Bull. Jpn. Soc. Fish. Oceanogr. 73(1), Page 8-15, 2009   Ontogenetic changes of trace elements in otoliths and their spatial variations in rabbitfish, Siganus fuscescens Hideaki Yamada1† and Koij Baba2 1 Ishigaki Tropical Station, Seikai National Fisheries Research Institute, Fisheries Research Agency, 148-446, Fukai, Ishigaki, Okinawa 907-0451, Japan 2 National Institute for Agro-Environmental Sciences, 3-1-3 Tsukuba, Ibaraki 305-8604, Japan † e-mail: taihei@fra.affrc.go.jp In order to search for appropriate tracers of migration, ontogenetic changes of trace elements in the otoliths of the rabbitfish, Siganus fuscescens collected from four sites around Ishigaki island were examined by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Concentrations of Sr and Mg in the seawater samples were high in exposed areas, while those of Ba and Mn were high in embayment areas located in the vicinity of river mouths. However, ontogenetic changes of otolith Sr, Ba and Mg concentrations were not different among sampling sites. The otolith Sr and Ba concentrations reached the maximum values after settlement. The otolith Mg concentration decreased along the life history transect with a rapid decline during the pelagic larval stage. In contrast, the otolith Mn concentration was always higher in embayment areas than in exposed areas. These results suggest that the otolith Mn concentration can be used as an indicator of the migration pattern related to water chemistry. Key words: rabbitfish, LA-ICP-MS, otolith chemistry