[H-TT16] Development and application of environmental traceability methods

[HTT16-09] Reconstructing lifetime isotope baselines of fish from eye lenses

*Yota Harada¹, Shin-ichi Ito², Chisato Yoshikawa¹, Nanako O. Ogawa¹, Naoto Ishikawa¹, Naohiko Ohkouchi¹ (1.Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology, 2.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:isotope, nitrogen, fish

Compound-specific nitrogen isotope analysis of amino acids archived in eye lens laminae was carried out to reconstruct lifetime nitrogen isotope baselines and trophic position of Chub mackerel (Scomber japonicus), a commercially important fish species in Japan. The bulk ¹⁵N values gradually increased from the eye lens core (~ 2‰) to the outer layers (~ 10‰). The trophic position increased slightly from 2.6 (larval-juvenile stage) to 2.8 (adult stage). However, nitrogen baselines (phenylalanine) shifted substantially from -2.8‰ (larval-juvenile stage) to 2.8 (adult stage), likely associated with the typical ontogenetic migration of Chub mackerel in the western North Pacific that migrate from the subtropical ¹⁵N depleted Kuroshio region to subarctic ¹⁵N enriched Oyashio region. This study shows that lifetime trends in N isotope baselines can be reconstructed from eye lens laminae and are useful for studying ontogenetic migration of individual fish.