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Abundance and Diversity of Zooplankton in Semi-intensive Shrimp (penaeus Monodon) Farm

Alokesh Kumar Ghosh
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Suman Kumar Saha
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Md. Rashedul Islam
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

S. M. Bazlur Rahaman
Fisheries and Marine Resource Technology Discipline, 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 shrimp farm of Bagerhat district from June 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. In the present study 5 groups of zooplankton were observed namely rotifer, copepod, cladocera, ostracoda and crustacean larvae. Among the various groups of zooplankton, the percentages of copepod, rotifer, cladocera, ostracoda and crustacean larvae in the culture system were 52%, 39%, 7%, 1% and 1% respectively. The zooplankton was dominated by copepods (52%) which showed more or less two peaks in August (833 individuals/L) and in October (815 individuals/L). Rotifer and copepod were about perennial while one genus Cypris of ostracod was found only in August. Three genus of copepod namely Diaptomus, Cyclops and Mesocyclops were identified in the study area of which Diaptomus and Mesocyclops were more or less dominant while four genus of which Brachionus and Filinia under rotifer and Daphnia and Diaphanosoma under cladocera were also found during the study period. The physico-chemical parameters and the zooplankton abundance showed some interrelationships. These relationships are helpful to understand the seasonal and spatial variation of zooplankton population. The findings of the present study would be helpful as baseline information for further plankton related research.

Keywords: Abundance, Diversity, Copepod, Shrimp

Location: Bagerhat district

Start Date: 00-00-2009

End Date: 00-00-2009

Program Area: Animal Health and Management

Commodity: Shrimp

Objectives:

To estimate the abundance and diversity of zooplankton in semi-intensive shrimp culture system and
To know if any relationship exists between zooplankton community and different water quality parameters.

Methodology:

Sampling station and sampling design: A semi-intensive Shrimp farm was selected for the present study which was situated beside the Bagerhat town in Bagerhat district and geographically located at 22^o36' to 22^o46' north latitude and 89^o40' to 89^o50' east longitude. The farm is on the Bhairab river. It is more or less rectangular in shape with a surface area of 4100 m² and a depth of 2.5 meter. The farm was joined with the river by a sluich gate so that coastal water could enter into the farm by a canal. 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. Sixty litters of pelagic water from 6 different parts of the farm were passed through the plankton net with the help of a plastic pan of 5 liter capacity. 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 analysis. 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.

Source of Information: International Journal of Life Sciences, 2011, : 5(1). 1-11

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

During the present study relevant Coefficient of correlation showed cladocerans had a significant relationship with water temperature (r =.304), pH (r =.490) and DO (r =.314). An inverse relationship was seen in case of transparency (r =.630), free CO₂ (r =.630), alkalinity (r =.630) and salinity (r =.630). It is found that cladocerans had no relationship with hardness. During field observation, the abundance of crustacean larvae was higher in the months of June, July and August while it was totally absent during the rest of the study period. Crustacean larvae showed positive correlation with temperature and free CO₂. During this study a comprehensive observation on the physico-chemical parameters and the zooplankton abundance and diversity has been made in a shrimp farm which was semi-intensive. The physico-chemical parameters and the zooplankton abundance showed some interrelationships. These relationships are helpful to understand the seasonal and spatial variation of zooplankton population. The plankton is considered to be the best index of the biological productivity and the nature of aquatic habitat. In semi intensive shrimp culture the growth of the individuals not only depends on the supplementary feed but also on the production of plankton. The physico-chemical parameters and the zooplankton abundance showed some interrelationships. These relationships are helpful to understand the seasonal and spatial variation of zooplankton population. So the presence of specific type of plankton is crucial for successful growth of shrimp and other aquatic organisms. From the present study it is found that the zooplankton abundance varies seasonally and it showed direct or indirect relationships with the physico-chemical parameters.

Knowledge Management: Journal