i he present study reveaied that the chronic exposure (3 weeks) to subleth al concentrations (0.3 and 0.6 ppm) of the aquatic herbicide Acrolein which is considered as a drastic stress factor on Boltifish Oreochromis niloticus when subjected to the experimental infection with Aeromonas hydrophila intraperitoneally leading to high morbidity (with typical septicem ic lesions) and mortality rates in comparison to the un-exposed fish to pollution.