The investigation on the gastro-somatic index (GaSI) and gonado somatic index (GnSI) of Labeo bata was carried out in spawning season from July to December 2010. Length of fish ranged from 136.11±2.00 to 145.44±0.58 mm and while in average weight was 34.03±1.00 to 44.11±5.29 gm. GaSI and GnSI were determined at different length and weight ranges of different individual fishes. Significantly lowest GaSI was 3.92±0.38 in male specimens, where as 4.50±0.10 in female specimens. GaSI was also determined from wide highest peak ranges of Labeo bata, 8.02±0.06 (November) in male specimens, 7.33±0.10 (October) in female specimens. Ovary weight of the carp ranges from 0.39±0.01 to 1.33±0.58 gm with a mean value of 0.81 gm. Gonado somatic index varied o-in male from 0.73±0.03 to 2.06±0.05 while in female it was 0.91±0.01 to 2.85±0.07. The Gonado-somatic Index (GnSI) varied significantly (P is less than and equal to 0.01) in L. bata as between the sexes and among months. In the present study, it is found that irrespective of season the male Labeo bata is smaller in length and weight in comparison to female.  

 Key words: Gonado Somatic Index; Gastro Somatic Index; Labeo bata; Length; Weight