Potential impacts of bottom trawling on species of skates (Rajiformes: Rajidae): the case of the Gulf of Cadiz and the Western Mediterranean

Chondrichthyans such as sharks, rays and chimaeras are highly vulnerable to fishing pressures due to their life history traits. However, there is still little knowledge surrounding the impact of fishing on species of skate in the Mediterranean Sea and the Atlantic Ocean. Using data from historical records, landings and vulnerability of the species, this study analyses the potential impact of trawling on species of skate in two areas: the western Mediterranean (Alboran Sea) and the Gulf of Cadiz. Results show that trawling mainly affects one species in the western Mediterranean, the starry ray (Raja asterias). In the Gulf of Cadiz, the three skate species that are mainly affected are the thornback ray (Raja clavata), the starry ray (R. asterias) and the undulate skate (R. undulata), but also five other species were caught in the same area, Leucoraja naveus, L. circularis, Raja brachyura, R. miraletus and R. montagui. Vulnerability assessment of the species indicate that all skate species, except Raja asterias, R. miraletus and R. montagui, achieve high vulnerability index (i.e. IV > 60) and all (except R miraletus and R. montagui) are classified in the IUCN Red List as near threatened or endangered species. Based on the results, this study proposes recommendations for measures to protect skates from trawling in these areas.