CATDOLL : CATDOLL: What fertilizer to use in crab ponds in summer

1. What fertilizer water should be used in crab ponds in summer?

Fertilizer water is to replenish the ammonia nitrogen, macro elements and trace elements that are consumed or lacking in the water and are beneficial to the growth of aquatic plants. Commonly used fertilizers are organic fertilizers such as animal feces and wood ash, and chemical fertilizers such as superphosphate urea diamine. Crab ponds require moderately fertile water, not too fertile or too thin, and the best is emerald green water with fresh and tender water. The method of fertilizing crab ponds is mainly to put in sufficient organic fertilizers in spring, supplemented by superphosphate in summer and autumn.

2. 2020-04-07

There are four main forms of crab farming in my country: pond farming, lake farming, river farming and rice field farming. Among them, pond farming is the most common. Below I will introduce to you how to manage pond crab farming. Please refer to it.

1. Water Quality Management

Pond cleaning and disinfection: Generally, quicklime is used to clean and disinfect the pond 15 days before stocking, which can kill harmful organisms, increase the calcium ion content in the water, and promote the molting and growth of river crabs. In the early stage of breeding, farmyard manure, inorganic fertilizer, and amino acid fertilizer can be used in combination. Appropriate use of algae species, the algae in the pond is single, easy to fall over, and the water quality is unstable.

2. Aquatic Plant Management

River crabs usually live in caves and like to hide in rocks or water plants. We can plant or transplant some water plants to help crabs hide in seclusion, and they can also play a good role in purifying water quality and hiding from enemies. The main types of water plants are Vallisneria, Water Peanut, Duckweed, Water Hyacinth, Water Lettuce, Duckweed, etc. Do not cultivate more than one-third of water plants in the water and pay attention to oxygenation, because water plants can both increase oxygen and absorb oxygen, so as to avoid hypoxia in river crabs. Planting water plants is an important management method to improve the survival rate of river crabs.

3. Feeding Management

Crab is an omnivorous aquatic animal. Phytoplankton, zooplankton, aquatic plants, and benthic animals are all crabs' favorite foods. River crabs are sensitive to fragrance, sweetness, bitterness, saltiness, and odor. During the breeding period, river crabs should be fed with high-protein feed to meet the development of their gonads. Algae Gold is rich in a variety of natural algae, and it tastes fresh and is a favorite of crabs. The protein content is suitable for the needs of river crabs, and there is sufficient animal protein. After feeding, river crabs gain weight, and the meat is delicious and nutritious. Feed more when the weather is clear, feed less on rainy days, and stop feeding in hot and humid weather before a shower without wind. If the water is clear, you can feed normally. If the water is turbid, reduce feeding appropriately and add new water in time.

4. Escape Prevention Management

There are mainly three types of fences: cement brick wall, calcium plastic board fence, and polyethylene mesh fence. At present, calcium plastic fence is widely used. The calcium plastic board is buried 20 cm in the soil along the four sides of the ridge and compacted, and fixed with wooden stakes at intervals of 1 meter to prevent crabs from digging holes and escaping.

5. Protect the crab's hepatopancreas

The hepatopancreas is the largest digestive and absorptive organ of river crabs, and is responsible for the operation of the whole body's functions. Problems with the liver endanger every part of the river crab, causing irreversible consequences. Regular use of bile acid for liver care can enhance the health of the hepatopancreas, improve disease resistance, and increase survival rate.

3. How to fertilize the crab pond in the early stage of hairy crab farming

Inorganic fertilizer: rich in inorganic nutrients such as nitrogen, phosphorus, potassium, etc. needed by algae and aquatic plants; currently commonly used are urea, carbon ammonia, compound fertilizer, phosphate fertilizer and potassium fertilizer.

Advantages: Nutrients are released quickly in the water body, reaching very high concentrations in a short time, and the water is fertilized quickly.

shortcoming

1. Too high nutrient concentration in a short period of time can easily lead to excessive reproduction of algae in the water and water concentration.

2. If nutrients cannot be quickly absorbed by algae, it will easily cause an increase in ammonia nitrogen, nitrite, etc. in the water.

