A 8-week growth trial was conducted to determine the quantitative dietary lysine requirement for juvenile Sebastes schlegeli Semipurified diets were formulated to be isonitrogenous and isoenergetic (48.50% crude protein and 18.04kJ/g gross energy) Crystalline L-amino acids were use to provide part of dietary protein. The amino acid pattern except lysine of the muscle protein of Sebastes schlegeli was used as reference. Six diets were formulated to contain 15.4, 20.4, 25.4, 30.4, 35.4 or 40.4g lysine kg(-1) dry matter. The experiment was conducted in triplicates in 84-1 indoor flow-through circular conical tanks at 19.5 +/- 0.5 degrees C and 30 parts per thousand - 34 parts per thousand salinity. The results showed that dietary lysine level significantly affected weight gain ( WG), food conversion ratio ( FCR), protein retention efficiency ( PREI) and activity of serum glutamic-oxalacetic transaminase (AST) and glutamic-pyruvic transaminase (ALT). With increase in dietary lysine level, weight gain increased while highest value was observed at 3.54% dietary lysine level. Protein retention efficiency was lower in the fish fed the basal diet ( P < 0.05). Food conversion ratio decreased with increasing dietary lysine and showed lowest value at 3.54% dietary lysine group( P < 0.05). No significant difference ( P > 0. 05) was found in feeding rate ( FR), energy retention efficiency ( ERE), hepatosomatic index (HSI), content of serum triglyceride and cholesterol, body composition of protein, lipid, ash, dry matter and energy. By regression, the optimal dietary lysine requirement for maximum growth of Sebastes schlegeli was 2.99% of dry matter of 6.16% of protein.
