<b>Study on Sex Ratio and Gonadosomatic Index of Fresh Water Fish C. Gachua Ham.1822 </b> Aspect of reproductive biology of fresh water murrel C. gachua, such as sex ratio and Gonadosomatic Index were investigated from the pools ,ditches and even from river Ganga in and around the area of Bhagalpur, Bihar for a complete year span. On the basis of the monthly variation, the overall sex ratio was recorded 1 1.22 M F . The spawning season extends from June to August. Gonadosomatic Index in female fish reaches maximum in May with 44.50 . The GSI recorded minimum in September with 5.71 followed by Oct with 7.21 .GSI in male C. gachua was also studied and found the maximum in the month of June with 4.86 , closely followed by the month of July with 4.06 . The GSI was found the minimum in the month of January with 0.57 closely followed by the month of February with 0.84 . GSI, Spawning, Sex ratio 19-22 Issue-3 Volume-6 Navjyoti Ranjan Verma