[Element composition in the statoliths of Sthenoteuthis oualaniensis squid in Xisha islands waters of South China Sea]

Sthenoteuthis oualaniensis is the most important cephalopods fishery resource of the South China Sea, which supported the falling-net fishery of Guangdong, Guangxi and Hainan Provinces of China. Understanding the fisheries biology is essential for sustainable exploitation and management of this squid. Statolith is one of the most important hard tissues of cephalopods which were widely used in the research of fisheries biology and ecology. Elements of 20 statoliths of S. oualaniensis collected in the Xisha islands waters of South China Sea during May to August by the falling-net fishery of 2017 were analyzed with Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for different sexes, different hatching groups, and history stages. The results showed that the statolith of the S. oualaniensis contained 55 elements, with calcium (Ca), strontium (Sr), sodium (Na), phosphorus (P), silicon (Si),magnesium (Mg), potassium (K), iron (Fe), barium (Ba) and boron (B) being the top ten abundant elements. The analysis of variance (ANOVA) showed that there was no significant difference in all element distributions between sexes for the most abundant ten elements. Significant differences existed in the contents of Si, Sr, Mg, Na and K but no significant difference was found in the contents of Ca, P, B, Fe and B between different hatching groups. There were significant differences in the contents of Sr, Na, P, K, Si, Mg, B and Ba, but no significant difference in the contents of Ca and Fe in the statoliths among different growth zones. Our results suggested that Sr, Na, K and Mg were probably the best four elements for life history reconstruction and examining population structure of the S. oualaniensis.