3. The nutritional ingredients are single and the fertilizer effect lasts for a short time.

4. Improper fertilization can easily lead to massive reproduction of cyanobacteria, naked dinoflagellates, etc.

Organic fertilizer: organic waste liquid obtained through fermentation or industrial extraction of organic matter such as livestock and poultry manure; currently commonly used are chicken manure, bird droppings, amino acids, etc.

Advantages: comprehensive nutrition and long-lasting fertilizer effect.

shortcoming

1. Nutrients need to be fully decomposed by microorganisms before they can be absorbed and utilized, and fertilizing and watering takes a long time.

2. Livestock and poultry manure and other materials are prone to carry pathogens and antibiotic residues, causing secondary pollution to pond water.

3. Decomposition requires consumption of dissolved oxygen in the water, which can easily cause dissolved oxygen deficiency.

4. Anaerobic decomposition can easily cause an increase in ammonia nitrogen and nitrite in water bodies.

4. How should the water be fertilized before the crab seedlings are put into the pond?

Precautions for stocking crab seedlings: stocking should be done in rainy and cold weather as far as possible. After stocking, shake the water plants to let the crab seedlings swim freely. Because long-term high-density transportation can cause damage to crab seedlings and bacterial infection, it is best to soak them in "high-efficiency sterilization iodine" diluted at a ratio of 1:200 for 10 to 15 minutes before stocking crab seedlings to kill bacteria and prevent infection.

Introduce several methods of breeding crab larvae and juveniles.

1. Cage culture of crab larvae

1. Net cage production: The net can be made of polyethylene mesh or nylon mesh, with a length, width and height of 2, 1, 1 meters, or 4, 2, 1 meters, or 4, 3, 1 meters, and a mesh size of 0.8-1 mm. The net cage is supported by bamboo and other materials around it to open the box. The net cage should be covered, and a zipper should be sewn on the junction of the cover and one side. It should be closed at ordinary times and opened when feeding or checking.

2. Cage setting: The cage should be set up in a non-polluted lake, reservoir, river, or deep pond, preferably with micro-flowing water to maintain a high level of dissolved oxygen. The cage should be about 20 cm above the water surface and 80 cm submerged in the water, with a cage distance of 3-5 meters. Plants such as water hyacinth, water lily, and water peanut should be placed in the cage, generally occupying about half of the area of ​​the cage, or about 1 kg of fresh grass per square meter to facilitate the attachment and habitat of crab larvae.

3. Release of crab seedlings: The stocking density varies greatly in different regions and at different times, ranging from 5,000 to 20,000 crabs per square meter, and generally around 10,000 crabs per square meter.

4. Feeding: The basic requirements are that the bait should be nutritious and fresh, the particle size should be medium, and the feeding amount should be sufficient. You can choose to feed soy milk, egg yolk, or finely processed snails and mussels, or crushed granular bait for feeding. You can also fish out zooplankton (red worms), water earthworms, etc. for feeding. Feed 3-4 times a day, and the daily feeding amount can account for about 50% of the body weight of the crablets. As the crablets continue to grow, it can account for 10%-15% of the body weight in the later stage. The bait should be sprinkled on the stems and leaves of water plants and fed evenly.

5. Daily management: Check the nets frequently to see if they are damaged to prevent the escape of seedlings. Wash the nets regularly to prevent the mesh from being blocked, which will cause poor water exchange inside and outside the boxes. Prevent water rats, water snakes, etc. from entering the boxes to harm the crab seedlings. After 20-40 days of cultivation, the crab seedlings will develop into 3-5 stage crablets, which should be harvested in time and transferred to earth ponds for the cultivation of young crabs to avoid cannibalism due to the large size difference in the box, which will affect the survival rate.

2. Cultivating crab larvae in cement ponds

1. Cement pool conditions: The area is generally more than 10 square meters and less than 100 square meters, the pool depth is about 1 meter, and the pool shape can be square or round. The water quality should be fresh and the water source should be sufficient. There should be inlets and outlets in the pool, and they should be blocked with mesh to prevent the escape of seedlings. Some broken bricks and tiles can be placed at the bottom of the pool, and then aquatic plants can be added to facilitate the habitat of crab larvae. The upper part of the pool wall should be smooth, and the edges of the pool should be covered with plastic film to prevent escape.

