An economic anylysis was made to determine the cost of fish production in the floodplains at Daudkandi Upazilla in Comilla district during the period form January to April, 2007. Survey method was followed to collect data from 20 floodplain aquaculture projects. The projects record books and personal interviews of the NGOs and Fisheries officers were the main instruments of data collection. Statistical tools such as: range, mean, standard deviation and percentage were employed for analysis of data. The Cobb-Douglas production function model was used to estimate the values of co-efficients and related statistics of production function of fish culture in floodplains. Out of eleven explanatory variables, seven co-efficients had positive sign while only four co-efficients showed negative sign. The co-efficients bearing positive sign i.e., embankment construction, nursery and land lease, fertilizer and lime, fingerlings, feed, labor and staff wages and miscellaneous cost made positive impact on the farm income, while the co-efficients having negative sign i.e., area of floodplain, Office management, compensation and harvesting and marketing cost decreased the farm income. Summation of the production co-efficients i.e., return to scale (∑bi) was found 1.023 which implies that per one taka investment in floodplain fish culture will give rise to a profit of Tk. 1.02. The value of R 2 was found 0.892, which means that the variations in farm income could be explained to the extent of 89.2% by the included variables. The remaining 10.8% variations could not be accounted for by the multiple regression analysis. Average fish production in the selected floodplains was 2920.43 kg/ha of which production of cultured fish and indigenous fish was 2697.35 and 223.08 kg/ha respectively. The cost of fish production, total return and net income were estimated Tk. 1,153,08.55, 1,76,385.49 and 61,076.94 /ha. respectively. Benefit cost ratio was found 1.53.

An experiment on induced breeding of Bheda/Meni fish (Nandus nandus) was carried out to determine the optimum dose of pituitary gland hormone during December 2018 to June 2019 at Floodplain Sub-station of Bangladesh Fisheries Research Institute (BFRI), Santahar, Bogura. In this experiment, PG was used as inducing agent for both male and female fish. For induced breeding, PG was administered at the rate of 1, 2 and 3 mg/kg body weight to male brood fish, and correspondingly 2, 4 and 6 mg/kg body weight to female brood fish that were considered as the treatments namely, T1, T2 and T3, respectively. Fifty pairs of male and female fish were collected from the Raktadaha beel from where forty-five pairs were selected for induced breeding and the average body weight of the male and female were 43.0±2.5 gm and 55.2±3.0 gm in T1, 45.1±2.9 gm and 56.0±2.8 gm in T2, and 40.3±2.4 gm and 52.6±3.2 gm in T3. The male-female ratio was maintained as 1:1 in the breeding hapa. It was observed that female and male brood fishes ejected eggs and milt, respectively at the contemporary times. Ovulation occurs naturally after 8-10 hours of injection. The fecundity of fish (body weight 45 to 60 gram each) varied from 7,232-27,546. The fertilized eggs were hatched within 16-20 hours. The hatchlings were reared in rearing tank up to 5 days. The fertilization rate of Nandus nandus were 76±4 %, 93±5 % and 57±3 %, in T1, T2, and T3, respectively and the hatching rate were 72±3 %, 86±2 % and 61±4 % in T1,T2 and T3, respectively. Both the fertilization and hatching rates were significantly higher (p<0.05) in T2 treatment than T1 treatment followed by T3 treatment. The mean values of water temperature (°C) were 29.5±1.15, 30.0±2.03 and 30.8±1.76°C, pH was 7.4 ±0.46, 7.8±0.53 and 7.3±0.49 and dissolved oxygen (mg/L) were 5.5±0.61, 5.3±0.24 and 5.8±0.56 in brooder tanks, breeding hapa and larval hapa, respectively during the experiment and did not vary (P>0.05) among them and were suitable for induced spawning of Nandus nandus. Based on the findings of the present experiment, it was revealed that T2 showed the best outcome in terms of fertilization rate (93±5%) and hatching rate (86±2%) among the three treatments under optimum water quality parameters where PG hormone were used at the rate of 2 and 4 mg/kg body weight for male and female fish, respectively. Therefore, the present findings could be used in induced breeding of N. nandus for the development of hatchery propagation. Further trials on rearing or culture of this endangered fish under different stocking densities or feedings might be conducted at on-station and on-farm levels in Bangladesh as well as elsewhere of this region to save the fish from extinction or for its conservation and rehabilitation.

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.

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A checklist of the native fishes of the Roktodaho beel of Adamdighi and Raninagar Upazila under the Bogura and Naogaon districts of Bangladesh, where data were collected monthly by field survey, focus group discussions, and personal interviews by using a semi-structured questionnaire and a pictorial check list of fish species from a professional fishing boat caught by different nets, traps, and hooks from July 2021 to June 2022. A total of 36 species under 8 orders belonging to 19 families were recorded, of which 29%, 28%, 25%, and 8% were available, seasonal, rare, and very rare, respectively. Among those, 8 fish species (22.22%) were in the threatened category (1 critically endangered, 2 endangered, and 5 vulnerable), according to the IUCN Bangladesh. Notably, the globally threatened Channa orientalis and Wallago attu were available in the study area. According to their place of residence, 24 (66.67%) of the fish were floodplain residents except Glossogobius giuris, which is a mixed residence (reverine, estuarine, and floodplain) species. This residence status of fish indicates that the species have chosen their ideal environment. Dewatering, katha fishing, and the use of unlicensed technology were the main dangers. Creating and maintaining fish sanctuaries, reducing human effects, passing fishing regulations, and increasing consciousness may all help to preserve the current supply of fish. Strategies for restoration must be performed in the Roktodaho beel to preserve the fish range.