Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean

Type Article
Date 2019-01
Language English
Author(s) Sardenne Fany1, 2, Diaha N'Guessan Constance3, Amande Monin Justin3, Zudaire Iker1, 4, Couturier Lydie2, Metral LuisaORCID5, Le Grand Fabienne2, Bodin Nathalie1, 6
Affiliation(s) 1 : UM, Res Inst Sustainable Dev, Ctr Rech Halieut, UMR MARBEC,IRD,CNRS,Ifremer, Sete, France.
2 : Univ Western Brittany, UMR LEMAR, CNRS, UBO,IRD,Ifremer, Brest, France.
3 : Ctr Rech Oceanol, Abidjan, Cote Ivoire.
4 : Basque Fdn Sci, Ikerbasque, Bilbao, Spain.
5 : UM, UMR MARBEC, IFREMER, IRD,CNRS,Ctr Rech Halieut, Sete, France.
6 : Seychelles Fishing Author, Victoria, Seychelles.
Source Canadian Journal Of Fisheries And Aquatic Sciences (0706-652X) (Canadian Science Publishing, Nrc Research Press), 2019-01 , Vol. 76 , N. 1 , P. 69-80
DOI 10.1139/cjfas-2017-0368
Abstract

In the Gulf of Guinea, bigeye Thunnus obesus (BET) and yellowfin tuna Thunnus albacares (YFT) are important for commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes we examined their niche partitioning in this understudied region. Niche overlap was high (>70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high δ15N values and high proportions of mono-unsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (δ15N values decrease ~0.5 ‰) suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatoms marker (20:5n-3) increased in the seasonal upwelling area, highlighting the seasonal habitat influence on tunas diet. The relatively lipid-rich muscle (~6 % dry weight) of Atlantic tropical tunas suggested a richer diet in this region than for Indian Ocean tropical tunas and/or differences in energy allocation strategies.

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Sardenne Fany, Diaha N'Guessan Constance, Amande Monin Justin, Zudaire Iker, Couturier Lydie, Metral Luisa, Le Grand Fabienne, Bodin Nathalie (2019). Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean. Canadian Journal Of Fisheries And Aquatic Sciences, 76(1), 69-80. Publisher's official version : https://doi.org/10.1139/cjfas-2017-0368 , Open Access version : https://archimer.ifremer.fr/doc/00436/54796/