2. Disinfection and fertilization of cement pools: Newly built cement pools must be soaked in clean water for several days and the water must be changed several times before crab seedlings can be released. Old ponds must be washed with 100ppm bleach solution before releasing the seedlings. After 5-7 days, fill with 40-50 cm of water, apply an appropriate amount of fertilizer, and cultivate plankton in advance to prepare a good ecological environment and bait basis for the crab seedlings to be released into the pond.

3. Release of crab seedlings: In cement ponds with average conditions, 5,000 to 6,000 crab seedlings can be released per square meter. In cement ponds with better conditions, where water can be changed frequently or where micro-flowing water can be maintained, about 10,000 crab seedlings can be released per square meter.

4. Feeding and management: Although fertilization is applied to cultivate plankton before crab seedlings are put into the pond, it cannot meet the needs of crab fry growth and development. It is also necessary to feed a certain amount of nutritious bait. Soy milk, soybean powder, fish meal and other baits can be sprinkled 2-3 times a day, and the daily feeding amount is about 20%-30% of the weight of crab fry. Pay attention to evenly sprinkle, and throw more on the leaves of aquatic plants. At the beginning, the water is shallow. In order to maintain rich dissolved oxygen and good water quality, water should be added or changed frequently. In the later stage of cultivation, the depth of the pond water can be gradually increased to 70-80 cm.

3. Cultivating crablets in earthen ponds

1. Earthen pond conditions: The area should not be too large, preferably several hundred square meters to thousands of square meters, the pond should be about 1 meter deep, and the water depth should be 70-80 centimeters. Long shape is preferred. The pond bottom should be flat, with little silt, no water leakage, solid embankment, sufficient water source, good water quality, and convenient water in and out.

2. Disinfection of earth pond: 15-20 days before stocking crab seedlings, drain the pond water, expose the bottom of the pond to the sun for a few days, then fill it with water, and then disinfect it with quicklime, bleaching powder, etc. to kill harmful organisms. The amount of quicklime used is: when the water depth is 0.5 meters, 60-80 kg per 667 square meters. If bleaching powder is used, the concentration of the pond water is 20ppm. The drug should be fully stirred and evenly sprinkled.

3. Fertilization: 5-7 days before the crab seedlings are put into the pond, fertilizers should be applied to cultivate bait organisms so that the crab seedlings will have a palatable natural bait after they are put into the pond. Generally, 150-200 kg of fermented cow dung, pig dung, human feces and urine can be applied per 667 square meters.

4. Release of crab seedlings: The density of crab seedling release can be determined based on factors such as earth pond conditions, bait supply, pond specifications and management level. Currently, 1.5-2 kg of crab seedlings are generally released per 667 square meters, and 2-3 kg can be released under good conditions.

Due to the large area of ​​the earthen pond, it is difficult to feed evenly, and the crab fry in the later stage often vary in size. Therefore, the same batch of crab fry should be placed in each pond, and the specifications should be consistent.

5. Feeding and management: When crab seedlings are put into the pond, they can use some natural bait, but it is difficult to meet the needs of the entire growth period. Feed should be supplemented in time. In the early stage, soybean milk, egg yolk and fish paste can be used as the main feed. After a week, the feed varieties can be expanded to bean cake, wheat bran, small fish and shrimp, snail and mussel meat, earthworms, etc. Grind the above feeds, add water to make a paste, and evenly sprinkle them in the early stage. This is to feed at fixed points around the earth pond, and place the feed in shallow water or on attachments such as water plants. The daily feeding amount can be controlled at 10%-15% of the total weight of the crablets, and can be adjusted to about 10% in the later stage. Feed once every morning at 7-8 am and evening at 6-7 pm, mainly in the evening, and the feeding amount can account for 60%-70%. The specific daily feeding amount should be flexibly controlled depending on the feeding of the crablets and weather conditions.

When the crab seedlings are put into the pond, the water depth can be kept at about 50 cm. The water in the pond will heat up quickly under the sunlight, which is conducive to the reproduction of natural bait organisms and the growth of crab larvae. To maintain good water quality, water should be added every 3-5 days, and 5-10 cm should be added each time. If the water quality deteriorates, the water should be changed in time. It is also necessary to prevent water snakes, frogs, etc. from entering the breeding pond to harm the crab larvae. After 20-40 days of cultivation, the crab larvae's adaptability is greatly enhanced. At this time, they can be caught and continued to be cultivated in another pond for young crabs or used for direct cultivation of adult crabs.

