Salt intrusion has led to disturbances that directly impact some major farming species in Mekong Delta, Vietnam. Almost nothing can grow in affected areas. Rice, brackish water shrimp (tiger prawn) and pangasius are most effected victims. It is suggested that the farmers in affected areas should adapt and take advantage of the changes of environment. Aquaculture is affected, and it’s also aquaculture that is a solution for it. Some provinces in the country have come up with a plan, starting with a transformation from raising brackish water species to salt water species.
High salinity (> 25‰) areas is the right environment for some seawater species that have high economic value such as: seabass, garrupa, flathead grey mullet, snubnose pompano. These are high value fishes that have great potential for export and are favored in many Asian countries such as China, Japan, Malaysia, Thailand, and Singapore.
Seabass can adapt to captive environment in Mekong Delta. The proper density, suggested by experts, is 1.5 fish per square meter. Seabass’s FCR can be 1.5. Harvest size is 1 kg/fish after 9 months of stocking. Productivity can reach 8 tonnes per hectare. Seabass can be raised in pond or cage, using commercial feed.
Garrupa has become more popular to the coastal province of Kien Giang in Mekong Delta. After one year of stocking, Garrupa can reach 1 – 1.5 kg and can be harvested. The proper density should be 1 – 1.5 fish per square meter. Productivity 5 – 7 tonnes per hectare. Vietnam has recently managed to supply breeding stock of Garrupa to farmers in Mekong Delta.
Snubnose pompano and flathead grey mullet have a wider range of salinity tolerance. These fishes can be raised in cages. After 7-8 months of stocking, the fishes can reach 800 – 900gr harvest size.
Shrimp – Panaeus Vannamei has been an important export seafood item to Vietnam for many years. Vananmei can grow well in salinity of 5 – 30‰. Nguyen Thanh Yen, Vice Chairman of Phu Huu Commune People’s Committee, Dong Nai province said the commune has transferred 10 hectares of rice farms to shrimp ponds. As planned, the commune will transfer another 50 hectares of salt intruded rice farms into shrimp ponds. “We are building the infrastructure system for new shrimp farming area, including energy sources, roads, irrigation system to facilitate local farmers. We are also cooperating with local banks for financial support via soft loans and send engineer, technicians to provide training for the farmers,” said Yen.
Mild salinity(< 25‰) areas
Potential aquaculture species for mild salinity areas are Bostrychus sinensis, Macrobrachium rosenbergii, penaeus monodon, penaeus vannamei, rotated with rice farming.
Rice-Shrimp rotation farming: The national program of “Developing penaeus monodon, penaeus vannamei Farming Model Applying VietGAP, period 2014 – 2016″, launched by The Ministry of Agriculture and Rural Development (MARD) has seen positive results in some provinces in Mekong Delta: productivity of penaeus vannamei farms reaches 10 tonnes per hectare while panaeus monodon reaches 3 tonnes per hectare. All the shrimps in this program are certified with VietGAP and fetch 10 – 15 percent higher than non-VietGAP certified shrimps in the market. Switching from complete rice farming to rice-shrimp rotation farming can reduce environmental risks and bring more benefits to the farmers.
Panaeus monodon and Macrobrachium rosenbergii can be farmed in rotation with rice in freshly affected areas. The best stocking time for shrimp is between February and August while for rice is between September and December.
There are 80.000 hectares rice fields in Mekong Delta that can be transferred to rice-shrimp rotation farming. The MARD has just approved the project of “Applying rotation farming model of Panaeus Monodon and Rice in coastal provinces in Mekong Delta, period 2016 -2018”.
This model has been successfully applied in some provinces such as Soc Trang, Bac Lieu, Ca Mau and Kien Giang.
Bostrychus sinensis is a high value fish that has just been kept in captive environment in recent years. The harvest size of the fish can reach 12 – 19 kg per fish. Cohabitation of Bostrychus sinensis with panaeus monodon or panaeus vannamei at a density of 5 – 10 fishes per square meter has been successfully applied in Nam Dinh and Soc Trang provinces.