Md. Akhtar Hossain
Department of Fisheries, University of Rajshahi, Rajshai-6205, Bangladesh
Md. Anwar Hossain
Department of Fisheries, University of Rajshahi, Rajshai-6205, Bangladesh
Md. Ayenuddin Haque
Department of Fisheries, University of Rajshahi, Rajshai-6205, Bangladesh
Md. Mostafizur Rahman Mondol
Department of Fisheries, University of Rajshahi, Rajshai-6205, Bangladesh
Md. Harun-Ur-Rashid
Department of Fisheries, University of Rajshahi, Rajshai-6205, Bangladesh
Carp, Drought prone area, Fattening, Pond water quality, Species combination
Tanore upazila under Rajshahi district, Bangladesh
Animal Health and Management
Location and duration of study- The present experiment was conduction for a period of 6 months from July to December, 2018 in ponds (Mean area, depth and age of 0.64±0.07 ha, 1.99±0.05 m and 10.56±1.29 years, respectively) of Tanore upazila under Rajshahi district, Bangladesh. Experimental ponds were well exposed to sunlight and facilitated through inlets and outlets for water drainage. Embankments of the ponds were high enough to protect the run off. A randomized completely block design (RCBD) was followed for carrying out the present experiment with three different treatments of carp species combinations like T1: surface feeder- 30%, column feeder-40%, and bottom feeder-30%; T2: surface feeder-40%, column feeder-30% and bottom feeder-30%; and T3: surface feeder-35%, column feeder-35% and bottom feeder- 30%. Each treatment had three replications. Two surface feeders namely catla, Gibelion catla and silver carp, Hypophthalmich- thys molitrix; one column feeder namely rohu, Labeo rohita; and two bottom feeders namely mrigal, Cirrhinus cirrhosus and carpio Cyprinus carpio var. specularis were used in the present experiment. Stocking densities of the carps (2470 fishes/ha) were same for all the treatments. Stocking size of the fishes were 413.11±1.39, 410.56±1.84, 406.00±5.20, 340.55±4.02 and 248.78±1.35 g for G. catla, H. molitrix, L. rohita, C. cirrhosus and C. carpio var. specularis, respectively. Experimental ponds were subjected to removal of aquatic weeds manually. Predatory and unwanted fishes were removed through repeated netting. Ground water was used for all the ponds to maintain the water depth of around 2.0 m throughout the culture period. Both wild (Indian major carps) and hatchery (exotic carps) seeds reared through overwintering were used for stocking into the ponds under different treatments. Considering the soil and water quality of barind area of Bangladesh, low alkalinity and high turbidity mitigation strategy for the ponds was followed through lime treatment (Basal dose 750 kg/ha and periodic dose 60 kg/ha/fortnight) after Hossain (2011). Guideline for GAP aspects was followed after DoF (2012) and no organic manure was used except limited use of inorganic fertilizers (urea @ 120 kg/ ha/month and triple super phosphate, TSP @ 635 kg/ha/month) to enhance the natural feed and regular use of supplementary feed to increase the fish growth. Fishes were fed with commercial feed (25% protein content) twice daily at average 5% of body weight 6% for 4 months and 3% for rest of the study period. Water quality parameters of the experimental ponds were monitored between 09:00 am and 10:00 am in each month. Water temperature was recorded with the help of a Celsius thermometer at 20-30 cm below the water surface. Water transparency (cm) was measured by a Secchi disk. Alkalinity (mg/l) and ammonia-nitrogen (mg/l) were determined by the help of a HACH kit. Dissolved oxygen (mg/l), pH and total dissolved solids (TDS) were determined by a Multimeter. Plankton was identified using the key after Ward and Whipple (1959), Prescott (1962) and Bellinger (1992) and their concentration in water was determined by the help of a microscope after Stirling (1985). For heavy metal analysis, water samples from all studied ponds were collected at a depth of about 0.3 m below water surface into 500 ml plastic bottles. Prior to sampling, the bottles were cleaned with 10% nitric acid and rinsed with distilled water. The bottles were rinsed three times with the pond water at the time of sampling. Immediately after sample collection, 2 ml nitric acid was added to the water samples to reduce adsorption of metals onto the walls of the plastic bottles. Sample bottles were then labeled to indicate date of sampling and the sampling pond. Samples were transported in an ice-box to the laboratory and stored at 4°C awaiting analysis. Samples were digested through concentrated HNO3 and hydrogen peroxide acid (5 ml) and the determination of cadmium (Cd) and lead (Pb) concentrations were carried out by the use of Flame Atomic Absorption Spectrometer (Shimadzu, AA-6800) in central lab of University of Rajshahi, Rajshshi. For the bacteriological analysis, 500 ml of water samples were sampled from each studied ponds. The sample was labeled and stored in the dark to prevent the entry of light and photolysis. The sample was delivered to the laboratory of Department of Fisheries, University of Rajshahi, Bangladesh as quickly as possible i.e. the time gap between sampling and analysis was maintained below 3 h. In the laboratory, total heterotrophic bacterial (THB) count was done in plate count agar and Pseudomonas and Aeromonas in GSP Agar (Pseudomonas Aeromonas Selective Agar Base), Salmonella and Shigella in SS Agar plate (Hi Media). Two steps were followed to analyze Escherichia coli in pond water samples. Firstly, total and fecal coliform were detected in MacConkey Agar plate and secondly, the colony of bacterial cells appeared as green metallic sheen in MacConkey Agar plate were tested for E. coli after the confirmation with biochemical test (iMVIC test). Colony counts were made from plates with a digital colony counter and expressed as colony forming units (cfu/ml) of the sample. Cost-benefit analysis of different treatments was calculated on the basis of the cost of lime, ash, fertilizer, fish seed and labor used; and the income from the sale of fishes. The prices are expressed in Bangladesh currency (BDT; 80 BDT = 1 USD). The following simple equation was used according to Asaduzzaman et al. (2010) to find out net return: R = I-(FC + VC + Ii) Where, R = net return, I = income from fish sale, FC = fixed/ common costs, VC = variable costs and Ii = interest on inputs The benefit-cost ratio was determined as: Cost-benefit ratio (CBR) = Net benefit/Total input cost. Environmental parameters; fish growth and yield; and economics of carp fattening under different treatments were analyzed by one-way analysis of variance (ANOVA). When a mean effect was significant, the ANOVA was followed by Duncan New Multiple Range Test (Duncan, 1995) at 5% level of significance.
Archives of Agriculture and Environmental Science 5(2): 114-122 (2020)
Journal