Stable isotope analysis of the gladius to investigate migration and. trophic patterns of the neon flying squid (Ommastrephes bartramii)

The neon flying squid, Ommastrephes bartramii is broadly distributed in subtropical and temperate regions of the world's oceans. The North Pacific population is comprised of two spawning cohorts; the autumn cohort and winter-spring cohort, which despite their apparent contiguous hatching periods, have marked differences in the mantle length between the two cohorts, indicating differences in behavior. Especially, females of the autumn cohort after remaining in the subtropical zone for spring, in the first half of the summer migrate close to the vicinity of the southern boundary of the transition area. Subsequently they migrate into the subarctic waters to feed. However, for males details are less clear and it is considered that they remain in the subtropical zone without migrating to the subarctic feeding area. However little is known about the migration strategy of O. bartramii. Stable isotope profiles along the gladius (internal chitinous shell) have been recently analyzed and form a promising tool to back-calculate a chronological record of changes in the diet and habitat. In this study, delta C-13 and delta N-15 values were measured along the gladius to reconstruct the feeding variations and habitat of the autumn cohort during ontogeny. The results of delta C-13 values support previous studies which inferred differences in migratory behavior between males and females. These differences occurred from 260 mm mantle length. (C) 2015 Elsevier B.V. All rights reserved.