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Study of Growth and Productions of Tilapia (oreochromis Niloticus) on Different Population Densities in Monoculture

F Sharmin
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202

MS Rahman
Professor
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202

M Shahjahan
Professor
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202

P Chowdhury
Scientific Officer
Bangladesh Fisheries Research Institute, Headquarters, Mymensingh-2201

Abstract/ Executive Summary:

The experiment was conducted to determine the effects of population densities of tilapia (Oreochromis niloticus) on the growth and production of tilapia in monoculture system. Fish population density was 80 fish per decimal under treatment-I, 160 fish per decimal under treatment-II and 320 fish per decimal under treatment-III. In the ponds under three treatments supplementary feed was not used. The average initial length and weight of the fry of tilapia was 4.48 cm and 0.067 g, respectively. The ponds were fertilized fortnightly with urea and TSP at the rates of 60 g, and 90 g per decimal, respectively. Mean survival rates of fish under treatment-I, treatment-II and treatment-III were 91.12%, 82.82% and 66.23%, respectively. The specific growth rates (SGR, % per day) of fish under treatment-I, treatment-II and treatment-III were 5.49%, 4.95% and 4.61%, respectively. The calculated net fish production of the ponds under treatment-I was 2.65 ton ha^-1 yr^-1 and that of the ponds under treatment-II was 2.55 ton ha^-1 yr^-1 and that of the ponds under treatment-III was 2.68 ton ha^-1 yr^-1. The net fish production under treatment-I and treatment-III were 2.65 ton ha^-1 yr^-1 and 2.68 ton ha^-1 yr^-1 higher than that of treatment-II, taking net fish production under treatment-I for 100%. According to survival rates and specific growth rates treatment-I is the best. So, the population density of 80 fish per decimal (under treatment-I) might be considered the best among the three treatments.

Keywords: Tilapia, Stocking Density, Production, Water Quality

Location:

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Tilapia

Objectives:

To find out the effects of three different population densities on the growth and production of tilapia (O. niloticus) in monoculture.

Methodology:

