Fatty Acid Profiles in Tissues of Japanese Eel (Anguilla japonica) from the Yangtze Estuary and Adjacent Offshore Waters: A Comparative Analysis

To compare the fatty acid composition in different tissues of Anguilla japonica before and after sea entry, we analyzed the muscle, liver, and ovary of eels from the Yangtze Estuary and offshore waters, and describe the distribution patterns of various fatty acids in different tissues. Comparing different tissues, in eels from the estuary, the muscle had the highest content of EPA, the liver had the highest content of DHA, and the ovary had the highest contents of ARA. In offshore eels, the muscle had the highest contents of C16:1 and C18:1n9c; the liver had the highest content of C16:0; and the ovary had the highest contents of C18:0 and DPA3. Comparing eels before and after sea entry, the contents of C14:0, C16:0, C20:1n9 and C20:2 in the ovary of estuary eels were significantly higher than those in the offshore eels. Conversely, the contents of C18:0, C20:0, DPA3, HUFA, total n3-PUFA and n3/n6 ratio in the ovary of offshore eels were significantly higher than those in estuary eels. Ovaries of estuarine eels showed higher proportions of saturated fatty acids, whereas ovaries of offshore eels showed higher proportions of n3-PUFA. The observed differences in ovarian fatty acid profiles may reflect the nutritional demands associated with gonadal development stages, which were determined by histological oocyte staging.