Sampling Methodology: Three species of tuna, yellowfin (Ta.; Thunnus albacares), skipjack (Kp.; Katsuwonus pelamis), and bigeye (To.; Thunnus obesus) tunas, were sampled year-round during 2003-2005 by observers of the Inter-American Tropical Tuna Commission onboard purse-seine fishing vessels. Samples of dorsal white muscle were taken from each fish adjacent to the second dorsal fin. Fish of uniform size were used for analysis: skipjack tuna 450-550 mm, yellowfin tuna 500-700 mm, and bigeye tuna 450-550 mm. All samples were stored frozen until further processing in the laboratory.
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Analytical Methodology: Methods are described in Hetherington et al. (2016). Briefly: Isotopic analysis of bulk muscle tissue of the tunas was performed at the University of Hawaii\u2019s Isotope Biogeochemistry Laboratory. Stable isotope values of nitrogen were determined using an on-line carbon-nitrogen analyzer coupled with an isotope ratio mass spectrometer (FinniganConFlo II/Delta-Plus). Isotope values are reported in conventional delta-notation relative to the international standards, atmospheric N2 and V-PDB, for N and C, respectively. Mean accuracy of all stable isotopic analyses was < +/-\u00a00.1 \u2030 (1 sd) based on triplicate analysis of in-house reference materials (glycine standard and tuna muscle) with known \u03b415N values.
Data Processing:\u00a0Stable isotope analysis of carbon and nitrogen isotopes measures the ratio of the heavier, rare isotope to the lighter, more common isotope (13C:12C or \u03b413C;15N:14N or \u03b415N) expressed as parts per mil (\u2030) relative to a standard (air for N, V-PDB for C).
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BCO-DMO Processing:
\n- modified parameter names to conform with BCO-DMO naming conventions;
\n- re-formatted date to yyyy-mm-dd;
\n- replaced spaces with underscores in species name column.