Umashing Marma
Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet, Bangladesh
M S Islam*
Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet, Bangladesh
M Biswas
Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet, Bangladesh
P Das
Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet, Bangladesh
P R Das
Department of Aquaculture, Sylhet Agricultural University, Sylhet, Bangladesh
Cage farming, Stocking density, Growth performance, Survival rate, Production.
Dekar haor, Sunamganj district.
Animal Health and Management
Study area and duration The study was carried out in the Dekar haor (naturally depressed seasonal-perennial open waterbody), one of the most important and largest haor of Bangladesh. The haor is bounded by four upazilas (Dakshin Sunamganj, Sunamganjsadar, Dowarabazar and Chhatak) of Sunamganj district. It is situated by the side of Sylhet-Sunamganj high way and closed to Sunamganj district town. The study was conducted for a period of 4 months from 20 August to16 December 2016. Cage preparation and setting Nine newly constructed floating nylon net cages (3 m × 3 m × 1.5 m) were set in the periphery of the haor. Frames of cages were made by GI pipes and aluminium drums (250 L) were used to float the cages in water. Wet cages were made of knotless polyethylene net (mesh 1.0 cm). Cages were hanged with cage frame. Bamboo made platform was set up over the cages and all cages were fixed with poles of the platform. Cages were installed at both sides of the platform for easily feed supply and intensive supervision. Open part of each cage was covered with another piece of nylon net (mesh 7 to 7.5 cm) to avoid escaping of fish and predation by bird. Stocking density The study was a one factorial in which three stocking densities like T1 (35 no. m-3 ), T2 (40 no. m-3 ) and T3 (45 no. m3 ) were used. Each treatment of the experiment had three replicates. The place selected for setting the cages was cleaned manually and limed with CaO at a rate of 250 kg ha-1 . After 5 days of liming, all cages were stocked with required quantity of fry of all male tilapia (O. niloticus). Monosex tilapia fry were purchased from a private hatchery and was transported in oxygenated polythene bags from hatchery to experimental site. Before stocking, fry were carefully acclimatized to the cage water for one hour period. Initial average weight and length of 30 fishes were measured and kept into record before stocking in cages. Feeding Commercial Mega floating feed was used for feeding purposes. Feeding was started at 10% of body weight of fish initially and gradually decreased up to 5% until the end of the study. Total feed for a day was divided into three equal and was applied in the morning between 8.00-9.00 am, in noon12.00-1.00 pm and in evening 5.00-6.00 pm. Feeding rates were adjusted every 15 day intervals depending on the body weight of stocked tilapia. Net of the cages were cleaned and checked every 15 day intervals. Behavior of tilapia was regularly observed especially after providing feed in the morning and in the evening to determine their conditions such as movement, infection, colorations and diseases. Stocked fry of tilapia were fed with commercial feed Mega at a decreasing rate of 10-5% of body weight thrice daily until the previous day of harvesting. Proximate compositions as moisture, crude protein, crude lipid, ash, crude fiber, carbohydrate of supplemented feed were 11, 30, 7, 15, 8 and 29 %, respectively. Sampling of fish Fortnightly sampling was done to determine the growth of tilapia fry and to adjust the feed rations. Growth was measured in respect of weight (g) with digital balance (CAMRY digital electrical balance Model EK 3052, Bangladesh) and length by measuring scale. Sampling was continued until harvesting. Water quality measurement Water quality parameters of water as surface temperature, transparency, dissolved oxygen (DO) concentration, pH, total alkalinity and ammonia were determined at fortnightly intervals between 9 and 10 am at the time of fingerlings sampling. Surface water temperature was measured in situ using a standard centigrade thermometer. Transparency was recorded using Secchi disc. Dissolved oxygen was determined using a portable DO meter (YSI digital DO meter, Model 58, HANNA Company, America). pH of cage water was recorded using pH meter (HANNA Company, America). Total alkalinity was measured by titrimetric method (APHA, 2000). Nitrate and ammonia were measured using ammonia test kit (Biosol, A.A. Biotech PVT LTD., Fishtech BD LTD). Observed parameters Tilapia were harvested after 120 days of culture. They were caught using hand scoop and lifting all cages from water on the same day. After harvesting, all tilapia of cages were counted and weighed individually to determine survival rate, growth and yield. Specific growth rates (SGR), food conversion ratio (FCR), protein efficiency ratio (PER) and survival rate (%) were calculated following the equation as cited by Pechsiri and Yakupitiyage (2005). The equations are as follows: Weight gain: Mean final weight-Mean initial weight Survival rate (%): (Total number of harvested fish/ Total stocked fish) ×100 SGR (% day-1): {Ln (final body weight)-Ln (initial body weight) x 100}/cultured period (day). Protein efficiency ratio (PER): Weight gain (g)/protein consumed (g) Feed conversion ratio (FCR): Feed consumed (g dry weight)/Live weight gain (g wet weight) of fish. Yield of fish: No. of fish caught × (average final weight of fish-average initial weight of fish). Economic analysis of the different treatments was calculated on the basis of purchasing prices of tilapia fry, feed, fertilizer, lime, transport cost and the revenue from the sale of tilapia. At the end of the study, all fish were sold at local market. Tilapia were sold at a rate of Tk. 120.0 kg-1 . The analysis was performed based on market prices in Bangladesh for fish and all other items expressed in Bangladeshi taka (Tk.). The net profit and cost benefit ratio (BCR) were calculated using the following formula: Net profit: Total return – total cost BCR: Total return/total cost Statistical analysis Survival rate, growth and yield variables were analyzed using one way analysis of variance (ANOVA) to compare the treatments means. If the main effect was found significant, the ANOVA was followed by Duncan’s Multiple Range Test (DMRT). All ANOVA were tested at 5% level of significance using SPSS (Statistical Package for Social Science) version 20.0.
J. Sylhet Agril. Univ. 4(1):121-128, 2017 ISSN: 2308-1597
Journal