Spatial and temporal variations of the trophodynamics of anchovy (Engraulis japonicus) in the southern coastal waters of Korea using fatty acid trophic markers

Abstract

The abundance and proportion of specific fatty acids differ among fundamental groups of lower trophic levels. Some prey fatty acids are transferred directly to predators. In this study, fatty acid compositions of juvenile, young, and adult anchovies (Engraulis japonicus) were evaluated as trophic markers for feeding environments in four regions (Tongyeong, Namhaedo, Yeosu, and Jindo) of the southern coastal waters of Korea. The condition factor (CF) increased with advancing life stage, and the gonad somatic index (GSI) peaked in May. C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C20:1n-9, C20:5n-3, and C22:6n-3, among other saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) were predominant in all life stages. We observed geographic eastward and life-stage dependent trends wherein C14:0, C16:1n-7 C18:1n-9, and C20:5n-3 fatty acids increased, while C22:6n-3 decreased during development from juvenile to adult in most season. Indicating Calanus copepod trophic markers, MUFA 20:1n-9 and 22:1n-9, were high in the upwelling area of the southwestern sea, but low in southern coastal areas. High MUFA 18:1n-9 and SFA 16:0 in all areas suggests a significant dietary input from non-calanoid copepods in the southern coastal waters of Korea. High dependence on dinoflagellate harmful algal blooms (HABs) was detected in the ratios of major fatty acids (C20:5n-3/C22:6n-3 and C16:1n-7/C16:0) in juvenile and young fish. These results indicate that life stage- and area-specific fatty acid compositions may be explained by regional feeding environments, which influence juvenile and young fish growth and adult maturation in the southern coastal waters of Korea.