Otolith Shape Analysis and its Utilily for Identification of Two Smelt Species, Hypomesus japonicus and H. nipponensis (Osteichthyes, Osmeridae) from the Northwestern Sea of Japan with Inferences in Stock Discrimination of H. japonicus

Abstract

In this study, otolith shape analysis has been used to perform identification of two smelt species specimens (genus Hypomesus), H. japonicus and H. nipponensis, as well as differentiation of local gatherings in the first species, in the north-western Sea of Japan (SJ). Based on the otolith shape and using several multidimension statistical approaches obvious differences were defined for both inter- and intraspecies levels of otolith variation. Species discrimination by otolith shape indices and other variables extends well to within the species H. japonicus gatherings, the individuals sampled from the northern sample in Olga Bay (OB) are most similar morphologically to those from the coastal waters off the village of Terney to the north of OB. In contrast, the individuals of this species from the coastal waters off Russky Island (RI), including another southern sample and those from northern samples, manifest the greatest differences, thus providing evidence on the existence of at least two local stocks of the species in the waters of the north-western Sea of Japan.