Potential dietary influence on the stable isotopes and fatty acid composition of migratory anchovy (<i>Coilia mystus</i>) around the Changjiang Estuary

Abstract

The stable carbon and nitrogen isotopes and fatty acid composition of tapertail anchovy ( Coilia mystus ) at four migration stages collected around the Changjiang Estuary were analysed to investigate the variations in the trophic biomarkers during the fish migration. δ 13 C and δ 15 N values of C. mystus ranged from −21.5 to −15.4‰ and from 6.9–15.8‰, respectively. Both δ 13 C and δ 15 N were enriched during migration. Polyunsaturated fatty acids were the dominant fatty acids and the major fatty acids found in C. mystus were C20:5 n -3, C22:6 n -3, C20:4 n -6, C16:0, C18:0, C16:1 n -7, C18:1( n -9, n -7) and C20:1 + C22:1. Significant changes among C. mystus at different migration stages were found both in the fatty acid composition and specific fatty acid concentration. Though the enrichment of stable isotopes may due to multiple factors (e.g. diet shift, environment and ontogeny), the dietary influence can be determined by the variation in fatty acid composition. Changes in the concentrations of benthic markers (C18:1 n -7 and C20:4 n -6) and pelagic markers (C18:1 n -9 and C20:1 + C22:1) in C. mystus during the migration may suggest that benthic and pelagic food sources alternately dominated the anchovies' diet during different migration stages. It seems that application of multiple biomarkers in the trophic study of migratory fish will elevate the reliability of the analysis.