Adult female loggerhead turtles around Japan 1999

Original provider:
Atmosphere and Ocean Research Institute, University of Tokyo

Dataset credits:
Hideo Hatase, Atmosphere and Ocean Research Institute, University of Tokyo

Abstract:
Stable isotope analyses and satellite telemetry were used to investigate the relationship between the body size and feeding habitat of adult female loggerhead turtles Caretta caretta around Japan. A total of 149 females from 2 nesting sites, 600 km apart, 1 in Minabe and 1 in Yakushima, was examined by stable isotope analyses of the egg-yolk in 1998 and 1999. Since there were neither significant intra- nor inter-clutch variations in δ13C or δ15N egg-yolks from the same female, the isotope signatures of a single egg-yolk from any clutch in a nesting season could be used to represent those of its nesting female. Both isotopic values increased as the body size of the nesting female increased, irrespective of nesting site. Comparisons between isotopic values of loggerhead egg-yolks and prey items revealed size-related differences among both feeding habits (planktonic or benthic) and habitat areas (pelagic or neritic) of female loggerheads. In 1999, 5 females nesting in Minabe were tracked by satellite. After the nesting season, 2 females with low isotopic values migrated to the pelagic Pacific along the Kuroshio Current, whereas 3 with high isotopic values migrated to the neritic East China Sea. The former females were smaller than the latter. These results were consistent with inferences from stable isotope analyses and previous findings, indicating that the body size, habitat area, and feeding habit of female loggerheads around Japan are closely related. In addition, there were no significant differences in δ13C or δ15N between recruits and remigrants, implying that female loggerheads do not change their feeding habitats during the reproductive stage. We postulate that female habitat selection as a function of body size is closely related to the recruitment and settlement in immature loggerheads, which return to Japan after developmental migrations in the North Pacific.

原始提供方：
东京大学大气海洋研究所（Atmosphere and Ocean Research Institute, University of Tokyo）

数据集贡献者：
东京大学大气海洋研究所的Hideo Hatase

摘要：
本研究借助稳定同位素分析（stable isotope analyses）与卫星遥测（satellite telemetry）技术，旨在探究日本周边成年雌性蠵龟（Caretta caretta）的体型与摄食栖息地之间的关联。1998年与1999年，研究人员对两处相距600公里的产卵场的149只雌性蠵龟开展卵黄稳定同位素分析，两处产卵场分别位于南部（Minabe）与屋久岛（Yakushima）。由于同一只雌性个体的卵黄δ¹³C与δ¹⁵N均不存在显著的窝内与窝间差异，因此可利用繁殖季内任意一窝卵的单份卵黄同位素信号，表征该产卵雌性的同位素特征。无论产卵场位置如何，两种同位素比值均随产卵雌性的体型增大而升高。通过对比蠵龟卵黄与猎物的同位素值，可发现雌性蠵龟的摄食习性（浮游性或底栖性）与栖息地类型（远洋或近岸浅海）均存在与体型相关的差异。1999年，研究人员对在南部产卵的5只雌性蠵龟进行卫星追踪：繁殖季结束后，2只同位素值较低的个体沿黑潮（Kuroshio Current）向太平洋远洋区洄游，而3只同位素值较高的个体则洄游至东中国海近岸海域；前者体型小于后者。该结果与稳定同位素分析的推论及既往研究结果一致，表明日本周边雌性蠵龟的体型、栖息地类型与摄食习性三者密切相关。此外，初次繁殖个体与重复繁殖个体的δ¹³C与δ¹⁵N均无显著差异，这意味着雌性蠵龟在繁殖阶段不会改变其摄食栖息地。我们推测，雌性个体依据体型进行的栖息地选择，与在北太平洋完成发育洄游后返回日本的幼年蠵龟的招募与定居过程紧密相关。