The above three methods of crab fry cultivation each have their own advantages. Cages are used to cultivate crab fry, because water exchange is convenient, the dissolved oxygen content in the water is high, the density of crab fry is large, the crab fry grows fast, and the survival rate is high; cement ponds are used to cultivate crab fry, and the stocking density is also large, which can save the area of ​​the cultivation pond and is more convenient to catch crab fry; earth ponds are used to cultivate crab fry, which is relatively simple to operate, and some fish fry ponds and fish fingerling ponds can be slightly modified to cultivate crab fry. After the crab fry cultivation stage, the survival rate of stage 3 crab fry is generally 30%-40%, and the survival rate of stage 5 crab fry can also reach about 30%.

4. Juvenile crab cultivation

After the crab seedlings are cultivated in cages, cement pools or earthen pools, the specifications of the crab seedlings out of the box (pool) are generally 3,000-5,000 crabs/kg. In order to further improve the survival rate, the crablets are often cultivated into 100-200 crabs/kg of juvenile crabs, which are called seed crabs or buckle crabs. Juvenile crab cultivation is mostly carried out in ponds.

1. Juvenile crab pond conditions: The area is generally 700-2000 square meters, the pond is about 1.5 meters deep, and the water source is sufficient, the water quality is good, the injection and drainage are convenient, and there is less silt on the bottom of the pond. In order to facilitate the capture of juvenile crabs, the bottom of the pond is inclined from the water inlet end to the water outlet end, with a height difference of 10-15 cm at both ends. Anti-escape facilities should be built around the juvenile crab pond.

2. Clearing the field, disinfection, and planting grass: Carnivorous and omnivorous fish, frogs, etc. must be completely removed from the ponds where young crabs are to be raised. Disinfection should be carried out 7-10 days before the crabs are put in, and wild fish should be prevented from entering the pond when adding water a week later. Water plants should be planted at the bottom of the pond, such as Vallisneria, Hydrilla verticillata, and Potamogeton. Water hyacinth, water peanut, water lily, etc. can also be transplanted, with a coverage rate of about 30%. Water plants can provide a concealed environment for young crabs, and can also be used as part of the feed. Broken bricks and tiles can also be placed at the bottom of the pond for young crabs to inhabit.

3. Release of crab larvae: 3,000-5,000 crab larvae/kg, 30,000-40,000 crab larvae can be placed per 667 square meters, 8-10 kg, 45-60 crabs per square meter. After 4-5 months of cultivation, the crab larvae out of the pond can reach 5-8 grams, that is, 120-200 crabs/kg.

4. Feeding and management: The cultivation of young crabs is in the high temperature season from June to September. They eat vigorously and are active frequently, so it is very important to do a good job of feeding and management.

① Feeding: Feed should be fresh, palatable, and evenly distributed. In the early and late stages, more animal feed can be fed appropriately, and in the middle stage, plant feed should be mainly used. Animal and plant feed should be reasonably combined for feeding. The daily feeding amount should account for 5%-10% of body weight. A feeding table should be set up, and fixed-point feeding should be combined with scattered feeding. Feed should be thrown above and below the water level, and feeding should be mainly done in the evening.

② Pay close attention to changes in water quality and keep dissolved oxygen in the water above 5 mg/L. Add water or change water frequently, usually once every 3-5 days, and deepen the pool by 10-15 cm each time. If you change water, you can first remove 1/4-1/3 of the pool water and then add new water. It is necessary to maintain good water quality and keep the water level relatively stable. At the same time, add quicklime every 15-20 days in summer, with a dosage of 10-15 kg per 667 square meters each time, which can prevent diseases and supplement calcium, which is beneficial for the molting of young crabs.

③Daily management: Do a good job in preventing escape, disease and predators. Pay attention to pond inspections, find problems and take measures to solve them. Adjust the amount of feed in time according to the development of the young crabs.

The above content is for reference only.