Observation on the Biochemical Constituents of Threadfin Bream Nemipterus japonicus during Gonad Maturation from Suez Gulf, Red Sea, Egypt

Abstract

The present study revealed that the biochemical constituent with respect to different maturity stages of Nemipterus japonicus fish is associated with reproductive cycle, storage and utilization of reserves. Gonadosomatic index N. Japonicus recorded high values (3.5 and 0.51) in May and low values (0.4 and 0.25) in February for female and male, respectively. The maturity stages was classified into 5 maturity stages as follow, 1) immature stage, 2) maturing stage, 3) mature stage, 4) ripe stage and 5) spent stage. The spawning season of N. japonicus extend from May to September. The biochemical composition in muscle, liver and gonad in both sexes are found higher in early stages of maturity and decreases during gonad maturation. The muscle had more fat and crude protein content during the immature stage. Early stages of maturation, hence offer greater food value in these species. With the advancement of maturity, a drop in the fat and soluble crude protein was observed, whereas a linear relationship with moisture was noted from immature to mature stage. The composition of muscle always demonstrated an inverse relationship with hepatic and gonadal composition. Highest crude protein percentage was in stage IV (72.0 ± 2.22) in ovary. The total crude lipid percentage of the ovary showed a gradual increase from Stage I (5.1 ± 0.47) to Stage IV (21.8 ±1.02).