When will the cultured river crabs be released?
In spring (the end of March and the beginning of April in spring), the ideal stocking time is that the water temperature reaches above 8℃ and the crabs can eat when they go into the pool, which can improve the survival rate of the crabs for the first time.
Before releasing crab seedlings, the following preparations should be made:
1, Detoxification: With the longer the breeding time, the proportion of pond-clearing drugs (polyester, organophosphorus, etc.) used by farmers is increasing. With the increasing number of newly opened ponds, the pesticide residues in farmland are heavier. Even after a long period of soaking in ponds after reclamation, the pesticide residues in soil will be released with the change of time and temperature. Therefore, one of the most important tasks before releasing seedlings is detoxification. Fill the pond with water, sprinkle Jieduling all over the pond, release water three days later, and put it to the ditch water level of 60 cm to 80 cm. Use Jieduling to detoxify again. If there are many drugs used to clear the pond at the mouth of the pond, it is recommended to detoxify many times until all the toxins are completely eliminated. Avoid the phenomena of swimming, landing and digging holes after releasing the seedlings, and improve the survival rate of the crab seedlings.
In the water test of shrimp seedlings, shrimp seedlings with good quality 10 are selected, and the shrimp seedlings are hung in a net bag at the bottom of the pond. After 48 hours, if they are not dead, they can be released.
2. Anti-stress: It takes a long time to transport the crab seedlings out of the seedling pond before they can be put into the adult crab pond. Because the environment of the adult crab pond is different from that of the seedling pond (such as water temperature, pH value, salinity, dissolved oxygen, etc.), and the seedlings are immature, putting them into the new environment is easy to cause stress. Therefore, gold polysaccharide+anti-tingling+stress hard shell spirit was sprinkled in the whole pond 1 day before seedling release. Reduce stress reaction and improve the survival rate of seedlings.
3. Fertilizer and water: During the seedling release period, due to the low temperature, the weather changes greatly, and the seedlings eat little or no food, which makes the seedlings with poor physique easy to steal and die, which will lead to the loss of crabs in the breeding process and the low yield in the end. So how to ensure that the water environment changes little and has the least impact on crab seedlings under uncontrollable weather environment? Fertilizing water is one of the effective methods. Therefore, the whole pond is quickly fertilized at low temperature three days before seedling release, which contains various polypeptide components to provide nutrition for crab seedlings, ensure their healthy growth, directionally cultivate high-quality algae, stabilize water quality, provide natural bait for crab seedlings, increase dissolved oxygen in water, effectively inhibit the growth of moss, reduce the stress response of seedlings, and reduce the phenomenon of landing and burrowing after crab seedlings are released.
How much is an acre of cultured river crabs?
1, the number of crab seedlings per mu, that is, the density of crab seedlings, should be selected according to the water resources, such as water depth, water flow, number of aquatic plants, species, whether other fish and shrimp are stocked, and at the same time, the number of natural enemies on the water surface, the specifications and gender needs of the crab market, etc.
2. The density of stocking crab seedlings in different water surface types is different, which is roughly as follows. Large plain reservoir, 1.5 meters deep, with 300 crab seedlings per mu, that is, about 4 kg; Intensive cultivation of ponds, rivers, weitang, paozi, wetlands and other water surfaces is about 10~ 15 kg, about 1000 crabs; About 700 crabs are raised in rice fields per mu of water surface, that is, one crab seedling per square meter, about 8 kg.
What are the techniques and precautions for breeding river crabs?
1, take measures to ensure good water quality. In June, the pond water should be detoxified for 1~2 times, and the bottom material of the pond should be improved for 2~3 times. The periphery of the pond and the feeding place should be improved by using the bottom material improver to create a good bottom environment. In June, all kinds of aquatic plants laid out in the early stage of crab ponds are in the period of vigorous growth. Therefore, we should do a good job in the maintenance of aquatic plants and take corresponding measures as soon as possible, so as to achieve the reasonable arrangement of aquatic plants in the pond and the good ecological environment of the pond, which can also reduce the workload of fishing out aquatic plants in high temperature season. The pond where Hydrilla verticillata is planted in the purse seine should be removed according to the growth of its aquatic plants, and the time is generally from the end of May to the beginning of June. The Elodea nuttallii in the ring ditch should be partially removed and transplanted to prevent the water quality from deteriorating due to the decay of aquatic plants and causing diseases in high temperature season. In the process of removing Elodea nuttalli, a small amount should be removed several times while changing the bottom edge to prevent toxic and harmful substances at the bottom of the pond from flooding.
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 the early and late June. Generally, 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. kg per mu. Some ponds with inconvenient water intake should reduce the feeding amount of small fish and increase the amount of bait such as pellet feed.
The water quality of crab culture ponds should be kept fresh, fresh, tender and cool. The water level of crab ponds should be gradually deepened according to the growth of aquatic plants in ponds, and water can be added once every 2-3 days. The average water level of crab ponds should reach more than 50cm in mid-June. 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 amount of quicklime should not be too high, and it is required to use quicklime/kloc-per meter of water depth. When the temperature rises in June, the activity of river crabs increases, which may be caused by insufficient feeding or poor regulation of water quality. Measures should be taken according to the specific situation, such as adjusting the number and variety of bait, regulating water quality, increasing water level, and appropriate fertilization, to keep the water quality 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 carried out in combination with bait feeding, water quality control and water ecological environment construction in the breeding process. In the use of drugs, after the third molting of river crabs, it is required to kill insects, take them orally and eliminate them externally, and the drugs for prevention and control should consider the drug resistance of cultured varieties, and the drugs with the same effect can be selected. In the rainy season, the pond can be disinfected 1~2 times to reduce the generation of water germs. After June, microbial agents are widely used in crab ponds, and the application effect of microbial agents is good. They can be applied to crab ponds regularly, usually once every 7~ 10 days, 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, seedling release 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. As far as possible, the water quality conditions of crab seedlings in the breeding pond should be consistent 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 degree of fertility before releasing the seedlings, which can improve the survival rate of the seedlings;
5. Soak the seedlings in pond water before launching, and use gold polysaccharide+anti-tingling+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 down to the pond, sprinkle anti-tingling and anti-stress products to reduce stress and improve the survival rate of crab seedlings.
7. After two days in the pond, the natural enemies of Vibrio were used for biological disinfection, which not only destroyed the water balance, but also provided a safe water environment to ensure the healthy growth of the seedlings.
> > Recommended reading: How to breed crayfish in rice fields? It is very important to do these six points well!