Investigation of the geographical origin and migration of anchovy Engraulis japonicus in Tachibana Bay, Japan: A stable isotope approach

摘要

We investigated the geographical origin and migration of anchovy Engraulis japonicus in Tachibana Bay, western Japan, using carbon and nitrogen stable isotope ratios (delta C-13 and delta N-15, respectively). Stable isotope ratios of anchovy varied among seasonal samples for both delta C-13 and delta N-15. In particular, the delta C-13 values were clearly segregated; winter samples showed higher values (delta C-13>-17.5 parts per thousand) than spring samples (delta C-13<-18.2 parts per thousand). Moreover, these differences corresponded to the geographical variations in previously reported stable isotope ratios for anchovy; higher values in winter corresponded to the values of inshore habitat and lower values in spring corresponded to those of the offshore habitat. Therefore the spring population is considered to have originated from the offshore region and recently migrated to the sampling regions, while the winter population would have experienced the inshore region over an extended period. Our results support the general concept of the migration of anchovy populations deduced by the fishermen of Tachibana Bay.