The Effect of Inland Saline Groundwater on Growth, Maturation, and Osmoregulation of Common Carp

A 90-day experiment was conducted on Common Carp Cyprinus carpio in eight rectangular earthen ponds (21 x 10 x 1.50 m) for testing the effect of four groundwater salinities (0, 5, 10, and 15 parts per thousand). At the end of the experiment, 100% survival was observed in all of the treatment groups. Somatic growth and reproductive performance were significantly (P < 0.05) influenced by salinity. Both males and females showed a significantly higher gonadosomatic index (24.46 +/- 4.11% [mean +/- SE]) at 5 parts per thousand (P < 0.05) compared with the fish that were kept in freshwater (15.92 +/- 2.43%). The gonadal osmolality and osmolytes of the seminal and ovarian fluids increased in proportion to salinity. Ova diameter was inversely related to salinity. The incidence of spawning at 5 parts per thousand was significantly higher than at 0, 10, and 15 parts per thousand. The gonadosomatic index was also significantly higher (30.15 +/- 3.44%) at 5 parts per thousand followed by 0, 10, and 15 parts per thousand, respectively. We concluded that the optimum salinity for the maturation of Common Carp is 5 parts per thousand.