Fusarium - a new threat to fish population in reservoirs of Kumaun, India.

摘要

F. moniliforme [Gibberella zeae] and F. udum were found to be natural pathogens of freshwater fish in reservoirs in Nanaksagar, India [1994-96], causing mycosis and high mortality in Barbus rana, Channa punctatus, Labeo rohita, Mastaceamblus armatus, Mystus tengra, Puntius sophore and Wallago attu. Both species produced clinical symptoms similar to natural infection in C. punctatus and P. sophore and caused 40-80% mortality under artificial inoculation. Though 9 other species of aquatic fungi belonging to 8 genera of hyphomycetes were also associated with the diseased fish in the reservoir, they were unable to infect the test fish. Fusarium species parasitized fish more commonly during the summer to the rainy season. A temperature >25oC, coupled with relatively low pH (7.1-7.7) and DO (8.3-9.5 mg/litre) encouraged association and infection of these fungi, whereas low temperature during winter (<20oC) adversely affected their colonization on the fish. Mycosis due to aquatic fungi was prevalent during winter-spring, while extra-aquatic fungi dominated during summer-rainy season, thus posing a continual threat to fish in the reservoirs.