Browsing by Author "Nisansala, R.A.C."

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    A Geographic Information System (GIS) approach in identification of the potential reservoirs for Giant Freshwater prawn (Macrobrachium rosenbergii) culture: A case study in Moneragala district, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2015) Nisansala, R.A.C.; Rathnayake, R.M.C.W.M.
    Culture Based Fishery (CBF) is a better approach to overcome poverty and malnutrition in Moneragala District since the district is enriched with large number of village reservoirs and minor perennial reservoirs. Introducing a valuable, high demanding and protein rich species such as Giant Fresh Water Prawn (Macrobrachium rosenbergii) through CBF is the best way to get the maximum utilization of these natural resources. Current practice of stock enhancement of Macrobrachium rosenbergii in reservoirs has resulted a heavy loss of stock and low returns. Therefore it needs a careful selection of potential reservoirs prior to stocking of post larvae. As a tool in decision making, Geographic Information System (GIS) is still a new concept for CBF in Sri Lanka for aquaculture planning. The main intent of this study was to highlight the role of GIS in identifying potential reservoirs for stock enhancement of Macrobrachium rosenbergii under inland CBF in Moneragala District, Sri Lanka by developing a map. Methodology Nineteen minor perennial reservoirs distributed over nine divisional secretariat divisions in Moneragala District were visited during the dry season as the sample. Climate (Rainfall, Temperature), Bio-physical (Elevation) and Water quality (pH, Temperature, Hardness, Alkalinity, Dissolved Oxygen, transparency) and Socio-economic factors (proximity to roads and village, land use, poverty and population) were identified as influential factors for Macrobrachium rosenbergii culture based fishery. Data were collected from field surveys and responsible government institutes. Water quality parameters were tested on site and the university laboratory. In order to generate thematic layers for above each factors Interpolation techniques were applied for climate, elevation and water quality data; Population and poverty were considered in respective to DS divisions; multiple ring buffers were created for the proximity factors. Each factor was classified according to four suitability scales; very suitable, suitable, moderately suitable and unsuitable. Land use types in the district land use map were classified according to their suitability. Factors were ranked according to their relative influence on Macrobrachium rosenbergii fishery and weights were assigned according to their relative influence using the method of “Rank Sum”. Finally, all thematic layers were integrated in ArcGIS 10.1 (Esri, 2012) environment to generate the potential map. Results According to the resulted map (Figure 1) unsuitable areas occupy about half of the extent of the district. If potential reservoirs for Macrobrachium rosenbergii culture were indicated in respective to DS divisions, Badalkumbura, Moneragala, Wellawaya, Medagama and Sevanagala divisions were resulted as highest potential areas. Thanamalwila, Bibile, Madulla, Buttalaand Siyambalanduwa divisions were resulted as Suitable areas and Latter part of Madulla was indicated as Moderately suitable area.The district can gain more benefits by stocking M. rosenbergii in reservoirs that fall in most suitable areas.Since the water quality parameters were given the highest weight final result has high influence by water quality factor. Results are basically applicable to the dry season which is the period that water quality data were collected. According to the field observations dry season is not favorable for CBF. Application of CBF at present is not in a satisfactory level with compared to the existing number of reservoirs.Potential areas resulting from multi-criteria evaluation (MCE) are mostly associated around the reservoirs where the optimum water quality for M. rosenbergii culture exists. Results could be advanced by tallying the obtained results with catch data of Giant Prawn as some reservoirs are already practicing prawn culture, but lacking of accurate catch data was a limitation for the research.