On the edge: segregation and coexistence between epibenthic fish species in Mediterranean mesophotic habitats

Mediterranean coralligenous outcrops are a biodiversity hotspot where cryptobenthic and epibenthic fish species conform an important proportion of the inhabiting fish assemblages. We investigated the distribution of epibenthic fish assemblages in coralligenous outcrops, the contiguous detritic bottoms and the margin where coralligenous outcrops meet the detritic bottoms in the Columbretes Islands (NW Mediterranean Sea). Our results showed significant differences in the distribution of epibenthic fish. In terms of species diversity, the margin held the same number of species than the coralligenous. However, two species ( Gobius kolombatovici and Thorogobius macrolepis ) found their habitat almost exclusively in the margin, which was clearly dominated in terms of abundance by G. kolombatovici . On the other hand, detritic bottoms were characterized by a lower number of species. Altogether, the obtained results show the importance of coralligenous outcrops for Mediterranean epibenthic fishes and especially their margin with adjacent detritic bottoms, which holds a characteristic epibenthic fish assemblage.