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Effects of Stocking Density on Production and Economics of All-male Tilapia (oreochromis Niloticus) Culture in a Rain Fed Rice-fish Ecosystem

M. A. R. MRIDHA
Department of Fisheries, University of Rajshahi, Rajshahi, Bangladesh

M. NAHIDUZZAMAN
WorldFish, Cereal Systems Initiative for South Asia, Rangpur, Bangladesh

M. S. UDDIN
Bay of Bengal Program Inter-Governmental Organization, Chennai, India

A. K. M. AZAD SHAH
School of Agriculture and Rural Development, Bangladesh Open University, Gazipur, Bangladesh

M. A. HOSSAIN
Department of Fisheries, University of Rajshahi, Rajshahi, Bangladesh

Abstract/ Executive Summary:

Effects of stocking density on the growth, production, and economics of all-male tilapia (Oreochromis niloticus) were investigated in a rain-fed rice-fish ecosystem for a period of 120 days. Fish were stocked at the rate of 4000, 5000, and 6000 ha⁻¹ in treatments T₁, T₂, and T₃ , respectively. Water quality was suitable for fish culture. Significantly higher growth was observed in T₁ as compared to other treatments. SGR ranged from 1.26 to 1.51. Survival varied between 79% and 88% with treatment T₁ producing the highest survival. The highest benefit:cost ratio was obtained in T₂ followed by T₁ and T₃. The best fish production (457.21 kg ha⁻¹) and economic return for the culture period was obtained at 5000 fish ha⁻¹.

Keywords: Stocking density, All male tilapia, Rain fed ecosystem, Total biomass, Economic returns

Location: Kushtia Sadar Upazila, Kushtia district, Bangladesh.

Start Date: 00-08-2010

End Date: 00-11-2010

Program Area: Farming System

Commodity: Tilapia

Objectives:

1. To evaluate the production economics of a rice-fish system under different stocking densities of all male tilapia.

Methodology:

This study was carried out in nine rice plots of varying sizes (0.05–0.1 ha) at Kushtia Sadar Upazila, Kushtia district, Bangladesh, for a period of four months during August–November, 2010. Rice plots were assigned randomly to three treatments each with three replications. About 10–12 cm of rice straw and roots were left during harvesting of the previous rice crop. After harvesting, plots were left for 1 month until the next rice cropping season started. During this period, embankments (1.5 m height and 1.0 m width) and ditches (1.0 m depth representing 5% of the total paddy area) were constructed. These ditches were constructed at the lower part of the fields to provide refuge to fish during high water temperature and low water depth. The ditches were prepared by frequent ploughing, followed by application of lime (CaCO₃) at the rate of 125 kg ha⁻¹, cattle dung at 500 kg ha⁻¹, and urea and triple super phosphate (TSP) at the rate of 25 kg ha⁻¹ after 7 days of water filling. The plots were ploughed three times with a power tiller and then leveled properly with a ladder before transplanting the rice seedlings. Stubble from the previous crop was incorporated into the soil. Weeds were removed manually from the fields before transplantation of rice seedlings. Rice seedlings (BR-11 variety) were transplanted from a nursery into the experimental plots 35 days after seeding. Rice seedlings were transplanted at an alternate spacing of 15 and 35 cm between the rows and 20 cm within the rows, with 2–3 seedlings per hill (Bangladesh Rice Research Institute 2010). The alternate rice spacing has the advantage of allowing more light to penetrate the water surface and enhancing aquatic photosynthesis. Rice seedlings were allowed to establish at a shallow water level of less than 5 cm before the stocking of fish. Triple super phosphate, muriate of potash and gypsum were applied at the rate of 52, 82, and 60 kg ha⁻¹, respectively, and mixed with the soil during the time of last ploughing (Bangladesh Rice Research Institute 2010). All of these plots were also fertilized with a total of 150 kg ha−1 of urea at 15, 30, and 45 days after transplantation (DAT) (Bangladesh Rice Research Institute 2010) as top-dressing in three equal splits. All male tilapia fingerlings were purchased from a private nursery and stocked at the rate of 4000, 5000, and 6000 ha⁻¹ in three treatments: T1, T2, and T3, respectively, at 15 DAT. Fish fingerlings were batch-weighed and released into the ditch. The average stocking weight of the fish at stocking was 18.2 ± 0.17 g. No feed or extra fertilizers were applied to the fish during the study period. Approximately 10% of the fish were sampled fortnightly, weighed, and measured to assess their health and calculate growth rates. Water quality was monitored fortnightly between 10:00–11:00 h. Water temperature was recorded with a thermometer. Water transparency was recorded with a Secchi disc; pH, DO, ammonia-nitrogen and alkalinity were measured using a HACH kit (model FF-2). Soil sediment pH, organic matter, available phosphorus, and available nitrogen were measured at the beginning of the experiment and immediately after final harvest. Organic matter was determined by the wet oxidation method; total nitrogen was determined by the Kjeldahl method (P Selecta Pronitro-T); phosphorus was determined by the Modified Olsen method (Hitachi, UV2800). Rice yield was determined after harvest and converted into ha⁻¹. Fish were harvested by repeated netting and draining of the rice plots. At harvest, 10% of the fish were randomly sub-sampled, individually weighed, and measured. Growth performance of fish was calculated. Benefit-cost analysis was performed on the basis of the prices of fertilizer, fish seed (including transport), and the revenue from the sale of fish. At the end of the study, all fish were sold in a local market. The prices of inputs and fish correspond to the market prices in Bangladesh in 2010 and were expressed in USD (1 USD = 80 BDT during the experimental period). Data on both fixed and variable costs were recorded to determine the total cost (USD ha⁻¹). Total return determined from the market price of rice, straw and fish was expressed as USD ha−1. The net return and benefit cost ratio (BCR) were calculated.

Source of Information: Journal of Applied Aquaculture, 26:60–70, 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Tilapia culture in rice field is technically feasible and economically viable. The higher survival, relatively faster growth, low variation in weight, and higher production rate of all male tilapia stocked at 5000 ha⁻¹ showed that the culture in rain fed rice fish ecosystem could be a possible alternative to ponds for the commercial production of tilapia.

Knowledge Management: Journal