Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean

Patrick Houssard; Anne Lorrain; Laura Tremblay-Boyer; Valérie Allain; Brittany S. Graham; Christophe E. Menkès; Heidi R. Pethybridge; Lydie I.E. Couturier; David Point; Bruno Leroy; Aurore Receveur; Brian P.V. Hunt; Elodie Vourey; Sophie Bonnet; Martine Rodier; Patrick Raimbault; Eric Feunteun; Petra M. Kuhnert; Jean-Marie Munaron; Benoit Lebreton; Tsuguo Otake; Yves Letourneur

doi:10.1016/j.pocean.2017.04.008

Journal articles

Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean

Patrick Houssard ^{1, 2, 3} Anne Lorrain ^{1, 3} Laura Tremblay-Boyer ⁴ Valérie Allain ⁴ Brittany S. Graham ⁵ Christophe E. Menkès ⁶ Heidi R. Pethybridge ⁷ Lydie I.E. Couturier ¹ David Point ⁸ Bruno Leroy ⁴ Aurore Receveur ⁴ Brian P.V. Hunt ⁹ Elodie Vourey ⁴ Sophie Bonnet ¹⁰ Martine Rodier ^{11, 12} Patrick Raimbault ¹⁰ Eric Feunteun ^{13, 14} Petra M. Kuhnert ¹⁵ Jean-Marie Munaron ¹ Benoit Lebreton ¹⁶ Tsuguo Otake Yves Letourneur ²

1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)

2 LIVE - Laboratoire Insulaire du Vivant et de l'Environnement

3 IRD - Institut de Recherche pour le Développement

4 SPC - Pacific community

5 NIWA - National Institute of Water and Atmospheric Research [Wellington]

6 PEPS - Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs

LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

7 CSIRO Marine and Atmosphere Research [Hobart]

8 GET - Géosciences Environnement Toulouse

9 UBC - University of British Columbia

10 MIO - Institut méditerranéen d'océanologie

11 IRD [Polynésie] - Institut de Recherche pour le Développement

12 EIO - Ecosystèmes Insulaires Océaniens (UMR 241)

13 BOREA - Biologie des Organismes et Ecosystèmes Aquatiques

14 Station marine Dinard

15 CSIRO - Data61 [Canberra]

16 LIENSs - LIttoral ENvironnement et Sociétés - UMRi 7266

Abstract : Estimates of trophic position are used to validate ecosystem models and understand food web structure. A consumer's trophic position can be estimated by the stable nitrogen isotope values (delta N-15) of its tissue, once the baseline isotopic variability has been accounted for. Our study established the first data-driven baseline delta N-15 isoscape for the Western and Central Pacific Ocean using particulate organic matter. Bulk delta N-15 analysis on 1039 muscle tissue of bigeye and yellowfin tuna were conducted together with amino acid compound-specific delta N-15 analysis (AA-CSIA) on a subset of 21 samples. Both particulate organic matter and tuna bulk delta N-15 values varied by more than 10 parts per thousand across the study area. Fine-scaled trophic position maps were constructed and revealed higher tuna trophic position (by similar to 1) in the southern latitudes compared to the equator. AA-CSIA confirmed these spatial patterns for bigeye and, to a lesser extent, yellowfin tuna. Using generalized additive models, spatial variations of tuna trophic positions were mainly related to the depth of the 20 degrees C isotherm, a proxy for the thermocline behavior, with higher tuna trophic position estimates at greater thermocline depths. We hypothesized that a deeper thermocline would increase tuna vertical habitat and access to mesopelagic prey of higher trophic position. Archival tagging data further suggested that the vertical habitat of bigeye tuna was deeper in the southern latitudes than at the equator. These results suggest the importance of thermocline depth in influencing tropical tuna diet, which affects their vulnerability to fisheries, and may be altered by climate change.

Keywords : Amino acid Depth of the 20°C isotherm Nitrogen isotopes POM Yellowfin tuna Isoscapes Bigeye tuna ACL Biochemical markers Compound-specific isotope analysis

Document type :

Journal articles

Domain :

Life Sciences [q-bio] / Ecology, environment

Environmental Sciences / Biodiversity and Ecology

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https://hal-amu.archives-ouvertes.fr/hal-01621952
Contributor : Valerie Michotey <>
Submitted on : Monday, October 23, 2017 - 9:25:22 PM
Last modification on : Monday, June 29, 2020 - 11:50:03 PM

Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean

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Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean

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