| Abstract | This study was conducted in Thanh Binh and Cao Lanh districts of Dongthap province of Vietnam during January to April 2003, to assess the current status of river pen culture of giant freshwater prawn (Macrobrachium rosenbergii) in Southern Vietnam. The specific objectives of this study were to assess technical and socio-economic aspects of river pen culture of prawn, and to identify potentials, constraints and problems of river pen culture of prawn. Fifty-two pen farms were randomly selected for interviews among all pen farms in the study areas in the technical and socio-economic survey. Among these farms, twelve farms were randomly selected for field measurements of water quality and soil characteristics, with four pen farms from the upstream, middle stream and downstream, respectively. The survey showed that the prawn pen culture was developed and operated by farmers' indigenous knowledge. Men dominated in prawn pen culture and farmers' education background was very low. All the farmers used only family labor for pen culture activities. All the prawn pens were rectangle in shape, and built along rivers or canals bench in front of farmers' own house. Three sides of pens were made by bamboo, wood and fine nylon net, while the other side was the bench of rivers or canals. Most surveyed pens (86.5%) were smaller than 300 m2 , 9.6% between 300 and 600 m2 , and 3% larger than 600 m2 . Average size of pens was 209 m2 , ranging from 35 to 900 m2 . Prawns were monocultured in all pens, and stocked at densities of 9-278 PL/m2 with an average of 61.7 PL/m2 in June and harvested for 2-4 times starting from 4 months after stocking until late December or next January. Most (96.14%) prawn seeds were caught from the wild, while only 3.86% were hatchery-produced seeds. All interviewed farmers fed prawns with farmmade feed, which was prepared by locally available ingredients such as snails, mud crabs, trash fish, rice, coconut flesh and cassava roots. Average prawn yield was 522 kg/1,000 m2/year, ranging from 142 to 1,571 kg/1,000 m2/year. Average net return was US$711/1,000 m2/year, ranging from - US$1,244 to 4,366. About 73% farmers achieved positive net return, while about 27% farmers obtained negative net return. The top five constraints for the prawn pen culture were lack of culture technologies, poor water quality, disease outbreak, poor seed quality and lack of capital. All farmers had no environmental awareness, and the regulations for prawn pen culture have not been established. Field measurements showed that all measured water quality parameters were within the ranges for good growth of giant freshwater prawn, and indicated that there was no significant accumulation of nutrients and organic matter at the bottoms of rivers or canals. However, more research should be conducted to optimize stocking density of prawns in pens, to improve the feed preparation methods, and to assess the environmental impacts of prawn pen culture. |