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Díaz-Arce N, Gagnaire PA, Richardson DE, Walter JF, Arnaud-Haond S, Fromentin JM, Brophy D, Lutcavage M, Addis P, Alemany F, Allman R, Deguara S, Fraile I, Goñi N, Hanke AR, Karakulak FS, Pacicco A, Quattro JM, Rooker JR, Arrizabalaga H, Rodríguez-Ezpeleta N. Unidirectional trans-Atlantic gene flow and a mixed spawning area shape the genetic connectivity of Atlantic bluefin tuna. Mol Ecol 2024; 33:e17188. [PMID: 37921120 DOI: 10.1111/mec.17188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 10/02/2023] [Accepted: 10/19/2023] [Indexed: 11/04/2023]
Abstract
The commercially important Atlantic bluefin tuna (Thunnus thynnus), a large migratory fish, has experienced notable recovery aided by accurate resource assessment and effective fisheries management efforts. Traditionally, this species has been perceived as consisting of eastern and western populations, spawning respectively in the Mediterranean Sea and the Gulf of Mexico, with mixing occurring throughout the Atlantic. However, recent studies have challenged this assumption by revealing weak genetic differentiation and identifying a previously unknown spawning ground in the Slope Sea used by Atlantic bluefin tuna of uncertain origin. To further understand the current and past population structure and connectivity of Atlantic bluefin tuna, we have assembled a unique dataset including thousands of genome-wide single-nucleotide polymorphisms (SNPs) from 500 larvae, young of the year and spawning adult samples covering the three spawning grounds and including individuals of other Thunnus species. Our analyses support two weakly differentiated but demographically connected ancestral populations that interbreed in the Slope Sea. Moreover, we also identified signatures of introgression from albacore (Thunnus alalunga) into the Atlantic bluefin tuna genome, exhibiting varied frequencies across spawning areas, indicating strong gene flow from the Mediterranean Sea towards the Slope Sea. We hypothesize that the observed genetic differentiation may be attributed to increased gene flow caused by a recent intensification of westward migration by the eastern population, which could have implications for the genetic diversity and conservation of western populations. Future conservation efforts should consider these findings to address potential genetic homogenization in the species.
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Affiliation(s)
- Natalia Díaz-Arce
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | | | - David E Richardson
- Northeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), Narragansett, Rhode Island, USA
| | - John F Walter
- Southeast Fisheries Sciences Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), Miami, Florida, USA
| | | | | | - Deirdre Brophy
- Marine and Freshwater Research Center, Atlantic Technological University (ATU), Galway City, Ireland
| | - Molly Lutcavage
- Large Pelagics Research Center, School for the Environment, University of Massachusetts Boston, Gloucester, Massachusetts, USA
| | - Piero Addis
- Department of Environmental and Life Science, University of Cagliari, Cagliari, Italy
| | - Francisco Alemany
- International Commission for the Conservation of Atlantic Tunas, GBYP, Madrid, Spain
| | - Robert Allman
- National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, Florida, USA
| | | | - Igaratza Fraile
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Pasaia, Spain
| | - Nicolas Goñi
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Pasaia, Spain
| | - Alex R Hanke
- St Andrews Biological Station, Fisheries and Oceans Canada, St. Andrews, New Brunswick, Canada
| | | | - Ashley Pacicco
- Cooperative Institute for Marine and Atmospheric Studies Rosenstiel School of Marine, Atmospheric and Earth Science, University of Miami, Miami, Florida, USA
| | - Joseph M Quattro
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, USA
| | - Jay R Rooker
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, USA
| | - Haritz Arrizabalaga
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Pasaia, Spain
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