Even though fish and fisheries are pivotal in meeting the food security and sustenance of people, in most countries diseases outbreaks have threatened profitable and viable operations throughout the world. Fungal infections are second only to bacterial diseases in economic importance. Among the fungi, Achlya species appear to the most virulent among Saprolegniales. Hence the present study was aimed at assessing their presence and their effect in different aquatic systems in Pudukkottai District of Tamil Nadu. Of the total 314 fishes chosen, a total of 63 species were found with mycotic infections. The percentage of infection was found to vary from 15.3 to 38.09% examination of carps showed they had multiple infections. Among the nine species of fish examined, Channa striatus was the most prone to infection of Achlya species.