Comparative study on the nutrient composition, amino acids, and fatty acids composition of glass eel tissues of Japanese eel (Anguilla japonica) from offshore of China

In order to understand the nutritional requirements of Japanese eel (Anguilla japonica) larvae, the nutrients composition, amino acids and fatty acids were determined in the tissues of migratory glass eel from 6 different locations in the offshore of China. The results showed that the moisture content was 78.62%±2.03%, and the crude protein content, the crude fat content and the crude ash content were 69.08%±0.64%, 11.96%±1.33% and 11.45%±1.30%, respectively on a dry weight basis. No significant difference in moisture content from different sampling sites was observed. Samples from Zhoushan site had the highest crude protein content and the lowest crude fat content, which was significantly different from other sampling sites. Meanwhile, visible contents were found in the fish intestine from Zhoushan samples. In different migration locations, the amino acids with the highest content included glutamic acid, aspartic acid, lysine and leucine; while cysteine was the lowest. However, the only significant difference of amino acids content was found in samples from Zhoushan site. The C16:0, C18:1n9, C20:5n3 (EPA), C22:5n3, C22:6n3 (DHA) were the main components in samples from different sampling sites. The EPA and DHA accounted for 31.59%±1.00% of the total fatty acids, and the essential fatty acids contents were significantly different among samples from various sampling sites. Studies have shown that the theoretical requirements of essential amino acids and fatty acids were higher in the feed of larvae fish, which implied that both were important for the growth of glass eel. By comparing the nutrient composition of different sites and the theoretical feed requirements, it suggested that the marine environment at Zhoushan site contained more suitable food for glass eel, and further research is still needed to study the open bait for eel.