Complex migration routes of Atlantic bluefin tuna (Thunnus thynnus) question current population structure paradigm

2010 ◽  
Vol 67 (6) ◽  
pp. 966-976 ◽  
Author(s):  
Benjamin Galuardi ◽  
François Royer ◽  
Walt Golet ◽  
John Logan ◽  
John Neilson ◽  
...  
Keyword(s):  
Site Fidelity ◽  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Migration Routes ◽  
Western Atlantic ◽  
Spawning Period ◽  
Atlantic Bluefin Tuna ◽  
Spawning Site ◽  
Archival Tags ◽  
Spawning Areas

Movements of Atlantic bluefin tuna ( Thunnus thynnus , ABFT) from specific western Atlantic forage grounds are not well described, and the extent of their spawning areas is mainly surmised. In 2005 and 2006, we deployed 41 pop-up satellite archival tags (PSATs) on adult Atlantic bluefin tuna off the coast of Nova Scotia, Canada, and on Georges Bank. During the assumed spawning period, 56% of the tagged ABFT occupied a known spawning area, while 44% were located in distant oceanic regions. Assuming obligate annual spawning, these results are inconsistent with the notion of spawning site fidelity to the Gulf of Mexico. The ocean-wide migrations of adult ABFT tagged on a common forage ground suggest evidence of a metapopulation requiring more spatially explicit management than the current simple two-stock structure.

scholarly journals Combining genetic markers with stable isotopes in otoliths reveals complexity in the stock structure of Atlantic bluefin tuna (Thunnus thynnus)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Deirdre Brophy ◽  
Naiara Rodríguez-Ezpeleta ◽  
Igaratza Fraile ◽  
Haritz Arrizabalaga
Keyword(s):  
Genetic Markers ◽  
Bluefin Tuna ◽  
Integrated Model ◽  
Stock Structure ◽  
Thunnus Thynnus ◽  
Integrated Method ◽  
Atlantic Bluefin Tuna ◽  
Spawning Areas ◽  
Otolith Core ◽  
First Year Of Life

Abstract Atlantic bluefin tuna (Thunnus thynnus) from the two main spawning populations in the Mediterranean and Gulf of Mexico occur together in the western, central and eastern Atlantic. Stock composition of catches from mixing areas is uncertain, presenting a major challenge to the sustainable management of the fisheries. This study combines genetic and chemical markers to develop an integrated method of population assignment. Stable isotope signatures (δ13C and δ18O) in the otolith core of adults from the two main spawning populations (adult baselines) showed less overlap than those of yearlings (12–18 months old) from western and eastern nursery areas suggesting that some exchange occurs towards the end of the yearling phase. The integrated model combined δ18O with four genetic markers (SNPs) to distinguish the adult baselines with greater accuracy than chemical or genetic markers alone. When used to assign individuals from the mixing areas to their population of origin, the integrated model resolved some (but not all) discrepancies between the chemistry and genetic methods. Some individuals in the mixing area had otolith δ18O values and genetic profiles which when taken together, were not representative of either population. These fish may originate from another Atlantic spawning area or may represent population contingents that move away from the main spawning areas during the first year of life. This complexity in stock structure is not captured by the current two-stock model.

Diet of young Atlantic bluefin tuna (Thunnus thynnus) in eastern and western Atlantic foraging grounds

2010 ◽  
Vol 158 (1) ◽  
pp. 73-85 ◽  
Author(s):  
John M. Logan ◽  
Enrique Rodríguez-Marín ◽  
Nicolas Goñi ◽  
Santiago Barreiro ◽  
Haritz Arrizabalaga ◽  
...  
Keyword(s):  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Western Atlantic ◽  
Atlantic Bluefin Tuna

scholarly journals Erratum to: Diet of young Atlantic bluefin tuna (Thunnus thynnus) in eastern and western Atlantic foraging grounds

2011 ◽  
Vol 158 (9) ◽  
pp. 2147-2148 ◽  
Author(s):  
John M. Logan ◽  
Enrique Rodríguez-Marín ◽  
Nicolas Goñi ◽  
Santiago Barreiro ◽  
Haritz Arrizabalaga ◽  
...  
Keyword(s):  
Bluefin Tuna ◽  
Thunnus Thynnus ◽  
Western Atlantic ◽  
Atlantic Bluefin Tuna

scholarly journals Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags

PLoS ONE ◽  
2009 ◽  
Vol 4 (7) ◽  
pp. e6151 ◽  
Author(s):  
Andreas Walli ◽  
Steven L. H. Teo ◽  
Andre Boustany ◽  
Charles J. Farwell ◽  
Tom Williams ◽  
...  
Keyword(s):  
Bluefin Tuna ◽  
Diving Behavior ◽  
Thunnus Thynnus ◽  
Seasonal Movements ◽  
Atlantic Bluefin Tuna ◽  
Archival Tags

