In recent two years, with the maturity of aquatic plant protection technology and the increase of breeding density, the value of large-scale crab-detaining to cultivate larger-scale adult crabs has been increasingly recognized by crab farmers. Therefore, many crab farmers who want to raise high-quality crabs are keen to choose 30-60 large-size crab seedlings. Although it has become a knowledge in the industry to cultivate large-scale high-quality crabs with large-scale buckle crabs, why do many crab farmers choose to breed large-scale buckle crabs, but the ideal adult crabs have not grown up? The emergence of different factors such as weather diseases and nutrition will lead to some old seedlings, few seedlings and sick seedlings. Therefore, when purchasing seedlings, we should choose seedlings with uniform individuals, clear traditions, no broken limbs, no enteritis in the body and abdomen and good vitality. From the appearance, it is important that the intestines in the body and abdomen are red and black when they disintegrate. If you crawl quickly on the aquatic plants and are disturbed, you will quickly dive into the bottom of the pool. This is a healthy seedling liquid.

Choose the pit 1 that large-sized crab seedlings need to avoid, which is a large-sized crab species raised in coastal low salinity waters. This kind of crab is precocious, and it is difficult to raise large-scale adult crabs in practice even if the environment is good.

Pit 2: Large-scale Eriocheir sinensis raised in shallow water nursery pond (water depth about 50 cm). This kind of crab has high accumulated temperature in seedling stage and high early maturity rate in adult stage. The proportion and quantity of large-scale quality crabs can be less.

The third pit: large-scale Chinese mitten crab raised by parents with big eyes and small eyes. Due to genetic reasons, this Chinese mitten-handed crab has a high maturity (reduced molting times) and a small turnover rate in the breeding process, so it is difficult to cultivate large-scale high-quality crabs.

The fourth pit: large-scale crab, high maturity, close to the old crab. Because 2-4 shells will mature in the second year, it is difficult to cultivate large-scale crabs. The main identification method is to comprehensively evaluate the coverage rate of abdominal nail and the situation of large chelating villi.

Several kinds of crabs that are not suitable for selection. It is not advisable to buy hairy crabs cultured in greenhouses. In coastal areas, it is suitable to use greenhouse to cultivate early-breeding megalopa to early-breeding crab, and to use early larvae to breed crabs in the same year. Although the standard of this farming model is not big, it has high yield, high survival rate and shortened farming cycle, so it is also very popular at present. However, it is not our inland waters that breed and sell the early larvae, because the accumulated temperature of the early larvae is high and the salinity of the living waters is relatively high. After entering inland waters, the growth specifications are small and the survival rate is low.