Study on effects of different concentrations of vitamin C and hardness at brood-stock tank water on reproductive indices of freshwater prawn (Macrobrachium rosenbergii) in recirculation system

Optimum concentration of vitamin C and hardness at giant freshwater prawn brood-stock tank water has great important on their reproductive quality in recirculation system. The main objective of the present study is investigation on effects of different concentrations of these factors on reproductive parameters of the giant freshwater prawn female brood-stock. For this purpose, at the first experiment, treatments with different concentrations of vitamin C including 0 (Control treatment), 2, 5, 8 and 10 ppm and for the second experiment treatments with different concentrations of hardness including 205 (Control treatment), 250, 300, 350 and 400 ppm were prepared at the brood-stock tanks and their influences were evaluated on reproductive indices of freshwater prawn after 3 reproductive cycle. According to the results, optimum concentration of water hardness and vitamin C were assessed 250 and 5 ppm respectively in the brood-stock tanks. Also the results indicated that the studied factors showed significant differences (P˂0.05) in egg dry weight, fertilized eggs percentage, hatched eggs percentage and ESI (Egg-clutch Somatic Index) parameters among the treatments but did not differ significantly in total and relative fecundity parameters (P˃0.05). It is concluded that studied elements have not any influences in oogenesis process and show their effects during vitellogenesis and embryogenesis periods.