Migration routes of the swordtip squid Uroteuthis edulis in the East China Sea determined based on the statolith trace element information

Uroteuthis edulis (Hoyle, 1885) was one of the important loliginid squid resources in the East China Sea. This species has a complex population structure and a wide range of migration. Statolith trace elements were widely used in the study on individual life history and the reconstruction of habitat. In this study, the trace elements in the statoliths of the four seasons cohorts of U. edulis in the East China Sea were determined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The clustering analysis on the trace element ratios in different growth stages was carried out with Euclidean distance method and the optimal relationship between trace element ratios and water temperature was established to predict and calculate the areas and probability of potential habitats. The ratios of Mg:Ca, Sr:Ca, and Ba:Ca in each stock firstly decreased, then increased, and reached the minimum values in the sub-adult stage. The spring and winter stocks were clustered into one group, whereas the summer and autumn stocks were clustered into one group. There were significant differences in the ratios of Mg:Ca, Sr:Ca, and Ba:Ca among the clustering group ( P < 0.05). The calculation results of the models indicate that hatching water temperatures of the winter–spring and summer–autumn stocks were, respectively, 19.34 to 23.91°C (55 m) and 15.91 to 19.43°C (25 m). The winter–spring stock hatched in the waters of northeastern Taiwan and the paralarva migrated to the northeastern seas along the Kuroshio Branch Current in the western continental shelf of the East China Sea and the Taiwan Warm Current. The summer–autumn stocks hatched in the waters of Zhoushan, Zhejiang of China, and the paralarva migrated to the central East China Sea under the influence of the Yangtze River, and then followed the Taiwan Warm current to reach the northeastern waters for feeding migration. This study provides the basis for revealing the migration mechanism and strategy of U. edulis .