Browsing by Author "Ranathunga, R.M.N.P.K."

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    Comparative Study on Growth Performance and Profitability of Shrimp Farming Industry in Sri Lanka: Native Penaeus monodon vs. Imported Specific Pathogen Free
    (Uva Wellassa University of Sri Lanka, 2020) Priyadarshana, S.D.A.M.; Athula, J.A.; Ranathunga, R.M.N.P.K.; Lakmal, J.A.S.; Adikari, A.M.L.W.
    Until 2018, Penaeus monodon was the main commercial-scale cultured shrimp species in Sri Lanka and the seed production industry depended on wild-caught native broodstock. Due to the high prevalence of White Spot Disease among the wild-collected brood shrimps, the farming industry has been affected by post larvae shortage and disease outbreaks. As a solution, National Aquaculture Development Authority has decided in 2016 to introduce Specific Pathogen Free (SPF) broodstock to the industry imported from Thailand and they are planning to encourage the SPF shrimp farming in the country. Therefore, this study was focused to compare the growth performance and profitability of farming these two varieties. During the period of 21st March 2019 to 28th February 2020, 14 ponds for each variety were selected from the Ambakandawila area in Puttalam District for the study. Data collection was initiated after the 8th week of the stocking and continued up to the harvest. Specific Growth Rate (SGR), Survival Rate (SR), Average Daily Gain (ADG) of the body weight, Feed Conversion Ratio (FCR), total cost, revenue, and net profit were calculated. SGR was recorded as 2.51 ± 0.1 & 2.13 ± 0.06 and ADG of the body weight was recorded as 0.31 ± 0.02 & 0.23 ± 0.01 g day-1 for SPF and native shrimp varieties respectively. SR was recorded as 70.1 ± 3.4% & 69.9 ± 3.2% and FCR was recorded as 1.51 ± 0.04 and 1.54 ± 0.07 for SPF and native shrimp varieties respectively. It recorded 1,482,311.62 ± 50,687.49 and 1,087,716.21 ± 72,449.54 LKR acre-1 as the total cost of the farming of SPF and native shrimp varieties respectively. Total revenue was recorded as 1,783,733 ± 102,197 and 1,535,122 ± 162,199 LKR acre-1 and estimated net profit was calculated as 301,421 ± 105,412 and 447,406 ± 101,576 LKR acre-1 for SPF and native shrimp culture systems respectively. Although the SGR, SR, ADG, FCR are better in SPF shrimps than native shrimps, profitability mainly depends on the total cost. Keywords: SPF Penaeus monodon, Shrimp farming, Growth performance, Profitability
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    Effectiveness of Ultraviolet Filtration of Incoming Sea Water for Controlling Vibrio spp. in Shrimp Hatcheries in North Western Province
    (Uva Wellassa University of Sri Lanka, 2016) Pathirana, I.P.D.H.; Rajapakshe, R.M.G.N.; Jayamanne, S.C.; Ranathunga, R.M.N.P.K.
    Vibrio spp. are natural micro flora that presence in marine waters are one of the main factors which responsible for larval mortality of penaeid shrimp. To avoid bacteriological problems, shrimp hatcheries adopt extensive water treatments which include effective ultraviolet filtration. But there the effectiveness of UV filters is a considerable problem. Therefore effectiveness of UV filtration of incoming sea water for controlling the Vibrio spp. and the management procedures that can be implemented for improving the efficiency of UV filters were studied. Ten shrimp hatcheries out of forty seven hatcheries in north western province of the country were selected. Sea water samples were taken before and after the UV filtration and were subjected to the Total Vibrio Count (TVC) test. Thiosulfate Citrate Bile salt Sucrose (TCBS) agar was used as the culture medium and pH, salinity, Ammonium-N, Nitrate-N, Nitrite-N were checked. Questionnaire survey was also conducted for collecting information regarding water treatment systems, disinfection procedures and the factors affecting on the efficiency of UV filters. According to this study there is a significant difference by considering the TVC among hatcheries and between the TVC of sea water before and after UV filtering. It was observed that salinity and pH have no significant effect on the TVC. According to questionnaire survey, although each hatchery uses the UV bulb capacities which are relevant to the water flow rates by considering the water usage volume, the effectiveness of UV filtration is not in an efficient level when comparing the mean values of TVC of sea water before and after UV filtering. According to Chi square Goodness of fit test, availability of charcoal filters, maintaining the records of hours of UV filter operation, replacing UV bulbs after its life time and routine changing of filter media in sand, charcoal and cartridge filters have significant impact on the TVC of UV filtered water. Therefore productive maintaining of the filter system is very important for the effectiveness of UV filtration. Keywords: Water quality, Shrimp disease, Bacteriological problems, Water treatments, UV filters
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    Growth Performance of Black Tiger Shrimp (Penaeus inonodon) Based on Three Different Brood Stock Collecting Areas Handala, Beruwala and Mulathivu in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Ekanayake, E.M.H.Y.; Athula, J.A.; Atapaththu, A.M.D.N.S.; Ranathunga, R.M.N.P.K.
    Seed production of shrimp aquaculture industry in Sri Lanka is totally depends on the wild captured brood stocks. Among the 17 recorded brood stock collecting areas; Handala, Beruwala and Mulativu areas are provided proportionally higher amounts of brood shrimps to the industry. This study was carried out to investigate the differences of the growth performances of the cultured shrimps in accordance to the collecting area of the brood stock to produce post larvae (PL). 15 days old PL pertaining to three different collecting areas including three replicates for each area were stocked in fiberglass tanks (6m2) with the stocking density of 266m-2. Water quality, feeding and other management practices were maintained almost equally in all culture tanks. Initial PL quality, initial & subsequent average total length and average body weight were measured weekly up to the end of the culture period of 45 days. Survival rates, instantaneous mortality and specific growth rates were calculated. Data were analyzed using one-way ANOVA (P<0.05) to determine significant differences of growth parameters. It was revealed that no significant difference (P>0.05) of the initial body length and weight of PL stocks collected from three different areas. Though, initial quality parameters of the PL according to the brood stock collection area were not different significantly, lowest PL quality was recorded as 83% from Mulativu area and both Handala and Beruwala were recorded as 94%. After the culture period, highest significant (P<0.05) average body weight (1.04±0.08g), average body length (36.811.23min), highest significant instantaneous mortality rate (5.33±0.66) and lowest survival rate (51.0±9.53) were recorded for the PL produced using brood stock collected from Mulathivu area. There was no significant difference (P >0.05) of the specific growth rate of the all cultured shrimps. Overall results indicated that, there was no significant difference between the PL producing from brood stocks collected in three different areas.