Biological parameters of a silurid catfish Ompok bimaculatus (Bloch, 1794) from River Ghaghara, India

The present study examined a total of 446 samples of Ompok bimaculatus and describes the condition factor, gonadosomatic index, length-length relationships, sex ratio, size at first maturity. The regression parameter 'b' ranged from 3.06 to 3.76 (r2 > 0.90). During the pre-monsoon, the allometric coefficient 'b' of the LWR was close to isometric value (b = 3.06) while that of overall was positive allometric (b = 3.31) although it suggested positive allometric growth in monsoon (b = 3.21), and post-monsoon (b = 3.76), periods. The values of condition factor ranged from 0.524 to 0.573. In the study, sex ratio ranged from 1:1.03 to 1:1.3. Males ranged from 14.0-26.6 cm while females varied from 11.2-29.0 cm in length. A significant difference in length at 50% maturity (p < 0.05) was found between both the sexes. First maturity stages in males and females were 22.3 cm and 23.2 cm, respectively. The smallest mature female was 22.0 cm L; the largest immature female was 26.8 cm L. The smallest mature male was 20.0 cm L; the largest immature male was 24.5 cm L. The results of the study could be useful to help in sustainable fisheries management in the Ghaghara River.