MEPS 553:253-266 (2016)  -  DOI:

Intrinsic tracers reveal recent foraging ecology of giant Pacific bluefin tuna at their primary spawning grounds

Daniel J. Madigan1,*, Wei-Chuan Chiang2, Natalie J. Wallsgrove3, Brian N. Popp3, Takashi Kitagawa4, C. Anela Choy5, Jocelyn Tallmon6, Nazmul Ahmed6, Nicholas S. Fisher6, Chi-lu Sun7,8

1Harvard University Center for the Environment, Harvard University, Cambridge, MA 02138, USA
2Eastern Marine Biology Research Center, Fisheries Research Institute, Taitung, 96143, Taiwan
3Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822, USA
4Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan
5Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
6School of Marine and Atmospheric Science & Institute for Ocean Conservation Science, Stony Brook University, Stony Brook, NY 11794, USA
7National Taiwan Ocean University, No. 2, Keelung City 202, Taiwan
8National Taiwan University, No. 1, Taipei 10617, Taiwan
*Corresponding author:

ABSTRACT: Pacific bluefin tuna Thunnus orientalis (PBFT) play important economic and ecological roles in the western Pacific Ocean. We currently lack basic information on PBFT foraging that would facilitate ecologically informed recovery strategies for this species. We used stable isotope analysis to investigate recent (previous ~1.5 yr based on isotopic turnover rate) trophic ecology of 261 giant (>180 cm), sexually mature PBFT entering their major spawning grounds off Taiwan. We performed amino acid-compound specific isotope analysis (AA-CSIA) on a subset of PBFT and select prey to assess the trophic position of PBFT in the western Pacific and to validate putative recent trans-Pacific migration from the eastern Pacific Ocean. Bayesian isotopic mixing model results suggested recent PBFT foraging off eastern Japan and in the Kuroshio-Oyashio transition region, with minimal inputs from the Sea of Japan and Taiwan waters. PBFT did not appear to feed primarily on zooplanktivorous forage fish (e.g. sardine, anchovy) but on higher trophic-level prey including mackerels, squids, and pomfrets. AA-CSIA confirmed a high trophic position (>5) of PBFT in this region and identified putative recent trans-Pacific migration of 2 individuals. This study identifies the prey base that sustains giant PBFT before migrating to spawning grounds off Taiwan and sets the stage for future studies comparing the movements and ecology of PBFT in the western Pacific Ocean.

KEY WORDS: Thunnus orientalis · Stable isotopes · AA-CSIA · Diet · Trophic

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Cite this article as: Madigan DJ, Chiang WC, Wallsgrove NJ, Popp BN and others (2016) Intrinsic tracers reveal recent foraging ecology of giant Pacific bluefin tuna at their primary spawning grounds. Mar Ecol Prog Ser 553:253-266.

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