Geographical variations in genetic group composition, life-history traits, and statolith shape for Sepioteuthis spp. in the Northwest Pacific

Abstract

Context. Sepioteuthis cf. lessoniana is widely distributed in the coastal waters of the Indo-Pacific region and is a crucial fisheries resource along its distributional range. At least four lineages of Sepioteuthis have been identified in the western Pacific region; however, their biological information remains unclear. Aims. In this study, the genetic groups of Sepioteuthis spp. in the southwestern Japan and northern Taiwan was examined using molecular markers, and the life-history traits and statolith morphology of the genetic groups were investigated. Methods. A total of 137 and 205 squid individuals from Japan and Taiwan, respectively, were examined. Key results. Three genetic groups of Sepioteuthis (S. sp. 1, sp. 2, and sp. 2A) were identified based on molecular evidence in both areas, among which Sepioteuthis sp. 2 was dominant in Japan (87%), whereas Sepioteuthis sp. 1 was dominant in Taiwan (70%). For the same genetic group, the mantle length, average growth rate, and size and age at maturity were greater for the squid in Japan than those in Taiwan. The statolith exhibited a wider lateral dome and longer rostrum for the squid in Taiwan than those in Japan. Conclusions. This study indicated the variations in the life-history traits and statolith shapes of the squid were greater between geographic populations (Japan and Taiwan) than among the genetic groups, which suggested that environmental effects on life-history traits and statolith shape of squid were greater than genetic effects.