Acknowledgements
We wish to thank all the participants of the GBYP biological sampling program, in particular Naiara Serrano, Xiker Salaberria and Inma Martín for tissue sample handling and storage, Iraide Artetxe-Arrate and Ai Kimoto for database management and Iñaki Mendibil and Elisabete Bilbao for excellent laboratory work. We also would like to thank Marty Kardos for his valuable comments, contributing to the quality improvement of this manuscript. This study has been carried out under the provision of the ICCAT Atlantic Wide Research Program for Bluefin Tuna (GBYP), funded by the European Community (Grant SI2/542789), Canada, Croatia, Japan, Norway, Turkey, United States (NMFS NA11NMF4720107), Chinese Taipei, and the ICCAT Secretariat. This work was also supported by a grant (project GENGES) and a predoctoral fellowship to ND-A, from the Department of Agriculture and Fisheries of the Basque Government. The contents of the paper do not necessarily reflect the point of view of ICCAT or of the other funders. This manuscript is contribution number X [to be added upon acceptance] from the Marine Research Division of AZTI.