Aminur Rahman M.
Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Amin S.M.N.
Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Ara R.
Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Arshad A.
Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Sperata aor, Fry, Stocking density, Fingerling, Growth, Production
Freshwater Station, Bangladesh Fisheries Research Institute, Mymensingh
Resource Development and Management
Broodstock collection and rearing- In total, 100 individuals of adult aor weighing from 700 to1250 g were collected from the Brahmaputra river-basin and floodplains of greater Mymensingh region during January-February, 2007. Immediately after collection, the fishes were transported to Freshwater Station, Bangladesh Fisheries Research Institute, Mymensingh and then reared in earthen ponds with supplementary feeds comprising rice bran (30%), mustard oilcake (29%), fish meal (40%), and vitamin-premix (1%) at the rate of 5-6% of the estimated biomass. The pond was fertilized at fortnightly intervals with cow dung (1,000 kg/ha) and Urea & TSP (50 kg/ha). Natural propagation- For stimulating natural propagation of aor, artificial holes (nests) were made on the pond bottom. Each hole was 0.7 m in diameter and 0.3 m in depth. A total of 30 holes were made in a pond having an area of 0.08 ha. Three months before the onset of the breeding season, 30 pairs of Aor breeders (700-1250 g) were stocked in the pond and fed with supplementary feed as stated above. Fresh groundwater was supplied every day to maintain natural phenomena for breeding. From mid-May to early-June 2007, a total of 19,428 Aor fry were collected from the holes by complete drying of the pond and then reared for 8 weeks in nursery ponds. Rearing of fry and fingerlings in nursery ponds- The collected fry of aor was reared for 8 weeks from 10 June to 5 August in nine earthen nursery ponds with a surface area of 0.012 ha and an average depth of 0.8 m each. To assess optimum growth and survival of fingerlings, different stocking densities of fry (No./ha) viz., 100,000 (T1), 150,000 (T2), and 200,000 (T3) were tested with three replicates for each. After dewatering, quicklime (CaCO, 250 kg/ha) was spread over the pond bottom. Ponds were then filled with groundwater and fertilized with organic manure (cowdung, 2500 kg/ha). Seven days after manure application, the pond water was sprayed with dipterex (2, 22-Trichloro-1-Hydroxy Ethyl Phosphate, manufactured by Ciba Ltd.) at the rate of 1.0 ppm to kill harmful insects and pathogens. Fry having an average length of 1.78± 0.28 cm and weight of 0.20±0.03 g was then stocked in the nursery ponds. Fry in all the experimental ponds was fed with commercial Saudi Bangla (SABINCO) fish feed viz., nursery (32.06% crude protein) for the first 14 days and starter-I (31.53% crude protein) from days 15 to 56. The rate of feeding was 14% of the estimated body weight of fry for the first two weeks, 12% for the second two weeks, 10% for the third two weeks, and 8% for the fourth two weeks. After stocking, the ponds were fertilized with cow dung (1000 kg/ha) at weekly intervals to hasten the primary productivity of the ponds. Physico-chemical parameters of pond water were monitored weekly between 09.00 and 10.00 h. Temperature (°C) and dissolved oxygen (mg/L) were determined directly by a digital water quality analyzer, pH by a digital pH-meter, and transparency (cm) by a Secchi disc, and ammonia nitrogen by a HACH water analysis kit. Total alkalinity was measured following the standard method. Quantitative and qualitative estimates of plankton in the nursery ponds were taken weekly. Ten liters of water collected from different locations and depths of each pond were filtered through a fine-meshed plankton net (25 µm) to obtain a 50 ml sample. The samples were preserved immediately with 5% buffered formalin in plastic bottles. A Sedgwick–Rafter (S–R) cell was used under a compound microscope for plankton counting. Plankton count was performed using the formula proposed by Rahman and Stirling. Each pond was sampled for thirty individuals each per week until fry attained the fingerling stage. Growth in terms of length and weight, specific growth rate (SGR), daily growth rate (DGR), and food conversion ratio (FCR) was estimated. SGR, DGR, and FCR were calculated according to Castell and Tiews, and De Silva and Anderson (1995), respectively. At the termination of the experiment, the fingerlings were harvested by repeated netting, followed by drying of the ponds. The live fingerlings were counted and weighed individually. Survival (%) and production (number/ha) of fingerlings were then estimated and compared among the treatments. Data analysis- The data on growth, survival, production, water quality parameters, and plankton abundance of different treatments were tested through one-way analysis of variance (ANOVA) using ‘Stat View’ version 4.0 followed by Duncan's New Multiple Range Test. The level for statistical significance was set at 0.05%. A simple cost-benefit analysis was implemented to estimate the net benefits from different treatments.
Iranian Journal of Fisheries Sciences; 14(1) 1-14; 2015
Journal