studied species due to ocean warming.

Our results suggest that, under a business-as-usual scenario (RCP8.5), at the end of the century 8 of 19 species will see their potential habitat greatly reduced, 3 of 19 will find a moderate reduction and 8 of 19 will not be directly affected by the warming.