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Macrobenthic Fauna of Kaptai Lake (bangladesh)

K. K AHMED
Scientific Officer
Riverine Sub-station, Fisheries Research Institute, Rangamati 4500, Bangladesh

G C HALDAR
Principal Scientific Officer
Riverine Station, Fisheries Research Institute, Chandpur, Bangladesh

M M HOSSAIN
Research Officer
Ministry of Youth and Sports, Bangladesh Secretarial, Dhaka, Bangladesh

S K PAUL
Senior Scientific Officer
Third Fisheries Project, Fisheries Research Institute, Santhaher, Bangladesh.

Abstract/ Executive Summary:

Functional role of benthic communities in the trophic dynamics of reservoir ecosystems is well known. The Kaptai lake (lat. 22° 20- 23° 18' N, long. 92° 00'-92° 26' E) was the result of the construction of a dam across the river Kamafuli at Kaptai in 1961. Occupying an average area of 58 300 ha with a water reserve of 524.7 x 10⁷ m³ , it is the biggest man-made lake in South-East Asia (Fernando 1980). Although made primarily for hydroelectric power generation, it is used for freshwater fish production, navigation, irrigation and flood control also. The maximum and mean depth of the lake arc 32 m and 9 m, respectively, with a mean annual water level fluctuation of 8.14 m (Aquatic Research Group 1986).

Keywords: Macrobenthic fauna, Kaptai lake, Aquatic animal, Fish

Location: Rangamati zone, Bangladesh

Start Date: 00-07-1988

End Date: 00-12-1988

Program Area: Animal Health and Management

Commodity: Aquatic animal

Objectives:

To determine the Macrobenthic fauna of Kaptai lake (Bangladesh)

Methodology:

Samples were collected fortnightly during July-December 1988 from 5 stations of predetermined depth at Rangamati zone. At each sampling station, 3 samples of the lakebottom sediments were seived through a series of standard scives (38 |im to 500 urn mesh size). Samples were fixed in 5% formalin solution. Identifications were done group-wise after Pennak (1953), Needham and Needham (1966) and Ward and Whipple (1959). Data were analysed through completely randomized design (CRD). Duncan's multiple range test (DMRT) was conducted and correlation coefficient was determined wherever necessary. Chironomid larvae, oligochaetes and pelecypods were the dominant groups and were available in all the stations at dfferent depths. The dominance of these groups of macrobenthos has been reported by Dewan (1973), Mandal and Moitra (1975), Gupta (1976) and AH etal. (1978) from tropical freshwater fish ponds and reservoirs and by Puke (1949) and Moore (1980) from certain temperate waters. The dominance of these groups may be due to suitable ecological condition such as high level of organic matter in the bottom soil of the lake (Fisheries Research Institute 1990). The abundance of total benthic macrofauna varied from 99 ind./m² (September) to 163 ind./m2 (December). There was a progressive increase of total population from September till December. This agrees with the findings of Moitra and Bhowmick (1968), Patnaik (1971) and Raman. Chironomid larvae was the dominant group constituting 44.6% of the total bcnthic population. The peak abundance of chironomid was observed in October (77 ind./ m² ) and the trough in December (31 ind./m² ). However, monthly chironomid count did not show any significant difference («= = 0.05). Oligochactes constituting 36.62% of the total bcnthic fauna were the second dominant group. The density of the oligochactes declined from July till October but increased thereafter suddenly till December. Significant increase in the difference (« » 0.05) in abundance of oligochaetes was observed in December (83 ind./m² ).

Source of Information: Indian Journal of Fisheries 38(3):173-176, September 1991

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Depth-wise distribution showed the greatest numbers of bottom organisms at a depth of 11-13 m and the lowest at 7-9 m. Chironomids showed no depth preference but oligochaetes preferred a depth of 11-13 m. A poor occurrence of culicids was found at all depth ranges. The maximum percentage of pclccypods was at the highest depth range (15-17 m) and that of gastropods at the lowest depth range (7-9 m). No gastropod was available at higher depth ranges (13-17 m). Gupta (1976) found that the molluscs were abundant in the shallow depth of the Loni reservoir. Abundance of molluscs in the shallow depths can be attributed to the presence of weeds as they offer both food and shelter. Patnaik (1971) reported that the distribution of gastropod in the outer channel of Chilka lake was scant and irregular probably because of lack of sheltered areas such as vegetation, pebbles and stones. A narrow fluctuation in the distribution of benthic organisms in different depth ranges was attributed to the distrubance of their habitat. Edaphic and endemic factors like periodical lowering of water level and rain water incursion might have affected the ecology of die lake; Food also plays an important role in the distribution of benthic organisms (Ball 1948) and the nature of the bottom has a selective influence on the quality of the fauna (Welch 1952).

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