Schizochytrium as a replacement for fish oil in a fishmeal free diet for jade perch, Scortum barcoo (McCulloch & Waite)

A 10‐week trial was conducted to determine the response of juvenile jade perch Scortum barcoo on the replacement of dietary fish oil (FO) in a fishmeal free diet. Three iso‐nitrogenous, isocaloric and isolipidic diets were formulated, each containing a different primary fat source: FO, linseed oil (LO), and a mixture of Schizochytrium and LO. The substitution of FO with the mixture of Schizochytrium and LO did not cause a difference in growth. However, there was an 8% reduction in weight gain in fish fed dietary LO, indicating that juvenile jade perch do require a minimal concentration of dietary n‐3 highly unsaturated fatty acids (HUFA). Fish fed the Schizochytrium diet stored more efficient n‐3 HUFA and in particular DHA in their flesh, and retained a higher fillet recovery compared to fish fed FO. In addition, we demonstrated that jade perch are able to produce both n‐3 HUFA and n‐6 HUFA when dietary PUFA are present. Fish fed the LO diet for 10 weeks contained the lowest amount of n‐3 HUFA in fillets among dietary treatment groups. However, feeding these fish the Schizochytrium diet for an additional 4 weeks increased the n‐3 HUFA content towards the same concentration of n‐3 HUFA found in the flesh of fish fed FO, without affecting the sensory properties of the fillets. In contrary, feeding the Schizochytrium diet for a continuous period of 14 weeks lowered overall sensory property scores.