Seasonal variations in major components of Crassostrea gigas from Seto Inland Sea

Abstract

The proximate composition and nutritional content of oysters define their quality and commercial value. Cultivation site and harvest date may impact these characteristics. We assessed moisture, ash, protein, fat, and glycogen concentrations, mineral and free amino acid content, and free fatty acid composition in oysters Crassostrea gigas from three coastal regions of the Seto Inland Sea, Hiroshima, Okayama, and Hyogo, collected throughout the 2013–2014 harvest in Japan. The protein, fat, and ash content of oysters harvested during the same month was similar in all three regions. Moisture content decreased throughout the season, whereas glycogen content increased significantly during the same period and oysters from Okayama and Hyogo regions during March contained glycogen significantly higher than those from Hiroshima. Oysters cultured in Hiroshima had the highest zinc levels during December, January, February, and April. The abundant fatty acids in the oysters cultivated in these areas were eicosapentaenoic acid (EPA) and palmitic acid, and EPA was increased in oysters of Okayama and Hiroshima from November to April. Based on our data, we propose that oyster bed location and harvest date significantly impact the proximate composition and nutrients of oysters.