Six earthen ponds (40 m²) were used for the experiment. All the experimental ponds were arbitrarily numbered as pond no. 1 (P₁), pond no. 2 (P₂), pond no. 3 (P₃), pond no. 4 (P₄), pond no. 5 (P₅) and pond no. 6 (P₆) for the convenience of the research work. Ponds 1 and 5 were under treatment no. I, ponds 2 and 4 were under treatment no. II and ponds 3 and 6 were under treatment no. III. Before starting the experiment the ponds were dried, aquatic higher vegetation and unwanted aquatic animals were removed manually. Pond dykes were repaired and renovated. Liming (CaO) was done in all the ponds at rate of 1 kg decimal^-1 before 7 days of fertilization. Ponds were supplied with water after 7 days of liming from a deep tube-well water supply system; rainfall was also a source of water supply to the ponds. Fertilization of ponds was done weekly with the application of urea (60 g decimal^-1) and TSP (90 g decimal^-1). TSP was dissolved in water for 24 hours in a plastic bucket and then applied by spreading over the ponds surface by a mug. Urea was also dissolved in the same plastic bucket before spreading on the water surface of the ponds. Stocking of fish Fingerlings of monosex GIFT tilapia (O. niloticus) was stocked in the ponds. In treatment- I fish population density was 80 fish per decimal, 160 fish per decimal in treatment-II and 320 fish per decimal in treatment-III and fish were released after a week of fertilization. The initial average weight of O. niloticus was 0.067 g and initial average length of O. niloticus was 4.48 cm. Water depth (m): Depth of water of the experimental ponds was measured with the help of a graduated wooden depth meter. Transparency (cm): Water transparency of the experimental ponds was measured by a Secchidisk. Temperature (°C): Air and water temperature data were collected from ‘Weather Yard’ office of the Department of Irrigation and Water Management, BAU, Mymensingh. Dissolved oxygen (mg L^-1): Dissolved oxygen of water was measured by portable digital dissolved oxygen (DO) meter (model: DO5509, Lutron, made in Taiwan). pH (Hydrogen-ion concentration): pH was determined by a portable digital pH meter (Hanna Instruments, Italy, model-H 196107). Free carbon dioxide (mg L^-1): For determining free carbon dioxide of water, samples were collected in 250 ml black plastic bottles and titrated with 0.022 N sodium hydroxide solution using phenolphthalein as indicator . Total alkalinity (mg L^-1): To determine total alkalinity, samples were collected in 250 ml black plastic bottles and total alkalinity of water samples was determined by titrimentric method using methyl orange indicator. Phosphate-phosphours (PO₄-P) (mg L^-1): Phosphate-phosphorus (PO₄-P) of water samples of the ponds was determined by a digital Phosphate Meter (model HI 93717, Hanna Instruments). Nitrate-nitrogen (NO₃-N) (mg L^-1): Nitrate- nitrogen (NO₃-N) was determined by a digital Nitrate Meter (model HI 93728, Hanna Instruments). Methods for study of biological parameters Collection and preservation of plankton samples: Water samples in a 500 ml bottle were randomly collected for quantitative and qualitative study of phytoplankton and zooplankton of water from different locations of each of the ponds and passed through a plankton net (mesh-size 55 μ) and finally concentrated to 100 ml. Then concentrated samples were preserved in small plastic bottles in 5% formalin for study under a compound microscope. Counting of plankton: Counting of both phytoplankton and zooplankton were done with the help of Sedgwick-Rafter Counting Cell (S-R cell). Calculation of plankton: The plankton population was determined by Sedgwick Rafter counting Cell (S-R Cell) using the following formula (Rahman, 1992). N = A × 1000 × C / V × F × L; Where, N = No. of plankton cells per liter of original water, A = Total no. of plankton counted, C = Volume of final concentrate of the sample in ml, V = Volume of a field = 1 mm³, F = No. of the fields counted, L = Volume of original water in liter. The number of phytoplankton and zooplankton were expressed as cells L^-1. At the end of the experiment all the fish of the ponds were harvested by a fish net. Estimation of survival rate, growth and production of fish (i) The survival rate was estimated by the following formula: Survival rate (%) = No.of harvested fishes / Initial no.of fishes × 100 (ii) Specific growth rate (SGR %) was estimated by the following formula: SGR (% per day) = loge W₂ - loge W₁/ T₂ – T₁× 100; Where, W₁= Initial live body weight (g) at time T₁, W₂= Final live body weight (g) at time T₂ (iii) Calculation of gross fish production (ton ha^-1 yr^-1) = Gross weight (kg) of fish per decimal per month ×250 ×12 1000 (iv) Calculation of net fish production (ton ha^-1 yr^{- 1}) =Net weight (kg) of fish per decimal per month ×250 ×12/1000; T-test of net fish production of the ponds under three treatments was done by a computer using SPSS package programme.

Source of Information: Int. J. Agril. Res. Innov. Tech. 9(2): 76-83, December 2019

Article Link (Online Journal): DOI: https://doi.org/10.3329/ijarit.v9i2.45414

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present results were higher production from higher stocking densities compared to that achieved with the lower densities. Gross and net production 8.87 and 7.33 ton ha^-1 yr-1; 7.12 and 5.58 ton ha^-1 yr^-1; 4.69 and 3.16 ton ha^-1 yr^-1 under treatment-I, treatment-II, and treatment-III, respectively, which are more than those of the present experiment. It is apparent that the population density of 80 fish per decimal is the best for monoculture of monosex GIFT tilapia (O. niloticus). In treatment-III benefit was negative i.e. there was loss (23%) because of higher fish population density (320 fish per decimal). So excessive higher fish population density do not give profit rather there may be loss.

Knowledge Management: Journal