Oceanographic changes and exploitation drive the spatio-temporal dynamics of Atlantic bluefin tuna (Thunnus thynnus)

Type Article
Date 2014-03
Language English
Author(s) Fromentin Jean-Marc1, Reygondeau Gabriel2, Bonhommeau SylvainORCID1, Beaugrand Gregory3
Affiliation(s) 1 : Ifremer Inst Francais Rech Exploitat Mer, UMR EME 212, F-34203 Sete, France.
2 : IRD, UMR EME 212, F-34203 Sete, France.
3 : CNRS, UMR LOG 8187, F-62930 Wimereux, France.
Source Fisheries Oceanography (1054-6006) (Wiley-blackwell), 2014-03 , Vol. 23 , N. 2 , P. 147-156
DOI 10.1111/fog.12050
WOS© Times Cited 20
Keyword(s) ecological niche model, longline fisheries, migration, synergistic effects, Thunnus thynnus, time series
Abstract Atlantic bluefin tuna (ABFT) has always displayed spectacular changes in its spatial distribution, but the underlying mechanism of such variations still remains obscure. This study focuses on this challenging issue by scrutinizing the intriguing ‘Brazilian episode’ during which a large quantity of ABFT (a temperate species) was caught during the 1960s in the equatorial Atlantic. To investigate this event, we applied a niche model to an extensive data set of catch and environmental variables from 1960 to 2009. ABFT exhibited a remarkably large ecological niche, which matches well with our current knowledge of ABFT. Our results also depicted a high probability of ABFT occurrence in the South Atlantic and, more interestingly, favorable environmental conditions in the western equatorial Atlantic during the 1960s, but not later. ABFT could thus have migrated from their northern spawning grounds to the South Atlantic during the 1960s through the western equatorial Atlantic, playing the role of an ‘ecological bridge’. We argue that the rarity of ABFT in the southern Atlantic during the last four decades would result from the interaction of several processes, particularly oceanographic conditions, migratory behavior, density-dependence, exploitation levels and population structure. Examination of the catch data further indicated that the fish caught in the equatorial Atlantic were from the western stock and we concluded that the lack of rebuilding of this stock could result from a regime shift due to the combination of oceanographic changes in the equatorial Atlantic and overfishing in the North Atlantic in the 1960s and 1970s.
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Fromentin Jean-Marc, Reygondeau Gabriel, Bonhommeau Sylvain, Beaugrand Gregory (2014). Oceanographic changes and exploitation drive the spatio-temporal dynamics of Atlantic bluefin tuna (Thunnus thynnus). Fisheries Oceanography, 23(2), 147-156. Publisher's official version : https://doi.org/10.1111/fog.12050 , Open Access version : https://archimer.ifremer.fr/doc/00164/27540/