Epizootic infection due to Achlya debaryana in a catfish.

Achyla debaryana (Saprolegniales, Oomycetes) is being reported for the first time as a fish pathogen, causing an epizootic of mycosis in a catfish, Mastacembelus armatus, in Nanak Sugar, a huge artificial reservoir and recognized fish production centre in Naini Tal district, Uttar Pradesh, India. The incidence of infection was found to be influenced by the physicochemical characteristics of water. The maximum disease severity (52 and 47.4%) occurred in March with moderate water temperature (22-24 degrees C), high dissolved oxygen content (9.5 mg l-1) and pH 8.6, while the lowest level of infection (3 and 1.8%) was recorded at high temperature (29-32 degrees C) during June.