Natal origin of Atlantic bluefin tuna (Thunnus thynnus) from Canadian waters based on otolith δ13C and δ18O

2010 ◽  
Vol 67 (3) ◽  
pp. 563-569 ◽  
Author(s):  
Ryan W. Schloesser ◽  
John D. Neilson ◽  
David H. Secor ◽  
Jay R. Rooker
Keyword(s):  
Eastern Mediterranean ◽  
Bluefin Tuna ◽  
Maximum Likelihood Estimates ◽  
Thunnus Thynnus ◽  
Western Atlantic ◽  
Atlantic Bluefin Tuna ◽  
Declining Populations ◽  
Catch Rates ◽  
And Migration ◽  
Stock Mixing

Increased knowledge of stock mixing and migration of Atlantic bluefin tuna ( Thunnus thynnus ) is required to properly manage and conserve declining populations. Here, we predicted the nursery origin of giant bluefin tuna (n = 224) present in samples from Canadian waters using stable δ13C and δ18O isotopes in otoliths. The isotopic composition of milled otolith cores (corresponding to the first year of life) of giant bluefin tuna from three decades (1970s, 1980s, 2000s) and three regions within or adjacent to the Gulf of St. Lawrence was compared with otolith δ13C and δ18O of yearling bluefin tuna collected from eastern (Mediterranean Sea – eastern Atlantic, n = 136) and western (western Atlantic, n = 103) nurseries. Maximum likelihood estimates indicated that greater than 99% of bluefin tuna in our Canadian samples originated from the western nursery. No significant differences in estimates of origin for bluefin tuna were detected among decades or among regions, suggesting little to no mixing of eastern and western populations in the Canadian samples examined. These findings justify the use of catch rates from the Gulf of St. Lawrence area as an index of abundance for the oldest members of the western population.

scholarly journals Discovery of a spawning ground reveals diverse migration strategies in Atlantic bluefin tuna (Thunnus thynnus)

2016 ◽  
Vol 113 (12) ◽  
pp. 3299-3304 ◽  
Author(s):  
David E. Richardson ◽  
Katrin E. Marancik ◽  
Jeffrey R. Guyon ◽  
Molly E. Lutcavage ◽  
Benjamin Galuardi ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Mediterranean Sea ◽  
Bluefin Tuna ◽  
Spawning Ground ◽  
International Consensus ◽  
Western Atlantic ◽  
Atlantic Bluefin Tuna ◽  
Anthropogenic Stressors ◽  
Spawning Site ◽  
Migration Strategies

Atlantic bluefin tuna are a symbol of both the conflict between preservationist and utilitarian views of top ocean predators, and the struggle to reach international consensus on the management of migratory species. Currently, Atlantic bluefin tuna are managed as an early-maturing eastern stock, which spawns in the Mediterranean Sea, and a late-maturing western stock, which spawns in the Gulf of Mexico. However, electronic tagging studies show that many bluefin tuna, assumed to be of a mature size, do not visit either spawning ground during the spawning season. Whether these fish are spawning in an alternate location, skip-spawning, or not spawning until an older age affects how vulnerable this species is to anthropogenic stressors including exploitation. We use larval collections to demonstrate a bluefin tuna spawning ground in the Slope Sea, between the Gulf Stream and northeast United States continental shelf. We contend that western Atlantic bluefin tuna have a differential spawning migration, with larger individuals spawning in the Gulf of Mexico, and smaller individuals spawning in the Slope Sea. The current life history model, which assumes only Gulf of Mexico spawning, overestimates age at maturity for the western stock. Furthermore, individual tuna occupy both the Slope Sea and Mediterranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete spawning-site fidelity. Overall, this complexity of spawning migrations questions whether there is complete independence in the dynamics of eastern and western Atlantic bluefin tuna and leads to lower estimates of the vulnerability of this species to exploitation and other anthropogenic stressors.

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