When will the cultured river crabs be released?
In spring (the end of March and the beginning of April), the best stocking time is when the water temperature reaches above 8℃, and the crabs can be eaten immediately after entering the pool, which can improve the first survival rate of crabs.
Before releasing crab seedlings, the following preparations should be made:
1. Detoxification: With the increase of culture time, the proportion of pond-clearing drugs (polyester, organophosphorus, etc.) increased. ) Farmers use it more and more. With more and more newly opened fish ponds, pesticide residues in farmland are heavier. Even if you soak in the pond for a long time after reclamation, the pesticide residues in the soil will be released with the change of time and temperature. Therefore, the most important task before releasing seedlings is detoxification. Fill the pond with water, sprinkle Jieduling all over the pond, release water after three days, and put it to the ditch water level of 60 cm to 80 cm. Then use Jieduling to detoxify. If there are many drugs used to clean the pond at the mouth of the pond, it is recommended to detoxify it several times until all the toxins are eliminated. Avoid swimming, landing and digging holes after releasing seedlings, and improve the survival rate of crab seedlings.
In the water experiment of shrimp seedlings, 10 shrimp seedlings with good quality were selected and hung on the bottom of the pond with net bags. After 48 hours, if they are not dead, they can be released.
2. Anti-stress: It takes a long time for crab seedlings to be transported out of the nursery pond before they can be put into the adult crab pond. Because the environment of adult crab pond and nursery pond is different (such as water temperature, pH value, salinity, dissolved oxygen, etc.). ), and the seedlings are immature, and it is easy to cause stress when put into a new environment. Therefore, 65438+ 0 days before seedling release, the whole pool was sprinkled with gold polysaccharide+anti-tattoo+stress hard shell spirit. Reduce stress reaction and improve the survival rate of seedlings.
3. Fertilizer and water: During seedling release, due to the low temperature and great weather changes, the seedlings eat little or no food, which makes the seedlings with poor physique easy to steal and die, resulting in the loss of crabs in the breeding process and low final yield. So how to ensure that under the uncontrollable weather environment, the water environment changes little and has the least impact on crab seedlings? Fertilizing water is one of the effective methods. Therefore, the whole pond was quickly fertilized at low temperature three days before seedling release, which contained various polypeptide components, which provided nutrition for crab seedlings, ensured their healthy growth, directionally cultivated high-quality algae, stabilized water quality, provided natural bait for crab seedlings, increased dissolved oxygen in water, effectively inhibited the growth of moss, reduced the stress response of seedlings, and reduced the phenomenon of landing and burrowing of crab seedlings after seedling release.
How much is it to breed river crabs per mu?
1. The number of crab fry per mu, that is, the density of crab fry, should be selected according to water resources, such as water depth, water flow, the number and types of aquatic plants, whether other fish and shrimp are stocked, and also according to the number of natural enemies on the water surface, the specification requirements of crab market, gender requirements, etc.
2. The density of stocking crab seedlings with different water surface types is different, which is roughly as follows. Large plain reservoir, about 1.5 meters deep, with 300 crab seedlings per mu, that is, about 4 kg; Intensive cultivation of ponds, rivers, Tang Wei, paozi and wetlands is about 10 ~ 15 Jin, and crab seedlings are about 1000; There are about 700 crabs per mu of water surface in rice fields, that is, one crab seedling per square meter, about 8 kilograms.
What are the techniques and precautions for crab culture?
