First,? Selection of aquaculture ponds
The earth pond is the best, and the structure of the pond is similar to that of the semi-intensive shrimp pond. The existing shrimp ponds can also be used to cultivate swimming crabs. Small and medium-sized areas are suitable, and the water depth is1.5-2m. In order to maintain good water quality, aquaculture ponds should be able to fully exchange water. Portunus likes to inhabit along the pond, so the slope area should be increased as much as possible to avoid excessive density. It has the habit of submerged sand. The bottom of the pool is paved with medium-coarse sand with a thickness of 10 cm, and a small sand pile is made to let it perch on submerged sand. In order to reduce cannibalism, we should also build a hidden place for swimming crabs with stones and tiles at the bottom of the pool.
Second,? Preparation before seedling release
Before stocking, drain the pond water, expose the bottom of the pond, and remove the aquatic animals that devour crab seedlings. You can also use quicklime to clean the pond. When the water depth is below 10 cm, 75 kg of quicklime per mu will turn into lime milk and splash all over the pond. After 7- 10 cleaning, water can be injected into the pool, and a 60-mesh conical filter screen is set at the water inlet to prevent enemies and pests from entering.
Third,? Seedling stocking
(1) Stocking time: When commercial crabs (about 250g) were cultivated in that year, we should grasp the word "made" and make full use of the first batch of Portunus. However, it should be noted that the seedlings of the same specification must be kept in the same breeding pond to reduce the chance of cannibalism and improve the survival rate.
(2) Stocking density: In the pool with clean bottom and good water exchange conditions, the initial seedling density is 2000-3000 plants/mu, and the growth and survival rate are good. Too high or too low density will affect growth or survival rate. After the Mid-Autumn Festival, if the adult crabs that are not shelled are stored in small noodles, they will be put on the market in winter after a short-term breeding period, and the stocking density is about per square meter 10 kg.
Fourth,? Feeding and management
1. Feeding: Portunus trituberculatus mainly uses animal feed, and feeding low-value shellfish is the best way for large-scale culture, followed by fresh miscellaneous fish. The daily food intake of young crabs weighing 0.8 grams is 80% of their body weight, that of individuals weighing 30 grams is 20% of their body weight, and that of those weighing more than 50 grams is about 10%. People who weigh less than 20 grams are actively feeding during the day and at night, and those who weigh more than 20 grams are only engaged in feeding activities at night. So feed it 2-4 times a day 20-30 days after the start of breeding, and then feed it once a day at night along the pond wall.
2. Water quality management: The survival rate of crystal clear ponds is low, and proper fertilization should be applied during the cultivation process to make the transparency of pond water about 30 cm. In addition, we should insist on changing water every day. Crabs consume a lot of oxygen during molting. If the water is not changed in time, they will die of lack of oxygen. In the process of culture, the water temperature should be 17-30℃. Exceeding 30℃ will lead to death. If it is lower than 15℃, it will affect the crab's feeding, or even stop eating. Salinity should be above 20‰, and it will kill you if it is below 20‰.
3. Separate feeding of male and female: The reproductive rate of mixed feeding of male and female is extremely poor, and the price of female crabs is more than 2 times higher than that of male crabs in winter. Therefore, if possible, in the process of mating, females and males can be raised separately. Male crabs can leave the pool at any time after reaching the commodity specifications, and female crabs can mature regardless of mating or not, and can be kept until the ovaries mature in winter. ?