Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Comparison of Benthic Fauna of Two Beels Under Different Management System

M. Mukhlesur Rahman
Departrnent of Fisheries, Dhaka

Monoranjan Das
Department of Aquaculture, Bangladesh Agricultural University, Myrnensingh 2202, Bangladesh

Abstract/ Executive Summary:

A comparative study of benthic fauna between Rajdhala beel and Padmai beel of Netrakona District under different management system was carried out from July'99 to January'00. An average number of 1113 and 1175 organisms /m² were obtained from Rajdhala heel and Padmai beel respectively. A total of 22 taxa belonging to 8 diverse groups, Oligochaetes, Chironomids, Molluscs, Ceratopogonids, Diptera (other than Chironomids and Ceratopogonids), Ephemeroptera, Leeches and Crustaceans were recorded. Oligochaetes were dominated and constituted 46% and 49% of the total benthic population in Rajdhala beel and Padmai beel respectively. The next dominant group was the Chironomids, which constituted 31% and 30% of the total benthic population in Rajdhala beel and Padmai beel respectively. The highest number 1279 and 1437 individuals /m² of benthic fauna was recorded in December from Rajdhla beel and Padmai beel in respectively. The lowest number of benthic fauna 869 and 914 individuals/m² were found during September and July from Rajdhala beel and Padmai beel respectively. Monthly variation of benthic fauna among two heels were found statistically significant (p<0.05). The numerical distributions of benthic fauna was found to be varied with depth ranges. However, the depth wise variation of total benthic fauna between two heels was not found statistically significant. Fish yield of Rajdhala beel (488 kg/ha/yr) was appreciably higher than the Padmai beel (250 kg/ha/yr).

Keywords: Benthic fauna, Beel, Management system

Location: Netrakona District.

Start Date: 00-07-1999

End Date: 00-01-2000

Program Area: Conservation and Biodiversity

Commodity: Aquatic animal

Objectives:

To study the comparative abundance and depth distribution of benthic fauna of Rajdhala and Padmai beels.

Methodology:

Study area: The bees under study are located at Purbadhala thana of Netrakona district within 24°70' 25°8' N and 90°29' 90°48' E. Beels are in the Agro Ecological Zone (AEZ) 9 and subregion 9b of the country, which is under Old Brahmaputra flood plain. Rajdhala and Padmai beels is a semienclosed perennial round shaped water body.Rajdhala heel has a water depth 4.6-7.7 m and covers about 53 hectares water area. Whereas in Padmai heel water depth was recorded the maximum of 3m and the beel covers around 20 hectares. Rainfall is the main source of water in both the beel. During monsoon months the Rajdhala heel is connected by channel called Kumarkhali khal to the river Dhalai. There are two-outlet channels (khals), run away from the heel, which were fenced to prevent escape of fish, and Padmai beel is connected by a small channel to small river Kani. Watercolour appeared light green and brownish green in Rajdhala beel and Padmai beel respectively. The marginal slope and bottom of the Rajdhala beel was regular. Bottom was formed by clear clay mud. Thickness of the mud ranges from 50 to 80 cm. Physical nature of the bottom was soft and clear. The basin wall slope of the Padmai beel was lower than that of Rajdhala beel. Bottom mud was more soft and darker in colour. Unlike Rajdhala heel the bottom of Padmai heel was full of dead and decaying leaves of aquatic plants and rhizomes and tubers of emergent vegetation, which emitted a foul odour. Thickness of bottom mud ranges 70-120 cm. Sample collection: Benthic fauna of Rajdhala and Padmai heels were studied for a period of seven months from July'99 to J anuary'00. Benthic samples were collected monthly (15 or 16th day of the month) from each beel from 3 different depths say, shallow (0-1 m), medium deep (1-2m) and deep(> 2m). Three replicate samples were collected from each depth. For convenience, 9 sampling spot from each heel were marked with the help of bamboo poles to establish the sampling site. An Ekman-dredge covering an area of 225 cm² was used for sampling of bottom sediments using an anchored country boat. Content of the dredge, along with any materials caught were transferred to a bucket and taken to the shore for washing. Each sample was than washed thoroughly using a series of standard brass sieves of mesh size 0.2, 0.92 and 2.0 mm. From the residue the benthic organisms were collected under contrasting background of black and white by means of fine forceps and kept into separate vial containing 5% formaldehyde for preservation. The vials were marked properly and taken to the laboratory of Aquaculture Department of Bangladesh Agricultural University, for analysis. Physico-chemical data such as air temperature and water temperature, transparency (Secchidisc), pH oxygen, carbondioxide, ammonia hardness of water also collected on the sampling date by using Hach kit (DREL 2000). Sample analysis: After 48 hours the preserved animals were transferred to a petridish and washed with tape water to remove the remainder of the washable detritus and mud. Then benthic organisms were separated and counted into different major taxonomic groups by using a magnifying glass. The sorted animals were again preserved group wise into 5% formaldehyde and labeled properly for further study. On a later date the preserved specimens were identified into possible lower taxa under a dissecting microscope. The worms and larvae were soaked into lactophenol for a period of 24 hours for making them transparent for identification. The specimens were taken from lactophenol with the help of a fine forcep and were placed on a clean slide with a few drops of glycerine and covered with cover slip. A binocular microscope (NOVA 950 ES) with a magnification 16x4 were used to identify the specimens. The data obtained from the samples were tabulated for statistical analysis. Analysis of variance was done with the help of computer package MSTAT, following Randomized Block Design. The mean values was compared by Least Significant Difference Test at 5% level of significance.

Source of Information: Bangladesh J. Fish. Res., 5(2), 2001: 155-162

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The highest number 1279 and 1437 individuals /m² of benthic fauna was recorded in December from Rajdhla beel and Padmai beel in respectively. The lowest number of benthic fauna 869 and 914 individuals/m² were found during September and July from Rajdhala beel and Padmai beel respectively. Monthly variation of benthic fauna among two heels were found statistically significant (p<0.05). The numerical distributions of benthic fauna was found to be varied with depth ranges. However, the depth wise variation of total benthic fauna between two heels was not found statistically significant. Fish yield of Rajdhala beel (488 kg/ha/yr) was appreciably higher than the Padmai beel (250 kg/ha/yr).

Knowledge Management: Journal