Effects of disinfectants on bacterial load in a commercial fish hatchery in Mymensingh district of Bangladesh

The study was conducted to investigate the effects of four chemical disinfectants salt (NaCl), lime, formalin and potassium permanganate (KMnO4) on bacterial loads in water, eggs and fries in a commercial fish hatchery. Sampling was done in every 10 days interval for each month from March to May. Hatching trays were disinfected using 40 ppm salt water and 20 ppm potassium permanganate. Cisterns (84 ft2 each) were washed and disinfected with combination of lime (5g/ft2) and salt (30g/ft2) followed by application of potassium permanganate (1 ppm) and formalin (0.25 ppm). After disinfecting, bacterial load in hatching tray water reduced immediately than that of overhead tank water. The average highest bacterial load in overhead tank water was 4.89±1.71×107 cfu/ml while the highest load in hatching tray water was 3.30±3.54×106 cfu/ml. The bacterial load of cistern water (1.43±0.75×103 cfu/ml) decreased compared to tank water and gradually increased after six days of giving hormone treated feed. To prevent infection of eggs saline water was applied and lower bacterial load of 4.25±2.67×102 cfu/ml was observed. The study revealed that use of chemical disinfectants in the initial stages of hatchery operation can decrease the bacterial load and thus reduces the chance of occurrence of infection and diseases of eggs and fry.