This study has been funded by the Spanish Ministry of Economy and Competitiveness, Grant CGL-2013-42415-R and the Principality of Asturias (Spain), Grant GRUPIN-2014-093. This is a contribution from the Marine Observatory of Asturias (OMA). Alba Ardura is recipient of a Postdoctoral Fellowship with reference Clarin-COFUND-PCTI-FICYT. Laura Clusa holds a PCTI Grant from the Asturias Regional Government, referenced BP14-145. We are grateful to an anonymous Reviewer who kindly helped to improve this manuscript.