Study of tuna life history by otolith stable carbon and oxygen isotope composition
Date Issued
2008
Date
2008
Author(s)
Wang, Shih-Wei
Abstract
Otolith, as a metabolically inert structure, can record the environmental history throughout fish life. This study aims to evaluate the life histories of tropic and temperate tunas by stable isotopic signature stored in otoliths. Stable 13C can reflect the diet of fishes, and stable 18O can record the environmental temperature. It can be another method to study tuna life history except for tagging or catch data analyzing.n this study, we first confirm the feasibility of stable isotope 13C and 18O stored in tuna otoliths, and then utilizing them to explain the Pacific bluefin tuna (PBF) life history, comparing the differences between tropic (PBF) and temperate (Yellowfin YFT and Bigeye BET) tunas. Profiles of 18O suggested a warm water period during the larval and juvenile stages, followed by water temperature decrease. Water temperature dramatically increased during the young stage then the values moderately fluctuated for the remaining life. This result suggested that hatched PBF stayed in tropical spawning ground, then transported by Kuroshio Current to temperate areas. PBF experienced cool water after detraining from the Kuroshio. The water temperature increased at the young stage may reflect the body temperature due to thermoregulation rather than the ambient water temperature. Supposing that PBF hatched in Japan sea, the high water temperate may represent the particular water mass rather than real water temperature. PBF experienced cool water after departing from Japan sea up to the open sea. BET and YFT show slow water temperature decrease and no apparent rising thereafter. This result indicates that BET and YFT reside in tropic areas, and reflect the different residing depth. Another aim is to set up the fingerprint of two Pacific bluefin spawning grounds (Kuroshio and Japan Sea) by 13C、18O and daily growth increments widths (DGI) in otoliths. The result show significant discrimination between two spawning grounds, and reveal the water mass mixing status.
Subjects
otolith
stable 13C and 18O isotope
tuna life history
DGI
spawning ground
Type
thesis
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