In recent years, especially in 2002, the majority of production sites from the south to the north had the phenomenon of lack of crabs, which was mainly due to the low rate of holding eggs and the low survival rate of overwintering. In order to ensure the quality and quantity of parent crabs used for nursery production, the following technical points should be mastered during mating and wintering. One, crab selection The so-called pro-crabs, that is, the male and female green crabs whose gonads have matured and have not yet mated, when the yellow crab shelled into green crabs, it marks that the crab has entered sexual maturity. The ovary of the female crab develops rapidly, and the male crab is also gradually sticking to the testis. Thick, under natural conditions, crabs have already begun to genital migration, this is a good time to pick a crab. The choice of pro-crab should be selected in the pond of the river and lake. It should not be picked in the hands of traders. Specific selection criteria should grasp the following points: Second, timely mating The eggs of crabs have matured from yellow crabs to green crabs with strong sensitivity and can be incorporated into sperm once the external conditions are appropriate. Therefore, the post-acquisition intensive cultivation phase should be carried out in freshwater. Otherwise, long-term cultivation in the seawater (referring to male and female cultivating) will cause the gonads (eggs, sperm) to age due to excessive stimulation of salinity for a long time. Salinity is a necessary condition for mating of crabs. Sexual crabs will be estrus by contact with seawater and will normally hug eggs after mating at salinity between 12 ‰ and 25 ,, but their egg holding rate will drop significantly when salinity is less than 8 ‰. And there will be a large number of yellow eggs (dead egg) crabs. When the water temperature reaches the appropriate temperature for mating and spawning 8-14°C, the male and female crabs can be placed in the same pond for mating. Excessively high or low temperatures (above 15°C or below 6°C) prone to miscarriage after mating, ie eggs cannot adhere to the bristles of the oviduct and abdomen. Third, daily management In the process of intensive cultivation of pro-crabs, the first mastery should be carried out in fresh water. However, most breeding sites are on the seashore. Despite the use of fresh water, the water still contains certain levels of salinity. Therefore, in this case, males and females should be reared separately to prevent mating under low salinity. Unpaid feeding should be based on animal feed, such as fish, snails, etc., the amount of feeding according to the weight of 3% -5%, and depending on their eating and drinking conditions increase or decrease. At this time, the water depth is controlled at 80-100 cm, and the water is replaced once every 5-7 days, and the amount of water exchanged is not less than 1/3. After 6 days of mating, the male crabs were removed, the quality of the shirt tunnel body and the good egg hug were placed in the winter in the winter pool, and the stocking density was 2-3/m2. At this time, the water temperature should be moderate. Less feeding, plant-based foods such as soybeans, carrot 1, sweet potato and so on. The wintering pond area is preferably 1000-1500 square meters, and strictly sterilized in clear ponds. The silt in the pool must not exceed 5 cm. Sandy ground is preferred. If the mud texture is about 5 centimeters in the pool, it will be in the wintering pond. Zhong Jian is 40 cm wide and 20 cm deep. It is also known as "Tian" or "well" shaped crab ditch. It is also possible to put some arched tiles, circular porcelain pipes, etc. in the pool. The depth of water storage in the wintering pond is not less than 1.5 meters, and the depth of water in the winter is 1.5-2 meters. Before the seal is frozen, change the water every lo- 15 days and ask for isothermal salt. After the ice is sealed, in order to prevent oxygen deprivation, one must open a ice belt about 1 meter wide around the pool or place a reed in the pool every day, one for every 10 square meters, in order to keep the ice water and the air transparent. 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1 must be Erqiu crab;
2 The body weight should be between 100-125 grams per male. The male crab should be slightly larger than the female crab.
3 shell green belly white, hard shell without trauma;
4 The appendages are complete, lively and robust, with no parasite on the body surface;
5 Select time The northern region is from the equinox to the frost, and the southern region is before the beginning of the winter after the frost.
6 Male to female ratio is generally (2.5~3): 1