Effect of n-3 and n-6 fatty acids in broodstock diet on reproduction and fatty acid composition of broodstock and eggs in the Japanese eel Anguilla japonica

Abstract This study investigated the effect of n-3 to n-6 fatty acid ratios in broodstock diets on reproduction and fatty acid composition of broodstock and eggs of the Japanese eel. Broodstock were fed with a commercial diet supplemented with various lipids for 3 months before induction of maturation. The supplemental lipids were prepared by a combination of corn oil and pollack oil (corn oil alone (CO); corn oil:pollack oil = 1:1 (MX); pollack oil alone (PO)). Weight gain of broodstock during the feeding trial was slightly lower in fish fed PO compared to the other two groups, but the differences were not significant. Buoyant egg rate and fertilization rate in the CO group were higher than the other two groups. However, the lowest hatching rate was found in the CO group. Fatty acid composition of diets affected the composition of broodstock and egg fatty acids, in particular arachidonic acid (AA) and eicosapentaenoic acid (EPA) levels. Elevated levels of the corn oil supplementation significantly increased AA level and decreased EPA level in polar lipids. In contrast to AA and EPA, there was no notable effect of dietary lipids on docosahexaenoic acid (DHA) level. The present study suggests that both n-3 and n-6 fatty acids are necessary for reproduction as well as growth of eel broodstock, and a higher ratio of n-6 to n-3 fatty acids negatively affected embryogenesis.