SEASONAL VARIATION OF GILL, SKIN, MUSCLE, LIVER AND KIDNEY PATHOLOGY OF MRIGAL (Cirrhinus cirrhosus) IN CULTURAL POND FISHERIES, MYMENSINGH, BANGLADESH
An investigation on the seasonal variation of gill, skin muscle, liver and kidney pathology of Mrigal (Cirrhinus cirrhosus) was carried out from four Government (Govt.) and four Private (Pvt.) fish farms, Mymensingh, Bangladesh during June, 2010 to May, 2012. Fish sampling and water quality parameters were monitored monthly basis. For histopathological studies skin, muscle, gill, liver and kidney were collected, processed and stained in Haematoxylin and Eosin. Histologically, Mrigal of different fish farms were more affected in colder months. All the investigated organs of Mrigal were exhibited few abnormalities during summer, however, mild hyperplasia, haemorrhage, partial loss of secondary gill lamellae, marked and hypertrophy was observed during the rainy season. Several pathological changes like necrosis, fungal granuloma, protozoan and monogenean cyst, vacuolation, melanomacrophase, haemorrhage, hypertrophy, hyperplasia and clubbing were recorded in all the investigated organs. Among them fish gills and skin were more affected followed by liver and kidney. In some cases, large bacterial colony and protozoan cyst were observed in the secondary gill lamellae of Mrigal. The ectoparasites were very common in gills and skin of all fishes. Water quality parameters were taken and management practices were investigated fortnightly interval in different farms. These were almost similar for all experimental ponds. The risk of being infestation by parasites of carp significantly (p<0.001) increased when the water quality parameters such as temperature, dissolved oxygen, pH, ammonia, hardness, alkalinity, transparency and depth of water etc. were not maintained the optimum level.