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Duckweed (lemna Minor) as Supplementary Feed in Monoculture of Nile Tilapia, Oreochromis Niloticus

M. M. R. Chowdhury
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

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

M. S. Rahman
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

M. Sadiqul Islam
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

Abstract/ Executive Summary:

An experiment on duckweed (Lemna minor) as supplementary feed in the monoculture of nile tilapia (Oreochromis niloticus) was conducted for a period of 90 days. The experiment had two treatments each with three replications. In treatment-1 ponds were supplied with duckweed as supplementary fish feed and in treatment-2 ponds were kept as control (without supply of duckweed). Ponds were stocked at a stocking density of 80 fingerlings per decimal. The ponds were fertilized fortnightly with poultry dropping at the rate of 5 kg decimal^-1, urea 60 g decimal^-1 and TSP 90 g decimal^-1. Duckweed were supplied to the ponds (treatment-1) at the rate of 60% of the total body weight (wet weight basis) of the fish. During the experimental period, the ranges of physico- chemical parameters viz., water temperature, transparency, dissolved oxygen, pH, total alkalinity, free CO₂, PO₄-P and NO₃-N were within the productive limit and more or less similar in all the ponds under treatments 1 and 2. There were 27 genera of phytoplankton under five major groups and 11 genera of zooplankton under three major groups found in the experimental ponds. Mean survival rates in treatments 1 and 2 were 94.37 and 93.75%, respectively. Specific growth rate (SGR, % per day) of the fish in treatments 1 and 2 were 1.16 and 0.80%, respectively. Calculated net production of the fish in treatment-1 was 16.28 kg decimal^-1 year^-1 and in treatment-2 was 8.92 kg decimal^-1 year^-1. By t test it was found that the net production of fish in treatment-1 was significantly (p< 0.05) higher than that of treatment-2.

Keywords: Duckweed, Supplementary feed, Monoculture of Nile tilapia,

Location: Faculty of Fisheries Building, Bangladesh Agricultural University, Mymensingh.

Start Date: 00-07-2004

End Date: 00-10-2004

Program Area: Animal Health and Management

Commodity: Tilapia

Objectives:

To evaluate the efficacy of duckweed (Lemna minor) as a low cost supplementary feed in .the monoculture of Nile Tilapia

Methodology:

The experiment was conducted for a period of 90 days from July to October 2004 in the earthen ponds each measuring 40 m² (1 decimal) area at the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Before fish stocking water of the experimental ponds were drained out to eradicate all the undesirable fishes, renovated and liming was done in all the ponds at the rate of 1 kg decimal^-1. Ponds were filled up with DTW water and fertilized at the rate of poultry dropping 10 kg decimal^-1, urea 100 g decimal^-1 and TSP 100 g decimal^-1 as initial doses. The experiment had two treatments each with three replications. In treatment-1 ponds were supplied with duckweed as supplementary fish feed and in treatment-2 ponds were kept as control (without supply of duckweed). Ponds were stocked at a stocking density of 80 fingerlings of tilapia per decimal. The initial average length and weight of tilapia were 10 cm and 30 g, respectively. The ponds were fertilized fortnightly with poultry dropping at the rate of 5 kg decimal^-1, urea 60 g decimal^-1 and TSP 90 g decimal^-1. Duckweeds were supplied to the fish culture ponds (treatment-1) at the rate of 60% of the total body weight (wet weight basis) of the fish every day. Various physical, chemical and biological water quality parameters of ponds water such as water temperature (°C), transparency (cm), dissolved oxygen (mg L^-1), pH, free CO₂ (mg L^-1), total alkalinity (mg L^-1), PO₄-P (mg L^-1), NO₃-N (mg L^-1), phytoplankton density (cells L^-1) and zooplankton density (cells L^-1) were estimated fortnightly. Water temperature was recorded with a Celsius thermometer and transparency was measured with a secchi disc of 30 cm diameter. Dissolved oxygen was measured directly with a DO meter (Lutron, DO-5509) and a digital pH meter (CORNING pH meter 445) was used to measure pH. Free CO₂ and total alkalinity were determined by titrimetric method (APHA, 1981). PO₄-P (mg L^-1) and NO₃ N (mg L^-1) were determined by a Hach Kit (DR/2010, a direct reading Spectrophotometer). The counting of plankton (both phytoplankton and zooplankton) was done with the help of Sedgwick-Rafter Counting Cell (S-R cell) under a compound binocular microscope. The plankton population was determined. Identification of plankton (phytoplankton and zooplankton) up to generic level were made. Fish samples were collected with a cast net monthly to estimate the growth in length (cm) and in weight (g) and to check up the health condition of fish. At the end of the experiment, all fish were harvested through repeated netting by seine net. T-test of net fish production of the ponds under T₁ and T₂ was done by a computer using SPSS package programme.

Source of Information: Journal of Fisheries and Aquatic Science, 3(1): 54-59, 2008, ISSN 1816-4927.

Article Link (Online Journal): DOI: 10.3923/jfas.2008.54.59, URL: http://scialert.net/abstract/?doi=jfas.2008.54.59

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Higher production of Nile Tilapia fish in monoculture , attributed by the supplementary feeding of duckweed,Influence of duckweed on production of fish was found to be positively significant.

Knowledge Management: Journal