Scientific Reports (Jul 2021)

Natal origin and age-specific egress of Pacific bluefin tuna from coastal nurseries revealed with geochemical markers

  • Jay R. Rooker,
  • R. J. David Wells,
  • Barbara A. Block,
  • Hui Liu,
  • Hannes Baumann,
  • Wei-Chuan Chiang,
  • Michelle Zapp Sluis,
  • Nathaniel R. Miller,
  • John A. Mohan,
  • Seiji Ohshimo,
  • Yosuke Tanaka,
  • Michael A. Dance,
  • Heidi Dewar,
  • Owyn E. Snodgrass,
  • Jen-Chieh Shiao

DOI
https://doi.org/10.1038/s41598-021-93298-2
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 13

Abstract

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Abstract Geochemical chronologies were constructed from otoliths of adult Pacific bluefin tuna (PBT) to investigate the timing of age-specific egress of juveniles from coastal nurseries in the East China Sea or Sea of Japan to offshore waters of the Pacific Ocean. Element:Ca chronologies were developed for otolith Li, Mg, Mn, Zn, Sr, and Ba, and our assessment focused on the section of the otolith corresponding to the age-0 to age-1 + interval. Next, we applied a common time-series approach to geochemical profiles to identify divergences presumably linked to inshore-offshore migrations. Conspicuous geochemical shifts were detected during the juvenile interval for Mg:Ca, Mn:Ca, and Sr:Ca that were indicative of coastal-offshore transitions or egress generally occurring for individuals approximately 4–6 mo. old, with later departures (6 mo. or older) linked to overwintering being more limited. Changepoints in otolith Ba:Ca profiles were most common in the early age-1 period (ca. 12–16 mo.) and appear associated with entry into upwelling areas such as the California Current Large Marine Ecosystem following trans-Pacific migrations. Natal origin of PBT was also predicted using the early life portion of geochemical profile in relation to a baseline sample comprised of age-0 PBT from the two primary spawning areas in the East China Sea and Sea of Japan. Mixed-stock analysis indicated that the majority (66%) of adult PBT in our sample originated from the East China Sea, but individuals of Sea of Japan origin were also detected in the Ryukyu Archipelago.