Determining that this is a new model, the selection of pilot households as well as implementation, inspection organization of technology transfer is paid attention a lot. Through the inspection of the infrastructure conditions of the breeding area, investment ability, technical level, the organizers have agreed to select 02 households as pilots which are Mr. Ho Sy Tai (at 12 villages, Dien Chau commune, Dien Chau district) with an area of 2,000 m2, stocking 240,000 seedlings at P12 size and Mr. Nguyen Van Khanh (at village 6, Quynh Minh commune, Quynh Luu district) with an area of 1,500 m2, raising of 180,000 shrimp seedling at P12 size.
After 92 days of farming at Ho Sy Tai farm, the survival rate of shrimp was 80%, the size of shrimp reached 60 shrimp / kg, yield of 16 tons / ha / crop, the total output of shrimp was 3.2 tons. With the price of 130,000 VND / kg, his family collected about 416 million VND, after deducting expenses such as seeds, food, electric aeration, disease prevention, pond depreciation, net profit was VND 146 million.
At the household of Mr. Nguyen Van Khanh, after nearly 4 months of culture, the shrimp reached the size of 50 shrimp / kg, the survival rate of 90%, the yield reached 21.6 tons / ha, the output was 3,240 kg. With an average selling price of 143,000 VND / kg, the household owner earned 463 million VND, after deducting expenses of VND 313 million, net profit was VND 150 million.
From the implementation of the model, some lessons learned are as follows:
1. Households: Households selected to build demonstration farms must be enthusiasts with farming, having cooperative and studious spirit. On the other hand, there should be potential for suitable water surface area and counterpart fund.
2. Breeding location: Must be located in the aquaculture planning area. The site of shrimp farming according to Biofloc technology must have separate water supply and drainage system; settling raising ponds and reservoir ponds. Ponds must not be leaking, smuggling and landslides; At least 60-70% of the total area is used to treat water and kill pests before putting water into the pond, actively supply water for ponds when necessary. There are ponds containing mud, toilets and workers' houses in order to ensure that the solid and liquid wastes from the stage of pond preparation to the stage of wastewater treatment at the end of the crop, the daily-life waste of workers and farmers do not pollute the environment of the breeding area and surrounding environment, prevent the disease from spreading and ensure food hygiene and safety. The food store, chemical storehouse and material warehouse are designed in strict accordance with regulations, properly preserved, avoiding risk of unsafe food hygiene for aquaculture. In addition, the pond location should meet the technical requirements such as near the quality water source, on a sandy soil area, soil with pH> 6, far from agricultural and industrial waste water, etc. Being equipped sampling system for water quality like pH, oxygen, ammonia, NH3, NO3, salinity, etc. and other equipment for the production of each specific pond.
3. Preparation of pond before stocking
The household used 100% of probiotics during the culture process. Ponds were prepared followed the instruction of technical staff. Then, floc could be made by probiotics with Bacillius SP strain.
Note: For this model, the aeration machine must operate continuously 24/24 unless stopping Floc and siphon. For aeration machine, daily running 50% capacity, and 100% at night (usually 4 rigs) and only off when feeding.
4. Stocking shrimps
Purchasing free – disease shrimp seedlings from reputable establishments with negative test for MBV pathogens, white spots, yellow head, taura, IMNV, hepatopancreas necrosis, etc. The size of white leg shrimp is P12 or up.
- Shrimp seed testing
+ Salinity: Take 40-50 shrimps into a glass jar containing 300 ml of water. Down salinity to 15 ‰ for 30 minutes, seed is satisfactory if survival rate is 100% shrimp.
+ Formal shock: Take 40-50 seedlings into a cup, add 100 ml of formalin solution for 30 minutes, shrimp seed is satisfactory if survival rate is 100%.
- Densities depend on the actual conditions of each household, but with the condition in Nghe An province, it is only appropriate to stock up less than 100-120 fish / m2. The shrimp seeds are stocked early in the morning or in the evening. Before stocking, the aeration machine should run from 8-12 hours to ensure that dissolved oxygen in the pond is greater than 4 mg / l. Balancing the water temperature between seed bag and pond by floating the seed bag on the pond surface for 5-10 minutes, then slowly put the water into the bag, holding the bottom of the bag slowly backward so that shrimps will slowly go into the pond.
5. Care and management
In industrial shrimp farming, food accounts for 60-70% of the total cost. Therefore, the decision to use feed and feeding method is the key to great economic effect.
According to the piloted households, they feed the shrimps according to the instructions. In addition, depending on the real situation (shrimp health, moulting cycle, weather, etc.) and monitoring shrimp feeding when the shrimp 20 days or more to adjust and manage the feed accordingly, avoid missing or over-feeding. Feed 4 times a day. Use of permitted feed under the Vietnamese regulation, with clear labels, quality information, appropriate nutritional content, protein contained at least of 32-38%. Proper feeding, avoiding overfeed, using suitable feed size for each stage. Regularly monitor the survival rate, growth rate and quantity in each pond to adjust the feed quantity accordingly.
Depending on the market situation (demand, price, shrimp size, etc.) to decide the harvest. It should be collected when the size of shrimp reached 100 head / kg to scatter shrimp quickly. The best time to harvest is 7-10 days after shrimp shedding.
Harvesting depends on the conditions of each region. It can be collected directly through the sewer or pump or drainage of water and pull the net. Harvest time is as short as possible.
The containers and means of transport must be cleaned. Ice is used at the premises with food safety. The temperature during transportation and storage must be lower than 4oC.
After harvesting, the ponds must be disinfected and the farmer has to stop farming for at least 30 days between two crops.