Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean
|Author(s)||Sardenne Fany1, 2, Diaha N'Guessan Constance3, Amande Monin Justin3, Zudaire Iker1, 4, Couturier Lydie2, Metral Luisa5, 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|
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.