Natal origin of Pacific bluefin tuna Thunnus orientalis inferred from otolith oxygen isotope composition
Resource
Marine Ecology Progress Series, 420, 207-219
Journal
Marine Ecology Progress Series
Journal Volume
420
Pages
207-219
Date Issued
2010
Author(s)
Wang, Shi-Wei
Yokawa, Kotaro
Ichinokawa, Momoko
Takeuchi, Yukio
Abstract
Pacific bluefin tuna Thunnus orientalis has 2 spawning grounds with different spawning seasons. One is in the northwest region of the Philippine Sea during May to June and the other is in the Japan Sea from late July to August. The oxygen isotope level in otoliths is affected by water oxygen isotope composition and negatively correlated to the ambient water temperature. We developed a technique using the temporal profiles of otolith 18 O to discriminate the natal origin of Pacific bluefin tuna. For Age-0 tuna caught in the Japan Sea (n = 35), the 18 O values varied from -2.5 to -2.2 between the otolith core and a distance of ca. 600 m from the core, and then the values increased (enriched) to about -0.8 to -1 at 700 to 1000 m. For Age-0 tuna caught in the Pacific Ocean (n = 41), the otolith 18 O values varied between -2.8 and -2.2 at 0 to 1000 m from the otolith core and then increased to ca. -1.5 to -1 at around 1200 to 1600 m from the core. The different profiles of otolith 18 O values between tuna caught in the Pacific Ocean and the Japan Sea evidently reflect different water temperatures along the migratory route from their natal origin. Fish hatched in the Japan Sea experience water temperatures of <15C in winter, about 4 mo after hatching, while fish hatched in the Philippine Sea experience winter water temperatures of 17 to 18C about 6 mo after hatching. The temporal difference in experienced water temperatures produces an earlier increase of otolith 18 O values for tuna caught in the Japan Sea than in the Pacific Ocean. The location of the first winter signal recorded as enriched 18 O in the otolith is a valuable proxy for tracking the natal origin of Pacific bluefin tuna.
SDGs
Type
journal article