Title: Unidirectional trans-Atlantic gene flow and a mixed spawning area shape the genetic connectivity of Atlantic bluefin tuna

Running title: Genetic connectivity of Atlantic bluefin tuna

Natalia Díaz-Arce^1*, Pierre-Alexandre Gagnaire², David E. Richardson³, John F. Walter III⁴, Sophie Arnaud-Haond⁵, Jean-Marc Fromentin⁵, Deirdre Brophy⁶, Molly Lutcavage⁷, Piero Addis⁸, Francisco Alemany⁹, Robert Allman¹⁰, Simeon Deguara¹¹, Igaratza Fraile¹², Nicolas Goñi^12#, Alex R Hanke¹³, F Saadet Karakulak¹⁴, Ashley Pacicco¹⁵, Joseph M Quattro¹⁶, Jay R Rooker¹⁷, Haritz Arrizabalaga¹² and Naiara Rodríguez-Ezpeleta^1,*

*Correspondence: ndiaz@azti.es;nrodriguez@azti.es;

¹ AZTI Marine Research Division, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain

² ISEM, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France

³ Northeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), Narragansett, RI, USA

⁴ Southeast Fisheries Sciences Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), Miami, FL, USA

⁵ MARBEC, Univ Montpellier, Ifremer, IRD, CNRS, Sète, France

⁶ Marine and Freshwater Research Center, Atlantic Technological University (ATU), Galway City, Ireland

⁷ Large Pelagics Research Center, School for the Environment, University of Massachusetts Boston, Gloucester, MA, USA

⁸ Department of Environmental and Life Science, University of Cagliari, Cagliari, Italy

⁹ International Commission for the Conservation of Atlantic Tunas, GBYP, Madrid, Spain

¹⁰ National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, FL, USA.

¹¹ AquaBio Tech Ltd., Central Complex, Mosta, Malta

¹² AZTI Marine Research Division, Basque Research and Technology Alliance (BRTA), Pasaia, Spain

¹³ St Andrews Biological Station, Fisheries and Oceans Canada, St. Andrews, New Brunswick, Canada

¹⁴ Faculty of Aquatic Sciences, Istanbul University, Istanbul, Turkey

¹⁵ Cooperative Institute for Marine and Atmospheric Studies Rosenstiel School of Marine, Atmospheric and Earth Science, University of Miami, Miami, FL, USA

¹⁶ Department of Biological Sciences, University of South Carolina, Columbia, SC, USA

¹⁷ Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, USA

^# Present address: Fisheries and Fish Resources, Natural Resources Institute Finland, Turku, Finland