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Rice-prawn and rice-shrimp culture in coastal areas of Viet Nam

by Le Thanh Hung

Tidal flats in coastal areas are flooded periodically during high tides. During the dry season, salinity is usually higher than 5 ppt (per thousand); thus, most paddy fields are in fallow. In the rainy months, salinity declines so rice cultivation is possible. Farmers in these coastal areas of southern Viet Nam have living standards lower than their counterparts in freshwater regions. Integrating freshwater prawn culture with rice during the rainy season, as well as marine shrimp monoculture in the dry season, is one way of increasing their incomes. Both systems are described here.

Site selection

Dike and trench construction


Note: If stocking density is higher than 1/mē, supplementary feeding should be done and trench-to-ricefield rate should be higher than 10 percent. If water exchange is poor, do not stock higher than 1/mē.


50 percent - rice bran, broken rice or rice grain
20-30 percent - cassava root or broken maize
20-30 percent - trash fish, shrimp or prawn head wastes or oil cake

Predator prevention

Predators include sea bass, tilapia, snakehead and other wild fish that compete with the prawn for feeds. Predation can result in very low prawn yields.

Before stocking prawn, use any of the following measures:

Within the culture time, put gill nets in the trenches to catch the predators going to the ricefields.

Care and maintenance


Note: Transfer small prawn immediately to a hapa (net cage) to keep them alive for the next culture. Bring harvested prawn as soon as possible to the dealer or keep them in ice so that they stay fresh.

Land preparation and transplanting for rice


Pest control

Note: In case the above measures cannot control pests, pesticide application can be an alternative. Before applying the pesticide, drain water in the field to let prawn take refuge in the trench for 3-5 days.

Monoculture of prawn or shrimp in fields during dry season

Stocking density - 1/mē
Stocked juveniles - 2 g/head
Feeding rate - 2-3 percent of body weight
Feed formula - 50 percent rice bran (broken rice), 50 percent trash fish (fiddler crab, oil cake)
Culture time - 5-6 months
Other procedures are similar to freshwater prawn culture.

Estimated cost and return (in VN$) of rice-prawn culture in 1 ha coastal areas in South Viet Nam

Issues for further consideration

The situation described here is that before 1992 when the major shrimp disease outbreak in Asia occurred. Since then, disease in shrimp farming has become a major risk that has totally altered the economics of the system and has to be considered according to local prevalence. It is a major constraint to farmers, even for very extensive operations. Existing and ongoing epidemiological studies by Stirling University is applying epidemiological approaches to understand risk factors for farmers in these systems.

Resource constraints to these systems should be given attention. All the feeds given represent an investment in time or cash and this should be considered. Collection of snails and fish is a major activity that is not typically shared equally by all household members.

There are large areas of semi-saline zones around Asia (e.g. Bangladesh and India) and elsewhere, and this case study should be of relevance there. These tend to be marginal areas where poorer people live.

In other contexts, after shrimp production became established, outside interests have become influential and extract much of the value from shrimp culture. In Viet Nam, government policy prioritizes increased rice production areas. Large areas are being protected from saline intrusion, and converted to triple rice crop production, from previous shrimp culture, although in the transition, farmers are trying to grow shrimp as long as possible (e.g. grown at salinities less than 4 g/litres) due to much higher returns.

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