MS Islam
Professor, Department of Coastal and Marine Fisheries, Sylhet Agricultural University, Sylhet, Bangladesh
A Hossain
Research Associate, Fisheries Component, KGF Project, Sylhet Agricultural University, Sylhet, Bangladesh
Socioeconomic characteristics, production cost, Return, Factors, problems
It is situated by the side of Sylhet-Sunamganj high way and close to Sunamganj district town.
Variety and Species
The study was performed in the Dekar haor one of the most important and largest haor of Bangladesh. Dekar haor lies between latitude 24°46´N to 24°57´N and longitude 91°20´E to 91°31´E. It is situated by the side of SylhetSunamganj high way and closes to Sunamganj district town. The study was conducted for a period of four months from July 1 to October 29, 2018. Twelve nylon net cages (1.5 × 3 × 3 m) were used as a culture system. The frame of the cage was made of a bamboo split. Plastic drums were used as cage float. Net cages were made of plastic or knot-less polyethylene net (mesh 1.0 cm). Cages were hanged with a cage frame. A bamboo-made platform was set up over the cages and all cages were fixed with the poles of the platform. Cages were installed at both sides of the platform for easy feed supply and intensive observation. The open part of each cage was covered with another piece of the net (mesh 7.0-7.5 cm) to avoid escaping fish and predation by bird. This study was one factorial in which probiotics were the only experimental variable as T1 (Safegut), T2 (Biogen), T3 (Super biotic) and T4 (control) each with three replicates. The place selected for setting the cages was cleaned manually and the selected place was limed with agricultural lime (CaCO3) at a rate of 250 kg ha-1. After six days of liming, all cages were stocked with the required quantity of fry of male tilapia (O. niloticus) at a density of 40 no. m-3 with the average initial weight of 14.23-16.44 g. Monosex tilapia fry was purchased from Pirojpur private fish hatchery, Sylhet Sadar, Sylhet and was transported in oxygenated polythene bags from hatchery to experimental area. Before stocking, fry was acclimatized to the cage water for one and half hour period. Initial weight and length of 10% of fishes were recorded before stocking in cages. Stocked fry of tilapia was fed with commercial mega floating feed at a decreasing rate of 10-5% of body weight thrice daily until the previous day of harvest. Proximate compositions as moisture, crude protein, crude lipid, ash, crude fiber, carbohydrate of supplemented feed were respectively 11, 30, 7, 15, 8 and 29%. Probiotics namely Safegut, Biogen and Super biotic were mixed with commercial feed at a rate of 0.5 g kg-1 of feed following the instruction of the manufacturer to assess their role on growth and yield of monosex tilapia. The total daily feed ratio was divided into three equal portions and was applied in the morning between 8.00-9.00 am, at noon 12.00-1.00 pm and in the evening 5.00-6.00 pm. The feeding amount was adjusted every 15-day intervals depending on the bodyweight of stocked tilapia. Net of the cages was cleaned and checked every 7-day intervals. The behavior of tilapia was regularly observed especially after providing feed in the morning and in the evening to determine their conditions as movement, feeding intensity, body colour and diseases. Water quality parameters like surface temperature, transparency, dissolved oxygen (DO) concentration, pH, total alkalinity and ammonia were determined at fortnightly intervals between 9.00-10.00 am at the time of fingerlings sampling. Surface water temperature was measured on the spot 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). Ammonia nitrogen was measured using ammonia test kit (Biosol, A.A. Biotech PVT LTD., Fishtech BD Ltd). Fortnightly sampling was done to determine the growth of tilapia fry and to adjust the feed rations. Growth was measured regarding weight (g) with digital balance and length by measuring scale. Tilapia were totally harvested after 120 days of culture. They were caught using a hand scoop net and lifting all cages from the water on the same day. After harvest, all tilapia of cages were counted and weighed individually to determine growth, survival rate and yield. Specific growth rates (SGR), food conversion ratio (FCR) 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 (%) = (Number of fish harvested ÷ total number of fish stocked) × 100 SGR (% /day) = {Ln (final body weight) – Ln (initial body weight) × 100}/cultured period. 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 fish) Economic analyses of tilapia cage farming under different treatments was calculated on the basis of purchasing prices of tilapia fry, feed, fertilizers, lime, transport cost, cage materials and revenue from the sale of harvested tilapia. At the end of the study, all fish were sold at the local market. Tilapia was sold at a rate of Tk. 120.00 kg-1. Net profit and cost-benefit ratio (BCR) were calculated using the following formula: Net profit = Total return – total cost and BCR = Total return ÷ total cost Survival rate, growth and yield variables were analyzed using one-way analysis of variance (ANOVA) to compare the treatments means. If the main effect showed significance, the ANOVA was followed by Duncan’s Multiple Range Test. All ANOVA were tested at a 5% level of significance using SPSS (Statistical Package for Social Science) version 20.
J. Sylhet Agril. Univ. 5(2):195-202, 2018
Journal