How to promote the growth of crab shell

Crabs grow by relying on shells. Each time the weight of the shell increases by about 20%. However, some fish farmers often encounter the problem of dead crab shells. In addition to the crab species not adapted to the local water environment, factors related to shelling include feed nutrients, water pH, pond conditions and crabs. The species itself is related to sexual maturity. In this case, taking the Yangtze River as an example to promote smooth crab shells should pay attention to the following aspects. (A) Serious selection of river crab species in the Yangtze River system also has advantages and disadvantages. In addition to picking off non-Yangtze, it is also necessary to remove already mature Yangtze River varieties where the first side tooth exceeds the eyelids and those below the eyelids are all non-Yangtze. Where the navel (female) covers the entire plastron, And the edges that grow fluffy are already mature. Males are also mature in the group. When necessary, the galacula can be observed. The mature (female) ovary is purple and even the ovules are visible. Mature (male) white semen is the most reliable method. If they accidentally mix with sexually mature crab species, the Metropolis will die without shelling, and the more it mixes in, the more it will die. (b) The physical and chemical factors regulating water quality and water quality are the first elements of the growth of crab shells. Adapting the water quality of crab shells requires a pH of between 7.5 and 8.5, ammonium nitrogen within 0.1 to 0.4 mg/l, and a fresh water environment with dissolved oxygen above 5 mg/l. The pH of general pond water is between 6.5-7, even 6.5; ammonium nitrogen is as high as 0.5 mg/l. Older fertilizers, fertilizers, and sprays with higher fatness are the most unfavorable to the growth of crab shells. The adjustment method is to first drain the original pond water by more than 1/3, and add the same amount of fresh water to keep the water quality cool and live. Every 1067 hectares will produce 10-15 kilograms of lime every half a month to adjust the pH of the pool water to make it slightly alkaline. Sex; the planting area of ​​aquatic plants in ponds accounts for more than 30% of the water surface of the ponds, so as to absorb pond fertilizers to clarify the water quality, which is conducive to climbing crabs, feeding and helping clam shells; setting up gentle slopes in the leeward sunny areas of the pool for heating crabs, Foraging, clam shell; no organic nitrogen fertilizer in the hot season, can apply inorganic nitrogen fertilizer with inorganic phosphate fertilizer. Depending on the amount of water and fat as appropriate. Each time every 0.067 hectare of 1 to 1.5 kg, so that ammonium nitrogen does not exceed 0.45 mg / l; bottom sludge more than 20 cm to remove a part, to keep within 10 cm. (C) to strengthen the feeding of crabs before the oyster shell, still need more nutrition to grow before and after the supply of oyster shell, regardless of the specifications need to increase the proportion of animal feed, can promote their groups to synchronize as much as possible shell. Guarantee the content of crude protein in feed. Can be fed full price pellet feed if conditional. The amount of feeding depends on the cultivation specifications. Breeding crabs, not more than 5% of the overall weight of the crab, can prevent excessive nutrition and premature; to cultivate crabs, you can vote for more than 10% of its total weight of the crab, as far as possible to eat, eat, promote Shell growth. (D) Prevention and control of diseased crabs Inhabited waters, regardless of ponds or rice fields, before the release of the species, all need clear ponds to disinfect, kill pathogens, where can drain the pool, as far as possible after draining Qingtang, every 0.067 hectares Quick lime 100 ~ 150 kg, dissolved and evenly spilled throughout the bottom of the pool and the surrounding bank slope. This is particularly necessary for the cultivation of crab ponds. After releasing the crab species, if parasitism is found, it should be promptly given medicine.

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