Releasing of giant freshwater prawn (Macrobrachium rosenbergii) for the purposes of stock enhancement and to create a fishery has been conducted in Thailand since the 1980s. In each year, over a hundred million post larvae (30 day old post larvae of ~1 cm) of M. rosenbergii have been released into inland waters nationwide. The stocking density is, generally, about 2,500 prawn larvae/ha. Average age at harvest is around 6 to 8 months, with an average total length of 20 cm. The individual weights can range between 100 and 200 g after a year of release.
Common fishing gears are gillnet, long-lines and traps, the latter designed exclusively for M. rosenbergii. Overall, the success of stocking M. rosenbergii is poor since the recapture rate is generally less than 5 %. However, the economic return is high. Average market price of M. rosenbergii is 150 Thai Baht/kg, which is about 3 times more than the average price of marketed freshwater fish. The profit is reported to be as high as 800 %. Moreover, the high market price of M. rosenbergii benefits traders at various levels, job creation and income for all related sectors. Although the economic profit is very high, the low rate of recapture of stocked M. rosenbergii makes this culture-based practice not entirely satisfactory. The major problem is that there are no guidelines in regard to the optimum size of seed for release as well as appropriate time and location to be stocked, that could enhance the rate of return and economic returns.
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