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Development of Nursery Technology of Freshwater Prawn (macrobrachium Rosenbergii)

Md. Jahidul Hasan
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

Abstract/ Executive Summary:

The present study was conducted during June to December, 2010 with a view to developing a nursery technology with respect to stocking density optimization and survivability of prawn PL in earthen ponds. Hatchery obtained PL were reared with commercial nursery feed and monitoring of water quality for 14 weeks in 12 ponds (1.25dec each) at Khulna University. Four densities viz., 958, 500, 800 and 1000 PL/dec were used with three replicates in each. The range of temperature, DO, pH, alkalinity, hardness, ammonia and phosphate during the study were within the acceptable limit. The mean initial weight of prawn PL was 0.005g. Net gains in weight were 2.069, 4.042, 2.680, and 1.707g from the four treatments, respectively. The mean values of specific growth rate of the PL were 3.192, 3.550, 3.332 and 3.090% per day from the four densities, respectively. Highest values of growth rate and survival rate were found in 500 PL/dec density. Second highest values of the same were found in 800 PL/dec. However, a density of 500- 800 PL/dec may be used for better growth and survivability in the prawn nurseries, though there are scopes for further improvement of the process through feeding trial and/or other aspects.

Keywords: Macrobrachium rosenbergii, Nursery technology, Stocking density, Survivability

Location: Fisheries and Marine Resource Technology Discipline, Khulna University

Start Date: 00-07-2010

End Date: 00-11-2010

Program Area: Knowledge Management

Commodity: Prawn

Objectives:

This research endeavors to find out a technology for nursing prawn larvae with suitable feeding, fertilization and management of the nursery ponds by determining survival rate of the PL, optimizing stocking density of PL by appropriate feeding and developing technology for nursery management of prawn PL.

Methodology:

A total of twelve ponds, with adequate aquaculture facilities, located at the Khulna University premise, measuring 1.25 decimal each, were selected. With a view to develop a nursery technology of M. rosenbergii with respect to optimization of stocking density and survivability of PL in the nursery ponds the experiment was conducted during July-November of 2010.

The ponds were divided into three groups in accordance with the three treatments on density of stocking of the PL, each with three replications. Three densities were 500 PL/ decimal, 800/ dec. and 1000/dec. There was a control group of ponds with 958/dec density having the same number of replications. For convenience, the treatments were denoted as T1, T2, T3 and Tc. All ponds were enclosed with nylon netting of smaller mesh size with 0.6 meter height from its base for the protection from unwanted lives that might either be predator on the prawn PL directly or take a portion of feed applied for the PL, resulting poor growth and survival. To kill the insects and unwanted lives, the ponds were treated with Rotenone at the dose of 30 g/decimal for every 30 cm water depth. After one week, lime was applied into the ponds at a dose of 2 kg/dec. due to presence of excess black soil at the bottom of the ponds. After one week of liming, the ponds were fertilized with both organic (cowdung 10kg/dec) and inorganic (Urea and Triple Super Phosphate at 150g and 75g per dec., respectively) fertilizers. The PL were not stocked directly rather they were acclimatized for 4-5 hours keeping the poly bags submerged in the nursery ponds before stocking. Then they were stocked at the densities of 500, 800, and 1000 PL/dec. in the ponds marked as T1, T2 and T3 respectively and at 958 PL/dec. in the control group ponds. The PL was fed twice daily with a commercial larval feed for up to 4 weeks of stocking named “Yeon Feed”, and in the subsequent days, with a grower feed named “Quality Feed” at 10% of the body weight by using tray. Cow dung was applied at 1 kg/dec in every 15 days and Urea and TSP were applied once in every week at the rate of 50g/dec and 25g/dec respectively.

The stocking weight of the PL was recorded before releasing into the ponds. Data on growth of the PL in weight was recorded once in a week and the physico-chemical parameters of the pond water were also recorded fortnightly. A total of 20 PL from each pond was collected by using a push net (thela jal). For ease of weighing, the PL were anesthetized by a bath of 1 ppt Ethyl-4-amino benzoate (Benzocain) prepared at 10% alcohol (Shah, 1984). After measuring the individual weight of the PL in gram up to 3 digits after the decimal point by using an electric balance the sampled PL were returned to the respective ponds. Water temperature, dissolved oxygen (DO), pH, total ammonia, hardness, total alkalinity and phosphate were recorded fortnightly between 9.00 am to 11.30 am.

Source of Information: Khulna University Studies Volume 11 (1&2) and 12(1&2) : December 2013

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present experiment was carried out with a view to optimizing stocking density and survival rates in earthen nursery ponds in order to develop a nursery technology. Out of the four densities tried in Tc, T1, T2 and T3, the density 500PL/dec provided with the highest survival and net gain in weight; the second-highest survival and growth rate were achieved in the density 800PL/dec. Thus a density range of 500-800/dec may be recommended for use in the prawn nurseries for better growth and survivability.

Knowledge Management: Journal