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White Spot Syndrome Virus Vulnerability of Tiger Shrimp (penaeus Monodon) Cultured in the Coastal Ponds of Cox’s Bazar Region, Bangladesh

Mohammad M. Monwar
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Mohammad Z. R. Chowdhury
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Nani G. Das
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Mohammed S. Alam
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Mohammad E. Hoque
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Mohammad R. Islam
Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.

Abstract/ Executive Summary:

Jumbo tiger prawn, Penaeus monodon is the world’s most popular cultivable species for its fast growth, hardy nature, delicious taste and market demand. During the last three decades shrimp culture has been expanded rapidly. White spot Syndrome Virus (WSSV) is a great treat to this culture expansion. In this research, WSSV free fries were stocked in four coastal ponds with different salinities. The stocking density was kept low and constant. Water parameters, fish growth, and WSSV contamination were recorded fortnightly. The WSSV contamination was primarily detected by using Enbio Shrimp Virus Detection Test Kit, ‘Shrimple’ and further confirmed by the PCR test. Among the ponds, Pond A, B, and C were in completely controlled environmental condition where as pond D was traditional one that exposed to tidal variations. Physico-chemical parameter varied from as, temperature 29 to 32ºC, salinity 0 to 31‰, water pH 7.1 to 8.3, dissolved oxygen 3.8 to 6.3 mL L^-1, alkalinity 80-122 mg L^-1, ammonia 0 to 1.5 mg L^-1 and transparency 23 to 50 cm. The WSSV was found positive in the pond D just after hundred days, when the average weight of the shrimps was 26.69 g. It is observed that rapid change in the salinity and temperature, poor environmental conditions and uncontrolled exchange of water made the shrimp more vulnerable to the WSSV.

Keywords: White Spot Syndrome Virus, Shrimp disease, Tiger shrimp, PCR test

Location: Cox’s Bazar, Bangladesh

Start Date: 00-00-2012

End Date: 00-00-2012

Program Area: Pest Management

Commodity: Virus

Objectives:

To report the white Spot Syndrome Virus vulnerability of Tiger shrimp (Penaeus monodon) cultured in the coastal ponds

Methodology:

Studies were carried out at Samridhi Multipurpose Aquaculture Facility and Research Center (SMAFRC), located in the southeastern part of Bangladesh in the district of Cox’s Bazar. Bordered on the south – west by the Bay of Bengal, the district of Cox’s Bazar constitutes about 29,131 ha devoted to shrimp culture. There are many private and government owned brackish water aquaculture project around the north-west side of the city. The climate of the area is similar to that of other areas bordering the Bay with certain regional variations. The temperature in this region varies from 18 to 35 ºC; the humidity remains high (70%- 90%) almost through the year. Average annual rainfall varies in between 350 cm to 500 cm. The salinity of the water of Bankkhali River ranges from 0 to 32‰. The soil of the area is silt–clayey mixed with sandy loam having good water retention capacity. The pH value of the area varies from slightly acidic to slightly alkaline. The tidal amplitude along the coast is quite high. The land elevation of the farm site from the mean lower low water level (MLLW) is about 2 meter while the tidal amplitudes during spring tides are 3.0 to 3.3 m, voicing suitability for the construction of tide fed ponds. The present studies on the vulnerability of WSSV on P. monodon at different water environments through some modification in low density/existing culture systems was carried out in 4 earthen ponds at Cox’s Bazar, Bangladesh. The areas of the ponds A, B, C and D were 1240 m², 128 m², 135 m², and 560 m² respectively. Pond A and D were saline with water exchange by tidal fluctuation from Bankkhali River. The inlet of pond A was fitted over nylon screens (mesh size 350 micron) to prevent the entry of pest species and escapes of shrimps, where as the pond D was fitted over bamboo pens with nylon net (mesh size 0.5 cm) to prevent the entry of big size fishes. Pond B was moderate saline water with water exchange by pumping and pond C was completely fresh water with no water exchange. Pond A, B and C have controlled environmental conditions where as pond D has uncontrolled or traditional pond environments. Ponds were dried and renovated with respect to dykes, depth, slope, bottom elevation, supply and drainage facilities. Soil pH was assessed prior to application of treatments. These ponds were limed (agricultural lime, CaCO₃) at a rate of 800-1,200 kg ha^-1. Then inorganic fertilizer was applied (100-200kg ha^-1; Urea:TSP 2:1) followed by organic fertilizer (cow dung, containing 50% moisture) at a rate of 4-5 ton ha^-1. Ponds were filled with water up to 1.2 meter. After 3-5 days when the color of the water turned green, WSSV free PL (confirmed by PCR Test) were purchased from the local hatchery and stocked at a rate of 3 pl m-2 early in the morning. In case of pond B and C no water exchange was done. Only new water was added with same quality if pond water level was reduced due to evaporation. In pond A, about 40- 50% of water was exchanged daily during spring tides of full and new moon and the water level was maintained between 1.0 and 1.2 m. In case of pond D, water was exchanged naturally and uncontrolled with tidal fluctuation in spring tides times, but a blockage was used to retain water after the last spring tide. Through out the culture period no supplementary feed was given. To maintain sufficient natural feeds, subsequent to each water exchange inorganic fertilizers were applied at a reduced rate (Urea 35 kg ha-1 and T.S.P. 20 kg ha^-1). Sometimes organic manure was also provided at a rate of 2 ton ha^-1. Major water quality parameters like water temperature, water pH, salinity, dissolved oxygen, alkalinity, ammonia, and Secchi depth were recorded fortnightly with great care and accuracy. Growth was observed fortnightly by random sampling of 50 indivs/pond. After removing the water by means of bloating paper, the shrimp were weighted individually by an electronic balance. Body length was measured with the help of a fine-headed divider and millimeter scale. Shrimps were collected fortnightly for WSSV test. Initially En-Bio Shrimp Virus Detection Kit “Shrimple” was used to detect WSSV. WSSV positive results were further confirmed by PCR test. The PCR examination was carried out by the Center for Health and Population Research of International Center for Diarrhoeal Disease Research, Bangladesh (ICCDR’B).

Source of Information: AACL Bioflux, 2013, Volume 6, Issue 4. 320-332.

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Achievement/Findings:

Rapid change in the salinity and temperature, poor environmental conditions and uncontrolled exchange of water made the shrimp more vulnerable to the WSSV.

Knowledge Management: Journal