Stable isotopic composition of otoliths in identification of stock structure of small yellow croaker (Larimichthys polyactis) in China

Abstract

Oxygen and carbon isotope ratios (δ 18O and δ 13C) in otoliths were used to identify the stock structure of small yellow croaker, Larimichthys polyactis. Otoliths were collected from fish at five locations across the Yellow Sea and the Bohai Sea representing most of their distributional range and fisheries areas. The significant differences in the isotopic signatures showed that the five locations could be chemically distinguished and clearly separated, indicating stock subdivision. Correlation of δ 18O and δ 13C values suggested that population of L. polyactis could be divided into the Bohai Sea group, the southern Yellow Sea group and the central Yellow Sea group. Discriminant analysis of δ 18O and δ 13C values demonstrated a high significant difference with 85.7% classification accuracy. The spatial separation of L. polyactis indicated a complex stock structure across the Yellow Sea and the Bohai Sea. These results indicate that optimal fisheries management may require a comprehensive consideration on the current spatial arrangements. This study has provided further evidence that measurement of the stable isotopes ratios in otolith can be a valuable tool in the delineation of fishery management units.