Utilization of microalgae Schizochytrium sp. in non-fish meal, non-fish oil diet for yellowtail (Seriola quinqueradiata)

Two feeding experiments were conducted to develop non-fish meal and non-fish oil diet for yellowtail with plant protein sources and Schizochytrium meal. For the first experiment, three iso-nitrogenous and iso-lipidic diets were prepared. Control diet was composed with fishmeal and fish oil and the other diet was formulated with plant protein sources and fish oil [FO]. Fish oil in FO diet was totally substituted by rapeseed oil and Schizochytrium sp., which was rich in DHA [NFO1]. Duplicate groups of yellowtails (Seriola quinqueradiata, 190.6 g) were fed the diets for 99 days. NFO1 group showed the lowest palatability and growth. However, fatty acid profile of NFO1 group showed the similar trend to FO. Four non-fish meal diets were prepared for the second experiment with increased amount of feed attractant. 100FO diet was formulated similar to FO diet in the first experiment though higher amount of bonito peptide was contained. The other diets gradually employed Schizochytrium meal to substitute fish oil in 100FO diet for 35, 70 and 100%, respectively [65FO, 30FO, NFO2]. Duplicated groups of yellowtails (186.0 g) were fed the diets for 84 days. The growth result was improved by increasement of bonito peptide; however, it was inversely proportional to employment rate of algae meal. The results suggest possibility for developing non-fish meal diet for yellowtail with plant protein sources and Schizochytrium sp. by inducing enough amount of feed attractant. Moreover, it needs further study on essential fatty acid utilization for yellowtail while developing non-fish meal and non-fish oil diet with microalgae.