Impact of epizootic ulcerative syndrome (EUS) on the biodiversity of Nandus nandus and Puntius sophore in Beel fisheries of Bangladesh

An experiment was carried out for a period of eleven months from March 2012 to January 2013 in order to observe the effect of epizootic ulcerative syndrome (EUS) on the biodiversity status of Nandus nandus and Puntius sophore in two beels of Kailla and Dighli are situated in Ishwargonj upazilla of Mymensingh district. All the water quality parameters were within the suitable range during the experimental period except temperature and hardness. Fishes were examined clinically and histopathologically. By clinically examined, it was observed that fishes were more affected from October to January having red spots, ulcer, scale loss and fin rot. Almost normal in appearance was observed during the months from March to October in fishes of both the beels under clinical and histopathological observations. Marked pathological changes like fungal granuloma, necrosis, haemorrhages, vacuums, fat droplets, pyknosis and hyperplasia were observed in the months of November, December and January. Fungal granuloma was observed in skin, muscle and kidney of N. nandus and only in skin and muscle of P. sophore. In FGD, fishermen of both the beels mentioned that EUS was the most significant disease especially during the colder months i.e., November, December and January. Fishermen could easily recognize EUS clinically and according to them the disease accounts about 80-90% in Kailla beel and 75-80% in Dighli beel. Moreover, in histopathological observation, it could be mentioned from farmers opinion (FGD) that diseases especially EUS has significant effect in the reduction of SIS (small indigenous species) from open water bodies of both the beels. According to fishermen opinion, some SIS were reduced to almost half in comparison to a decade ago in both the beels.