The Signatures of Stable Isotopes δ~(15)N and δ~(13)C in Anadromous and Non-Anadromous Coilia nasus Living in the Yangtze River, and the Adjacent Sea Waters The Signatures of Stable Isotopes δ~(15)N and δ~(13)C in Anadromous and Non-Anadromous Coilia nasus Living in the Yangtze River, and the Adjacent Sea Waters

Stable isotopes are increasingly used to investigate seasonal migrations of aquatic organisms. This study employed stable isotopes(δ~(13) and δ15N) for Coilia nasus from the lower Yangtze River and the adjacent East China Sea to distinguish different ecotypic groups, ascertain trophic nutrition positions, and reflect environmental influences on C. nasus. δ~(13)C signatures of C. nasus sampled from Zhoushan(ZS), Chongming(CM), and Jingjiang(JJ) waters were significantly higher than those from the Poyang Lake(PYL)(P < 0.05). By contrast, δ~(15)Nsignatures of C. nasus in ZS, CM, and JJ groups were significantly lower than those in PYL group(P < 0.05). Basing on δ~(13) and δ~(15)Nsignatures, we could distinguish anadromous(ZS, CM, and JJ) and non-anadromous(PYL) groups. The trophic level(TL) of anadromous C. nasus ranged from 2.90 to 3.04, whereas that of non-anadromous C. nasus was 4.38. C. nasus occupied the middle and top nutrition positions in the marine and Poyang Lake food webs, respectively. C. nasus in Poyang Lake were significantly more enriched in δ~(15)N but depleted in δ~(13), suggesting that anthropogenic nutrient inputs and terrigenous organic carbon are important to the Poyang Lake food web. This study is the first to apply δ~(15)Nand δ~(13) to population assignment studies of C. nasus in the Yangtze River and its affiliated waters. Analysis of stable isotopes(δ~(15)Nand δ~(13)) is shown to be a useful tool for discriminating anadromous and non-anadromous C. nasus