| Summary: | <p>Aquaculture is the fastest food growing activity in the world food sector. The global aquaculture production increased 13 times, from 8.53 million tonnes in 1970 to 64.82 million tonnes in 2007. Total annual global production of all freshwater prawn species was nearly 460,000 tonnes with a value exceeding US $ 1.8 billion in 2007. Main freshwater prawn species commercially cultured in the world is Macrobrachium rosenbergii, Experiments were conducted at Brackish Water Prawn Breeding Station Pambala, Chilaw. First experiment was conducted to determine the suitable male and female ratio for <em>Machrobrachium rosenbergii</em> under Sri Lankan hatchery conditions. In this experiment males and females in 1:10, 1:8, and 1:5, 1:3 ratios were cultured under artificial conditions in the hatchery. Three cement tanks (8x6x1m) each separated into 4 parts by using plastic mesh frames were used. Each replicate had one blue clawed male and the experiment was repeated. Results revealed that 1:5 ratio gave significantly higher (P<0.05) larvae, while in 1:10 ratio both eggs and larvae were in minimum numbers. The second experiment was conducted to determine the optimum salinity level for spawning of gravid females under Sri Lankan conditions. For this experiment, four fiber glass tanks each of 1000 L having two gravid females were used. Salinity was kept at 4, 5, 6, and 7 ppt and a constant temperature of 28<sup>0</sup>C was maintained. Experiment was repeated three times. Results revealed that 5 ppt salinity gave the optimum conditions. These results could be used to obtain higher production of <em>M. rosenbergii</em> seeds under Sri Lankan conditions.</p><p><strong>Key Words: </strong>Macrobrachium rosenbergii; Male: female ratio; Salinity level.</p><p>DOI: http://dx.doi.org/10.4038/tar.v22i4.3793</p><p><em>TAR </em>2011; 22(4): 410-415</p>
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