The signatures of stable isotopes δ 15N and δ 13C in anadromous and non-anadromous Coilia nasus living in the Yangtze River, and the adjacent sea waters

Abstract

Stable isotopes are increasingly used to investigate seasonal migrations of aquatic organisms. This study employed stable isotopes (δ 13C and δ 15N) 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 13C 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 15N signatures of C. nasus in ZS, CM, and JJ groups were significantly lower than those in PYL group (P < 0.05). Basing on δ 13C and δ 15N signatures, 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 15N but depleted in δ 13C, 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 15N and δ 13C to population assignment studies of C. nasus in the Yangtze River and its affiliated waters. Analysis of stable isotopes (δ 15N and δ 13C) is shown to be a useful tool for discriminating anadromous and non-anadromous C. nasus.