Improved extensive shrimp farming
Improved extensive shrimp farming is the most common production system among small-scale farmers in Vietnam. Especially farmers who lack access to finance or who are risk-averse continue to use this traditional shrimp farming method. Extensive shrimp farming is concentrated in Ca Mau, Bac Lieu, Kien Giang, Soc Trang, Ben Tre and Tra Vinh. The total farming area is estimated to be 337,000 ha.
|Average stocking density||
|# of crops per year||
No clear distinction between crops
|# of days per crop||
120 days or longer
All year round
|Type of farmer||
Type of farmers
Improved extensive shrimp cultivation is predominantly practiced by small-scale household farms. Farm sizes are typically around 3 to 5 hectares in size with ponds that can cover an entire farm. These smallholder farmers have limited access to finance and usually do not want to take a high risk by converting their farms from polyculture to a more intensive production system. In contradiction to mangrove-shrimp farming, these farmers receive less attention from NGO’s. As a result these farmers are less organised which leads to complex supply chains.
Production and harvesting system
Most of the farms practice polyculture with a few crabs. Water exchange is done using the tidal hub: at high tide, water is led into the pond, while the water is discharged at low tide. Approximately 40% of the pond water is exchanged every four days. During the production phase no aeration equipment is used.
Partial harvesting happens according to the new and full moon cycle. Though small volumes are harvested every day, main harvests are once in two weeks. The shrimp is trapped in bamboo boxes in the corners of the ponds and harvested according to size. Grow-out takes 120 days or longer depending on harvest size. Farmers harvest sizes ranging from 4/6 upto 50 HOSO/kg. Farmers tend to harvest larger sizes.
Target species and byproducts
The main target species in extensive systems is Penaeus monodon (black tiger shrimp), but due to natural water inlets other native shrimp species (pink and white shrimp) and fish species are also able to enter the pond. In some cases farmers also add crabs.
Stocking densities and productivity
Shrimp is partly stocked naturally during water intake. In addition, farmers stock hatchery PL throughout the year to increase productivity. Stocking densities of P. monodon range from 4 to 6 PL/m2. Annual production averages around 300-350 kg/ha.
If farmers stock crab as well, this would normally be around 500-1000 crabs per hectare. Farmers could harvest around 70-150 kg/ha/year.
Use of seed, feed and other inputs
As mentioned earlier farmers add hatchery P. mondon PL to the pond after water intake. There are many small and large scale hatcheries in Ca Mau but quality of PL varies widely. Sometimes PLs are first raised in a small nursery pond, or farmers stock bigger sized PL in their grow-out ponds.
Commercial feed is sometimes used, but is often based on experience rather than a feed plan. Farmers do not use chemicals, but some do use probiotics. Natural substances like tea seed cake is used to kill predators in order to prepare the pond for stocking.