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

Trophic position increases with thermocline depth in yellowfin and bigeye tuna across the Western and Central Pacific Ocean Houssard P. auteur aut IRD Lorrain Anne auteur aut IRD Tremblay-Boyer L. auteur aut IRD Allain V. auteur aut IRD Graham B. S. auteur aut IRD Menkès Christophe auteur aut IRD Pethybridge H. auteur aut IRD Couturier L. I. E. auteur aut IRD Point David auteur aut IRD Leroy B. auteur aut IRD Receveur A. auteur aut IRD Hunt B. P. V. auteur aut IRD Vourey E. auteur aut IRD Bonnet Sophie auteur aut IRD Rodier Martine auteur aut IRD Raimbault P. auteur aut IRD Feunteun E. auteur aut IRD Kuhnert P. M. auteur aut IRD Munaron Jean-Marie auteur aut IRD Lebreton B. auteur aut IRD Otake T. auteur aut IRD Letourneur Y. auteur aut IRD text journalArticle eng text/pdf born digital access 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. specialized Nitrogen isotopes POM Isoscapes Bigeye tuna Yellowfin tuna Depth of the 20 degrees C isotherm Amino acid Compound-specific isotope analysis Biochemical markers PACIFIQUE OUEST PACIFIQUE CENTRE ZONE TROPICALE ZONE EQUATORIALE 036 020 021 Progress in Oceanography 154 49-63 2017 0079-6611 https://www.documentation.ird.fr/hor/fdi:010070302 10.1016/j.pocean.2017.04.008 0079-6611 [F B010070302] https://www.documentation.ird.fr/hor/fdi:010070302 https://www.documentation.ird.fr/intranet/publi/2017/08/010070302.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2017-09-05 2023-07-11 fdi:010070302 fre