Effects of Various Sodium Adsorption Ratio (SAR) at Brood-Stock Tank Water on Reproductive Performance of the Female Freshwater Prawn (Macrobrachium rosenbergii)

Water quality management in brood-stock tanks, especially in terms of water salinity and water hardness, is of great importance to the reproductive performance of the crustaceans. The sodium absorption ratio (SAR) is a compound formula that has a ratio of sodium ion to total calcium and magnesium ions of water. The purpose of this study was to investigate the effects of different ratios of sodium to total calcium and magnesium of (SAR) in water on reproductive indices of female freshwater prawn. For this study, 12 tanks of 80 liters were assigned to 4 treatments with 0, 5, 10 and 15 sodium absorption ratios, each with 3 replicates. After the 60-day period of experiment, different reproductive indices were measured. The results indicated that the egg clutch somatic index (ESI) and the dry weight of eggs were significantly higher in treatment of sodium absorption ratio 5 than other treatments. Fertilized eggs percentage and hatched eggs percentage in control and 5 treatments were not significantly different but decreased with increasing of sodium absorption ratio in 10 and 15 treatments respectively. While different levels of sodium absorption ratio in water had no significant effect on total and relative fecundity parameters. Larval status index was significantly higher in treatment of sodium absorption ratio 5 than other treatments. Finally, the SAR at female brood-stock tank water can be optimized to achieve the highest reproductive performance and produce the best quality larvae. Therefore, it is recommended that the authorities of the reproductive centers that do not have natural brackish-water should adjust the water absorption ratio to 5 when making brackish-water for hatchery centers.