The serological and molecular approaches have clearly established the emergence of WNV in West Bengal. Hence, for proper case management, detection of WNV in common febrile illness is strongly recommended.

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An investigation was carried out on the limnological aspects of Ashura beel at Dinajpur district in Bangladesh. Several limnological parameters were evaluated from March 2013 to October 2013 from three sampling sites namely Kajladoho, Burirdoho and Sonnasydoho. Physical, chemical and biological parameters were analyzed fortnightly both at the field level and departmental laboratory of Fisheries Management, Hajee Mohammad Danesh Science and Technology University, Dinajpur. Findings revealed that only water level in three sampling sites varied significantly. The ranges of water temperature, transparency, water level at three sampling sites were 24 to 35.50°C, 17 to 27.50 cm and 0.58 to 2.44 m, respectively. Moreover, the dissolved oxygen concentration, pH, total alkalinity, total hardness and phosphate-phosphorus concentration were also remained within optimum ranges. Thirty four genera were recorded where phytoplankton includes 29 genera belonging to four groups such as euglenophyceae, cyanophyceae, bacillariophyceae and chlorophyceae and five genera of zooplankton in the four groups namely copepoda, rotifera, cladocera and crustacean larvae. Phytoplankton was dominated by chlorophyceae and zooplankton dominated by copepoda. The abundance of phytoplankton was positively correlated with water temperature, water level, dissolved oxygen, alkalinity, hardness, pH, and phosphate-phosphorus. On the other hand, abundance of zooplankton negatively correlated with water temperature, transparency and water level. However, from the findings of this study suggested that the water quality parameters of the selected sites were found to be suitable for the survival of aquatic organism.

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Indian major carp, Cirrhinus cirrhosus was considered to monitor culture and health status in farm condition from Bhaluka and Muktagacha of Mymensingh region of Bangladesh for a period of seven months starting from September, 2010 to March, 2011. Monthly sampling was carried out for growth and health condition. Samples of skin and muscle, gill, liver and kidney were observed by clinical and histological techniques. Water temperature was at unfavorable levels but, dissolved oxygen, pH, alkalinity, ammonia and nitrite of water were within the favorable range for fish culture during the months of December and January. Clinically weak body, rough skin, scale loss, thick gill filaments, ulcer and gray brownish color were observed. Among the affected fish organs like skin, muscle and gill were found to be more affected than those of the internal organs, liver and kidney. Major pathologies in the skin and muscle were loss of epidermis and dermis, presence of fungal granuloma, fungal hyphae, necrosis, hemorrhages, vacuums and melanocytes. Protozoan cysts, clubbing, hemorrhages, necrosis and hypertrophy were found in the gill. Necrosis, hemorrhage, pyknosis and vacuums were observed in liver. Common pathological signs like necrosis, hemorrhage, pyknosis, vacuums and degenerated kidney tubules were noticed in kidney. Overall, in the clinical and histopathological studies fishes were found to be more affected during the colder months i.e., December and January. Whereas, in the month of February the pathological condition of fish gradually started to heal up. In histopathological observation, fishes of Bhaluka farms were more affected than that of Muktagacha fish farms. Epizootic ulcerative syndrome (EUS) and protozoan diseases were noticed in Bhaluka fish farms.

The present experiment was carried out in the household ponds (0.04 to 0.08 ha in area with 1.3 to 2.4 m in depth) of small indigenous people at Barind Tract region, northwest Bangladesh during September, 2017 to June, 2018 to know the growth performance of bivalve with carp. Two different treatments with 3 replicates were used, in treatment one (T1) only the carp polyculture was performed and in treatment two (T2) carp and bivalve polyculture was performed. Good quality of carp fingerlings (Labeo rohita, Gibelion catla, Cirrhinus cirrhousus, Hypophthalmichthys molitrix and Ctenopharyngodon idella) and freshwater bivalve (Lamellidens marginalis) seeds were stocked in the ponds. Stocking density and size of the seeds were similar for all of the study ponds. During the experiment there were no significant differences was observed in growth performance of the fishes between the two different treatments (p<0.05). The weight gain was recorded for L. rohita 420.31 g in T1 and 436.25 g in T2, for G. catla 237.01 g in T1 and 329.66 g in T2, for C. cirrhosus 263.53 g in T1 and 301.74 g in T2, for H. molitrix 559.6 g in T1 and 593.57 g in T2, for C. idella 510.11 g in T1 and 619.57g in T2. The weight gain of L. marginalis was 12.3 g in T2. During this experiment the production of carp was recorded 2524.5 kg/ha in T1 and 2618.2 kg/ha in T2 and the bivalve production was 1284.4 kg/ha in T2. This study is the first report on growth performance of bivalve with carp in the Barind Tract region of northwest Bangladesh. The result of this study will be helpful for the development of bivalve aquaculture in this climatically vulnerable region. J. Bio-Sci. 29(2): 99-110, 2021 (December)