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

Type Article
Date 2019
Language English
Author(s) Sardenne Fany1, 2, Diaha N’guessan Constance3, Amandé Monin Justin3, Zudaire Iker4, 5, Couturier Lydie I. E.2, Metral LuisaORCID6, Le Grand Fabienne2, Bodin Nathalie1, 7
Affiliation(s) 1 : Research Institute for Sustainable Development (IRD), UMR MARBEC IRD/CNRS/Ifremer/UM, Centre de Recherche Halieutique, Sète, France
2 : University of Western Brittany (UBO), UMR LEMAR CNRS/UBO/IRD/Ifremer, Brest, France
3 : Centre de Recherches Océanologiques , Abidjan, Côte d'Ivoire
4 : Institut de recherche pour le developpement France-Sud, 98751, UMR MARBEC, Sète, France
5 : IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
6 : IFREMER, UMR MARBEC IRD/CNRS/Ifremer/UM, Centre de Recherche Halieutique, Sète, France
7 : Seychelles Fishing Authority, 280177, Victoria, Mahe, Seychelles
Source Canadian Journal of Fisheries and Aquatic Sciences (0706-652X) (Canadian Science Publishing), 2019 , Vol. 76 , N. 1 , P. 69-80
DOI 10.1139/cjfas-2017-0368
Keyword(s) niche overlap, fatty acids, stable isotopes, body condition, pelagic predators
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, Amandé Monin Justin, Zudaire Iker, Couturier Lydie I. E., 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/