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Optimisation of Stocking Density of Thai Silver Barb (barbodes Gonionotus Bleeker) in the Duckweed-fed Four Species Polyculture System

M.A. Wahab
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

M.E. Azim
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

A.A. Mahmud
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

A.H.M. Kohinoor
BFRI, Mymensingh

M.M. Haque
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

The optimisation of stocking density of Thai silver barb (Barbodes gonionotus) in the polyculture with Labeo rohita, Catla catla and Cyprinus carpio was investigated in seasonal ponds. Three different stocking densities of Thai silver barb i.e., 5,000, 6,000 and 7,000 fingerlings ha^-1 were tested with stocking density of carps fixed at the rate of 10,000 fingerlings ha^-1. Duckweed was applied to all ponds supplemented with rice bran and oil cake. There were no significant variations on either water quality parameters or abundance of planktonic organisms due to the different stocking densities of silver barb. A significantly higher fish production (p<0.05) was recorded in the ponds in which medium stocking density of Thai silver barb was maintained.

Keywords: Barbodes gonionotus, Stocking density, Polyculture, Duckweed

Location: Bangladesh Agricultural University.

Start Date: 00-07-1997

End Date: 00-10-1997

Program Area: Resource Development and Management

Commodity: Fish

Objectives:

To optimise the stocking density of Thai silver barb by comparing three stocking densities in the duckweed-fed carp polyculture system.

Methodology:

Experimental ponds and their preparation: The experiment was carried out for a period of 120 days between July and October '97 in six earthen fish ponds adjacent to the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Ponds were all equal in size and depth with pond area of 100m2 and average depth of 1.5 m. Ponds were initially cleaned and limed at the rate of 250 kg/ha. Then ponds got filled up with underground water. Before one week of fish stocking, ponds were fertilised with cattle dung, urea and TSP at the rate of 5,500, 125 and 100 kg /ha, respectively. Stocking of fish and pond management: The ponds were randomly divided into three treatment groups: ponds 1 and 4 in treatment 1 (T₁), ponds 2 and 6 in treatment 2 (T₂), and ponds 3 and 5 in treatment 3 (T₃). Fingerlings of fish of different species were collected from local supplier and stocked in the ponds. Rohu (Labeo rohita), catla (Catla catla), common carp (Cyprinus carpio) and Thai silver barb (Barbodes gonionotus) were stocked at the number of 33, 33, 34 and 50, respectively in each pond ofT 1; T₁ plus additional 10 fingerlings of Thai silver barb (T₂); T₂ plus additional10 fingerlings of Thai silver barb (T₃). Fish were fed at a rate of 3% body weight per day with rice bran and soaked mustard oil cake (2:1). Quantity of feed was adjusted fortnightly on the basis of sampled fish weights. Duckweed was supplied to the ponds in 1 m² floating bamboo enclosures and made available for 24 hours per day. Duckweed was established in a pond adjacent to the experimental site, harvested and added to the bamboo enclosures when needed. Ponds were fertilised fortnightly with cattle dung, urea and TSP at the rate of 5,500, 125 and 100 kg/ha, respectively. Limnological parameters: A series of physico-chemical parameters, viz., temperature, transparency, dissolved oxygen (DO), total hardness, pH, total ammonia, nitrate nitrogen (N0₃-N), phosphate phosphorus (P0₄-P) and chlorophyll-a of pond water were determined fortnightly between 0900 and 1000 hrs on each sampling day. Temperature, and DO were measured by a digital DO meter (YSI model 58). Transparency and pH of water were measured by a secchi disc and a pH meter (Jenway model 3020), respectively. Total hardness was determined by titrimetric method. Water samples were filtered for nutrient analysis except total ammonia which was determined on unfiltered sample. 'Nutrients were analysed by a Spectrophotometer. Quantitative and qualitative analyses of phytoplankton and zooplankton were made fortnightly. Sampling for plankton collection was performed after every one week of fertilisation. Samples were collected by passing 5 litre of water from three locations of each pond at different depths (surface, middle and bottom) through a plankton net. The concentrated plankton samples were preserved in small plastic bottles with 3% formalin. The number of plankton was estimated using a Sedgewick-Rafter counting cell (S-R cell). One ml concentrated sample was placed on to the counting chamber of the S-R cell (providing 1000 fields) and was left to stand for 15 minutes to allow the plankton to settle. Then the plankton on randomly selected 10 fields of the chamber were counted under a binocular microscope (Swift M-4000). Growth of fish: Fish samples were collected with a seine net fortnightly to estimate the growth in length (cm) and weight (g) for adjusting the quantity offeed application and to check up the health condition of fish. At the end of the experiment, all fish were harvested by dewatering the ponds.

Source of Information: Bangladesh J. Fish. Res., 5(1 ), 2001: 13-21

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The addition of duckweed and supplemental feed (rice bran and oil-cake) may compensate any inter-specific and intraspecific dietary competition and enhance the overall fish production within certain limits of stocking of Thai silver barb in the proposed four species polyculture system. The overall highest production was obtained from an additional stocking of Thai silver barb at the rate of 6,000 fingerlings ha^-1 rather than 5,000 fingerlings ha^-1 and 7,000 fingerlings ha^-1 with a stocking density of carps at 10,000 fingerlings ha·1 in the polyculture system.

Knowledge Management: Journal