1, take measures to ensure good water quality. In June, the pond water should be detoxified for 1~2 times, the pond bottom material should be improved for 2~3 times, and the pond periphery and feeding place should be improved with the bottom material improver to create a good bottom material environment. In June, all kinds of aquatic plants in the early layout of the crab pond are in the vigorous growth period. Therefore, it is necessary to do a good job in the conservation of aquatic plants and take corresponding measures as soon as possible to achieve a reasonable layout of aquatic plants in the pond and a good ecological environment in the pond, which can also reduce the workload of fishing out aquatic plants in high temperature season. Ponds planted with black algae in the purse seine should be removed according to the growth of aquatic plants, and the time is generally from the end of May to the beginning of June. Elodea nuttallii in the ring ditch should be partially removed and transplanted to prevent aquatic plants from rotting in high temperature season, causing water quality deterioration and diseases. In the process of removing Elodea nuttallii, a small amount of Elodea nuttallii should be removed several times while changing the bottom edge to prevent the overflow of toxic and harmful substances at the bottom of the pond.
2. Bait feeding and water quality management. June is the vigorous growth period of Eriocheir sinensis, and the third molting of Eriocheir sinensis basically ends in early and late June. Generally speaking, Eriocheir sinensis molts once from late June to early July. In June, the feeding amount of Eriocheir sinensis has been large, and the daily feeding amount should generally be controlled at about 8%~ 12% of its storage in the pond. The feeding focus is mainly on small fish, and the daily feeding amount of small fish is more than 2. 0 kg per mu, and it is a complete set. In some ponds where water is inconvenient, it is necessary to reduce the amount of small fish and increase the amount of bait such as pellet feed.
The water quality of crab ponds should be kept fresh, fresh, tender and cool. The water level in the crab pond should be gradually deepened according to the growth of aquatic plants in the pond, and water can be added once every 2-3 days. In mid-June, the average water level in the crab pond should reach more than 50cm. By the end of June, crab ponds are generally required to reach a higher water level, and quicklime can be sprinkled once in June to adjust the water quality. The dosage of quicklime should not be too high, and it is required to use 65438+ per meter of water depth per mu. When the temperature rises in June, the activity of river crabs increases, which may be caused by insufficient feeding or poor water quality regulation. Measures should be taken to adjust the quantity and variety of bait, adjust the water quality, raise the water level and apply fertilizer appropriately according to the specific situation, so as to keep the water fresh and the transparency of the pond water at about 50cm, which is beneficial to the healthy growth of river crabs.
3. Disease control of river crabs. June is the key period for disease prevention and control of river crabs, and the prevention and control work should be combined with bait feeding, water quality control and water ecological environment construction in the breeding process. In the use of drugs, after molting for the third time, Eriocheir sinensis is required to kill insects, take orally and use externally. The drug resistance of cultured varieties should be considered, and drugs with the same effect can be selected. In rainy season, the pond can be disinfected 1~2 times to reduce the generation of water germs. After entering June, microbial agents were widely used in crab ponds, and the application effect of microbial agents was good. They can be applied to crab ponds regularly, usually once every 7~ 10 day, which can not only adjust the water quality to maintain a good ecological environment, but also achieve the effect of preventing diseases.
Precautions before releasing crab seedlings:
1, the seeding time should be chosen in sunny morning or evening; Try to avoid stormy weather.
2. Water quality conditions (water temperature, pH value, salinity, dissolved oxygen, etc. ) and the number of feed organisms. The water quality conditions of crab seedlings in the culture pond should be as consistent as possible with those in the nursery pond (generally, the salinity difference should not exceed 5 degrees, the pH value should not exceed 0.3, and the temperature difference should not exceed 3 degrees).
3. The seedlings should be scattered, not concentrated, so that they can climb into the water independently.
4. The water body should maintain a certain fertility before seedling release, which can improve the survival rate of seedlings;
5. Soak the seedlings in pond water before launching, and use gold polysaccharide+anti-stinging+stress hard shell spirit to adapt to the environment, supplement nutrition, enhance the physique of crab seedlings and reduce loss;
6. After the seedlings go into the pond, sprinkle anti-itch and anti-stress products to reduce stress and improve the survival rate of crab seedlings.
7. After being placed in the pond for two days, the natural enemies of Vibrio were used for biological disinfection, which not only destroyed the water balance, but also provided a safe water environment and ensured the healthy growth of seedlings.
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