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Abundance and Diversity of Zooplankton in Semi Intensive Prawn (macrobrachium Rosenbergii) Farm

Jadobendro Shil
Fisheries and Marine Resource Technology Discipline, Life Science School, Khulna University, Khulna 9208, Bangladesh

Alokesh Kumar Ghosh
Fisheries and Marine Resource Technology Discipline, Life Science School, Khulna University, Khulna 9208, Bangladesh

S M Bazlur Rahaman
Fisheries and Marine Resource Technology Discipline, Life Science School, Khulna University, Khulna 9208, Bangladesh

Abstract/ Executive Summary:

The present study was carried out on the seasonal abundance and diversity of zooplankton in a semi- intensive prawn farm of Bagerhat district from July to December, 2008. Plankton samples were collected by conical shaped monofilament nylon net (Plankton net) and Lugol’s solution was used for preservation. The zooplankton abundance was influenced by physico-chemical factors. During the study period 11 genera of zooplankton under 5 orders were recorded from the study ponds namely Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae. Among all groups copepod was the dominant order. The percentages of Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae in semi-intensive culture system were 54%, 28%, 12%, 4% and 2% respectively. But the genera Brachionus under the order of Rotifer was dominant among all other genera. Cyclops and Helidiaptomus under the order of Copepod were the 2nd dominant genera. Numbers of zooplankton species were recorded to be the highest in summer season and minimum at early winter season. Highest number of zooplankton found at the month of October. Total zooplankton shows significant positive relationship with water temperature ((r = +0.384), Dissolve Oxygen(r = +0.113), pH(r = +0.320), Free CO₂ (r = +0.319), Alkalinity(r = +0.269), Hardness (r = +0.402) and negative relationship with Salinity(r = -0.486), Transparency(r = -0.693). The findings of the present study will help to improve the management strategies of shrimp culture system.

Keywords: Zooplankton, Diversity, Abundance, Copepod

Location: Bagerhat district

Start Date: 12-06-2008

End Date: 10-12-2008

Program Area: Animal Health and Management

Commodity: Plankton

Objectives:

To know about zooplankton abundance and water quality parameters in the semi-intensive prawn culture system.

Methodology:

Sampling station and sampling design: A semi-intensive prawn farm was selected for the present study which was situated beside the Bagerhat town in Bagerhat district and geographically located at 22°36′ to 22°46′ north latitude and 89°40′ to 89°50′ east longitude. The farm was on the Bhairab river of about 70 decimal and a depth 5-6 ft. The pond was joined with a canal so that fresh water could enter the pond. Two ponds were selected where semi-intensive culture was practiced. The samples were collected at 30 days interval from June 12th to December 10th, 2008. Three representative samples were collected to increase accuracy of the result. Plankton collection and preservation: Plankton samples were collected in monthly intervals at 10.30 am on each sampling date by conical shaped monofilament nylon net (Plankton net). The mesh size of the plankton net was 90 μm and the diameter of the net at mouth was 30 cm. Samples were collected from pelagic waters of the ponds from different parts of the ponds. The water was passed down through the net and the plankton condensed at the lower end of the plankton net then it was collected into a glass test tube and fixed firmly. After collection, the plankton materials were transferred into glass bottles and preserved with Lugol’s solution. About 250 ml samples of plankton were preserved with 1.5 ml Lugol’s solution. After preservation the plankton samples were carried out to the Biology laboratory of Fisheries and Marine Resource Technology Discipline for further analyses. Plankton identification: Plankton cells were enumerated under a light microscope by using Sedgwick-Rafter cell. Recognition of species is a matter of experience. Thus, a series of pencil and ink drawing on postcards of the species of the observed were prepared to identify the organisms. Identification was done. Counting: The quantitative enumeration of the zooplankton was carried out with the help of a Sedgwick-Rafter (S-R) counting cell which is 50 mm long, 20 mm wide and 1 mm deep. Before filling the S-R cell with sample, the cover glasses were diagonally placed across the cell and then samples were transferred with a large bore pipette so that no air bubbles in the cell covers were formed. The S-R cell was let stunned for at least 15 minutes to settle zooplankton. Then plankton on the bottom of the S-R cell was enumerated by compound microscope. By moving the mechanical stage, the entire bottom of the slide area was examined carefully. To achieve a random sampling, each time 3 fields were examined for each sample and an average of the counts had been recorded. The organisms thus counted, were expressed as cells per liter (cells) of the sample. From each sample 20 cells counts in 3 slides have been made to achieve random counts and an average of the counts has been recorded. Number of plankton (Zooplankton) in the S-R cell was derived. Measurement of physicochemical parameters: The physicochemical parameters such as temperature, transparency, pH, free carbon dioxide (CO₂), dissolve oxygen (DO), alkalinity, hardness and salinity were measured during the study period. Statistical analyses: Correlation and regression between various water quality parameters and abundance were done using Microsoft Excel Program and SPSS program.

Source of Information: Springer Plus 2013, 2:183 1-8

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

During the study period 11 genera of zooplankton under 5 orders were recorded from the study ponds namely Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae. Among all groups copepod was the dominant order. The percentages of Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae in semi-intensive culture system were 54%, 28%, 12%, 4% and 2% respectively. But the genera Brachionus under the order of Rotifer was dominant among all other genera. Cyclops and Helidiaptomus under the order of Copepod were the 2nd dominant genera. Numbers of zooplankton species were recorded to be the highest in summer season and minimum at early winter season. Highest number of zooplankton found at the month of October. Total zooplankton shows significant positive relationship with water temperature ((r = +0.384), Dissolve Oxygen(r = +0.113), pH(r = +0.320), Free CO₂ (r = +0.319), Alkalinity(r = +0.269), Hardness (r = +0.402) and negative relationship with Salinity(r = -0.486), Transparency(r = -0.693). The findings of the present study will help to improve the management strategies of shrimp culture system.

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