Element Signature in Otolith Nuclei for Stock Delineation of Anadromous Tapertail Anchovy Using Laser Ablation ICPMS

Element signature in otolith nuclei was determined using laser ablation ICPMS for stock delineation of anadromous tapertail anchovy (Coilia nasus) in five Chinese estuaries. A total of five elements (Na, Mg, K, Sr, Ba) were detected in the otolith nuclei of the adult tapertail anchovy. The analytical accuracy for the NIST standard averaged across all samples was high for all the five elements with %RSD ranging from 2.55 (Na) to 4.65 (Mg). LODs (mmol mol^-1) for Na, (0.127), Mg (0.0017), K (0.107), Sr (0.0046), and Ba (0.0002) were all well bellowed the detected concentrations in the otoliths. Results showed that elemental composition in the otolith nuclei of adult tapertail anchovy varied substantially among river estuaries but maintained relatively stable in a specific estuary over a short time period of 3-4 years. Trace element signatures, particularly the concentration ratios of Sr:Ca and Ba:Ca, were distinct enough to be used as effective natal tags for discriminating among tapertail anchovy populations. They could efficiently discriminate the Liaodong bay (84.6%), the Yellow River Estuary (84.6%), and the Yangtze River Estuary (80.0%) samples from others, followed by the Bohai bay (66.7%) and the Jiaozhou bay (61.5%) samples.. An overall classification accuracy rate of 75.8% of the discriminant functions generated from trace element signatures indicated that they appeared to have potential for reflecting the element signatures of their natal rivers. Moreover, the pronounced difference of elemental composition observed in the otolith nuclei between the 1985 and 2008 samples in the Yangtze River Estuary indicated a drastic shift of their chemical environmental history over the past two decades. Element fingerprinting was thus an effective tool to delineate populations of this anadromous fish in the estuarine areas along the Chinese coast.