This study reports on various biological features-sex ratio, Length-Frequency Distributions (LFDs), Length-Weight Relationships (LWRs) as well as condition factors of Gangetic leaf fish, Nandus nandus from the floodplain wetlands of upper Brahmaputra basin, Assam, NE India. For LFDs, no significant differences of sizes observed between the sexes and 10-12 cm being the most dominant length group for both the sexes of the species. In case of sex ratio, the females significantly outnumbered the males in all the seasons except pre-monsoon. The LWRs showed positive allometric growth except in winter season. All the relationships between total length and total weight are found to be highly significant (p<0.01). The calculated b values ranged from 2.961(post-monsoon) to 4.124 (winter) for males and from 3.101 (winter) to 3.538 (post-monsoon) for females. Calculated mean value of relative Condition Factor (Kn) ranges between 1.00 and 1.07 with minimum seasonal variations for both the sexes while mean value of Fulton’s Condition Factor (K) is found to be slightly higher in females than males for major part of the study.
