Dataset: Bulk Raw Isotopes - Tunas
Deployment: IATTC_03-05

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.

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’s 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 < +/- 0.1 ‰ (1 sd) based on triplicate analysis of in-house reference materials (glycine standard and tuna muscle) with known δ15N values.