The study was carried out to determine length-weight relationship and sex ratio of a freshwater fish Amblypharyngodon mola (Hamilton 1822) collected from Dekar haor of Sunamganj district during the period of January to August 2017. A total of 2000 fishes were collected for the study and categorized these fishes into three groups namely males, females and combined sexes. Among 2000 mola 777 were male and 1223 were female. Length-weight equations and the correlation coefficients obtained for males, females and combined ones were: males Y = –1.97 + 3.00X, r = 0.883; females Y = –2.30 + 3.41X, r = 0.914 and combined Y = –2.11 + 3.16X, r = 0.904. Female’s A. mola attained more weight with the increases in length. Value of correlation coefficient ‘r’ was 0.883 for male and exhibited highly positive correlation between length and weight. On the contrary, ‘r’ value for female was 0.914 and it had also strongly positive correlation between length and weight relationships. Length-weight relationship of A. mola for male, female and combined sexes showed allometric pattern of growth. Condition factor ‘K’ for male, female and combined sexes was 1.09, 1.05 and 1.06, respectively and indicated better condition of fishes. The highest sex ratio (1 : 2.05) was found in May and the lowest (1 : 1.33) was in February. Dominance of females over males throughout the year was observed with an average ratio of male and female 1 : 1.57. Therefore, results of the study indicate that the existing hydrobiological conditions of the haor are conducive for food availability, free movement, feeding and better growth of the fish. Asiat. Soc. Bangladesh, Sci. 44(2): 185-193, December 2018

To assess the effect of probiotics on growth, survival rate and production performance of all monosex tilapia (Oreochromis niloticus) for a period of 120 days in 2016 in nylon net cages placed in Dekar haor of Sunamganj district. The study was categorized into four treatments as T1 (brand a), T2 (brand b), T3 (brand c) and T4 (control) based on probiotics and each having three replicates. Cages were stocked with nursed male tilapia fry at a density of 35 nos./m3 with average size of 14.33 ± 6.41 - 16.33 ± 3.15 g. Tilapia of all the cages were fed with commercial mega floating feed at a decreasing rate of 10 - 5% of total biomass thrice daily. Feed was supplemented with probiotics at a rate of 0.5 g/kg. Comparatively higher growth (307.33 ± 33.92 g), survival rate (97.6 ± 4.90%), yield (10.5 ± 1.15 kg/m3), net profit (Tk.798.96 ± 90.85/m3) and lower food conversion ratio (1.16) were secured in T3 than that of other treatments, which were manifolds higher than the earthen freshwater and brackish waterbodies. Therefore, results of the study reveal that probiotics may be used in aquaculture for increasing fish production. Asiat. Soc. Bangladesh, Sci. 44(1): 69-78, June 2018