1Laboratory of Ichthyology, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, 2Center for Water Environment Studies, Ibaraki University, Itako, Ibaraki 311-2402, Japan
The migratory history of yellowfin goby Acanthogobius flavimanus collected from brackish and fresh waters in Tokyo Bay and its adjacent rivers, central Japan was examined using otolith Sr:Ca ratios of 61 specimens (52.4-131.8 mm in standard length, SL). All the 21 yellowfin gobies collected from the fresh waters had higher Sr:Ca ratios (3.0-7.5×10−3) at the central otolith area, suggesting their origin was estuarine or marine areas, and the ratios decreased rapidly to 2.5×10−3 and lower toward the otolith edge, indicating their upstream migration to fresh waters in the juvenile stage. Of 40 specimens collected from brackish waters, 31 specimens were determined not to have experience of upstream migration and eight specimens to have temporarily entered or to have been momentarily exposed to fresh waters. The remaining one specimen of 96.5 mm SL had higher Sr:Ca ratios at the otolith center and edge portions and lower ratios at the middle portion, indicating that this specimen had experience of upstream and downstream migrations. The present study suggests that the yellowfin goby has flexible migration patterns, allowing it to utilize the full range of salinity during its life history.