Effect of season on the fatty acid composition and free amino acid content of the sardine Sardinops melanostictus

The purpose of this study was to clarify the seasonal variation of fatty acid composition and free amino acid content in the Japanese sardine (Sardinops melanostictus) from the sea of Hyuga-Nada, and the relationship between the fatty acid composition of this sardine and that of plankton in the area. The lipid content of sardines at the sea of Hyuga-Nada was low in February (1.8%) and high (7.2%) from July to September. The major fatty acids in the total lipids from sardine were myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), palmitoleic acid (16:1 n-7), oleic acid (18:1 n-9), eicosapentaenoic acid (20:5 n-3), and docosahexaenoic acid (22:6 n-3). The characteristics of the fatty acids isolated from sardines in July were similar to those from plankton in the same season. This reflects the deposition of plankton fatty acids in sardine depot fat. The season of high free histidine content in the ordinary meat corresponded with that of high lipid content. These results suggested that both the fatty acid composition of sardines and the high concentrations of certain amino acids in free form are influenced by the intake and seasonal variation of composition of plankton.