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MEPS
Marine Ecology Progress Series

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MEPS 645:171-185 (2020)  -  DOI: https://doi.org/10.3354/meps13363

Assessing residency and movement dynamics of swordfish Xiphias gladius in the Eastern North Pacific Ocean using stable isotope analysis

Tatiana A. Acosta-Pachón1,3,*, Sofía Ortega-García1, Brittany Graham2

1Instituto Politécnico Nacional-CICIMAR, Departamento de Pesquerías y Biología Marina, La Paz, Baja California Sur 23096, Mexico
2National Institute of Water and Atmospheric (NIWA) Research Ltd., Wellington 6021, New Zealand
3Present address: Universidad Autónoma de Baja California Sur, Departamento Académico de Ciencias Marinas y Costeras, La Paz, Baja California Sur 23080, Mexico
*Corresponding author:

ABSTRACT: Swordfish are migratory fish that inhabit tropical to temperate waters, but little is known about movement patterns or mixing between subpopulations of this species. This study examines carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in growth rings of the anal fin spine and muscle tissue of swordfish from 3 different areas of the Eastern North Pacific Ocean (ENPO)—off Baja California Sur (Mexico) and California (USA), and in the North Pacific Subtropical Gyre (NPSG)—to assess swordfish movements between these areas. The analysis of δ13C and δ15N revealed no relationship between fish size and δ15N, suggesting a consistent consumption of prey items by this species over time. Differences between the anal fin spine and muscle were found, but interpreting these isotopic differences requires information on tissue-specific isotope turnover rates. The spatial pattern suggests that swordfish populations from these areas in the ENPO exhibit a relatively unexpected homing behavior at the temporal scale, according to anal spine and muscle turnover rates. Our findings support that swordfish may show site fidelity, which has important implications for their management and stock assessments.


KEY WORDS: Billfish · δ13C · δ15N · Muscle · Anal fin spine


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Cite this article as: Acosta-Pachón TA, Ortega-García S, Graham B (2020) Assessing residency and movement dynamics of swordfish Xiphias gladius in the Eastern North Pacific Ocean using stable isotope analysis. Mar Ecol Prog Ser 645:171-185. https://doi.org/10.3354/meps13363

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