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MEPS 673:165-181 (2021)  -  DOI:

Discrimination of yellowfin tuna Thunnus albacares between nursery areas in the Indian Ocean using otolith chemistry

Iraide Artetxe-Arrate1,*, Igaratza Fraile1, Naomi Clear2, Audrey M. Darnaude3, David L. Dettman4, Christophe Pécheyran5, Jessica Farley2, Hilario Murua6

1AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Pasaia, Gipuzkoa 20110, Spain
2CSIRO Oceans and Atmosphere, Hobart, Tasmania 7000, Australia
3Marbec, Univ Montpellier, CNRS, Ifremer, IRD, 34095 Montpellier, France
4Environmental Isotope Laboratory, Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA
5IPREM, Institut des sciences analytiques et de physico-chimie pour l’environnement et les matériaux, Université de Pau et des Pays de l’Adour, 64000 Pau, France
6International Seafood Sustainability Foundation, Washington, DC 20005, USA
*Corresponding author: ,

ABSTRACT: Yellowfin tuna Thunnus albacares is a highly exploited species in the Indian Ocean. Yet, its stock structure is still not well understood, hindering assessment of the stock at a suitable spatial scale for management. Here, young-of-the-year (<4 mo) yellowfin tuna otoliths were collected in 2018 and 2019, from 4 major nursery areas in the Indian Ocean: Madagascar, Seychelles-Somalia, Maldives and Sumatra. First, direct age estimates were made in a subset of otoliths by visually counting microincrements to identify the portion of the otolith corresponding to the larval stage. We then developed 2-dimensional maps of trace element concentrations to examine spatial distribution of elements across otolith transverse sections. Different distribution patterns were observed among the elements analysed; Li, Sr and Ba were enriched in the portion of the otolith representing early life, whereas Mn and Mg concentrations were heterogeneous across growth bands. Last, we analysed inter-annual and regional variation in otolith chemical composition using both trace elements (Li, Mg, Sr, Ba and Mn) and stable isotopes (δ13C and δ18O). Significant regional variation in otolith chemical signatures was detected among nurseries, except between Madagascar and Seychelles-Somalia. Otolith δ13C and δ18O were important drivers of differentiation between western (Madagascar and Seychelles-Somalia), Maldives and Sumatra nurseries, whereas the elemental signatures were cohort specific. Overall nursery assignment accuracies were 69-71%. The present study demonstrates that baseline chemical signatures in the otoliths of yellowfin tuna are regionally distinct and can be used as a natural tag to investigate the nursery origin of older individuals in the Indian Ocean.

KEY WORDS: Otolith microchemistry · Yellowfin tuna · Otolith elemental fingerprints · Nursery discrimination · Trace elements · Stable carbon and oxygen isotopes · Stock structure

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Cite this article as: Artetxe-Arrate I, Fraile I, Clear N, Darnaude AM and others (2021) Discrimination of yellowfin tuna Thunnus albacares between nursery areas in the Indian Ocean using otolith chemistry. Mar Ecol Prog Ser 673:165-181.

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