206-215The composition and temporal distribution of the postlarval and juvenile fishes in five river systems of Sundarbans mangrove water with different salinities were studied. Monthly or fortnightly day time sampling was conducted with a rectangular drag net. Thirty seven species of fish belonging to 27 families were recorded during the 2 years study. Panchax melastigma, Liza parsia, L. tade and Gobiidae were the most abundant fish species/taxa. In the Sundarbans, species diversity and abundance gradually decreased from the freshwater zone to the saline zone. The highest monthly density of 13 species was observed in the Passur river during November. Liza spp. was the most abundant juvenile catch constituting 29.32%, followed by a small fish P. melastigma (20.13%) and Gobiidae (12.98%). No significant variation in abundance of fish species was observed with lunar cycle, although the annual peak was recorded in winter. Fish abundances varied significantly (p<0.05) among months and rivers. Water temperature and salinity were correlated with the most abundant species