First,The key to the success or failure of crab breeding is to prevent escape

Sleeve nets are installed at the drain outlet, the size of the net is the thickness of the water pipe, and the length is more than 1.5 meters. In low-lying areas, a gauze is set on the inside. The anti-escape wall is about 0.5 meters high from the ground, and the lower end is made into a U shape and buried 0.15 meters underground. Curved corners, no folds and no wrinkles. The bamboo pole is about 0.75 meters long, inserted into the ground for 0.15-0.2 meters, tightened with a string, and tied to the bamboo pole together. The distance between the bamboo poles in the east-west direction is 0.4 meters, and the distance between the bamboo poles in the north-south direction is 0.5-0.6 meters.

Second, the "prediction" before raising crabs

The first is market forecast: including seed price, expected product price, output, cost input, etc.

1. Cost input: seedlings, bait, anti-escape and production materials, etc., about 300--400 yuan/mu;

2. Cultivation specifications: average 1.0-1.5-2.0 two;

3. The per mu yield setting: 20 kg per mu of adult crabs;

4. Estimated output value: The average selling price is 15-20 yuan (600-800 yuan/mu);

5. The yield of crabs per mu is 40-50 kg, and the pre-storage price is estimated at 12-16 yuan (the output value is 500-800 yuan/mu);

In this way, you already know how much money you can make this year before you raise crabs.

There are three elements for raising crabs: environment, seed, and bait

(1) Environmental conditions:

The most basic conditions for cultivating large crabs include: water source, water body, water quality, light, and benthic organisms.

1. Water source: It can be stocked during the phenological period, which is a necessary condition for its prolonged growth and completion of 4 shells; it is best to enter the pond in the middle and early April, when the water temperature is about 8-12 degrees, after one to two weeks Under normal circumstances, when the water temperature is stable at 18 degrees, the shelling begins. This is guaranteed for the first shell to peak in early May. Under normal circumstances, the shelling cycle of river crabs is about one month, but after mid-July, there is only one chance of shelling, and it will not be shelled when it enters the biological maturity stage. Therefore, it is an important part of raising crabs to put it early and prolong the early growth time.

2. Water: It is the key to achieve normal growth. When the water in the temporary holding pond before the water from the field is shallow, it is necessary to set up a ring groove in the temporary holding pond, but it is not too big. In large areas, the seedlings are small and the water is shallow. In practice, an opening of 0.6 meters, a depth of 0.4 meters, and a bottom width of 0.3 meters can meet the needs of temporary cultivation to large-scale cultivation.

3. Water quality (sealing, pesticides, fertilization)

Closed weeding: In paddy fields where crabs have been raised for two years, depending on the severity of the weeds in the previous year, generally 1/2 or 1/3 of the normal dosage, there will be basically no grass shortage.

Insect control medicine: 3 days before transplanting, use "systemic agent" in the seedbed to kill rice weevil, scorpion borer and other insect pests. Before the larvae of the first and second generations of the worms burst their membranes, the normal doses of low-toxic drugs such as "Kangkuan and Matrine" were used, which did not harm the crabs.

Fertilization: 90% of the fertilizer applied before the spin. Make sure to fertilize evenly. Be sure to pay attention to the amount of supplementary fertilizer not more than 3 kg. Evenly fertilize, spin while applying, and reduce exposure time

4. Lighting: (avoidance in the early stage of the ditch, and light in the middle and later stages) The lack of light for crab breeding in paddy fields is a crucial link for the survival and growth of river crabs. Especially during the rainy season from mid-July to mid-August, the water supply time interval of paddy fields is long, and it is also the period of greatest loss. (Don't eat or drink, go ashore) It should be said that there are indeed very few big crabs raised in the rice fields. The reason is that after the rice is jointed, there is no light on the ground.

(2) Seedlings:

1. The quality of seedlings is the key to the catch rate and yield of aquaculture

a. The specifications are neat, the vitality is strong, and there is no hanging dirt; b. The plumpness is above average; C. The specifications are within 80/catties; d. The dehydration time is short; e. The wintering density is small, and the number of artificial oxygenation is small; , Untouched ponds.

First of all, the sensory standards are based on uniform appearance, complete limbs, light body color, no hanging dirt, and strong vitality. More important is the high, medium and low dehydration time and plumpness. When selecting seedlings, after confirming the appearance of the dehydration time, select representative crab seedlings with thick shells, thin shells, and medium shells to open the cover. The gonads are golden-yellow, and are approximately sexually mature. After one or two shells, they will no longer shed their shells.

2. The size of the seed is the basis for the development of large crabs

In the cultivation of adult crabs in the north, under the condition that the growth needs of river crabs are met, there are at most four shelling processes in one cultivation process. Calculated by doubling the weight gain every time the shell is taken off, only 80 crabs/catties can reach 2 taels. Among them, 80 per catty and 80 on average, the results vary greatly. That is to say, those with less than 80 animals can raise up to 2 taels, and those with more than 80 animals can not reach 2 taels.

3. The effect of dehydration time on the survival rate of crabs

No matter how good the crab seedlings are, the dehydration time and the temperature when the seedlings are transported are inversely proportional to the survival rate.

a. Hang the seedlings from the pit and spit out the mud with a cage, (the water is not very shallow and very mixed) per square meter should not exceed 20 catties, and the net should be half in the water and half in the space, and the time should not exceed 3 hours (the time is 3 hours). More than 1 hour, must be equipped with oxygen-enhancing facilities).

b. The seedlings hanging in the cages and the crab seedlings get together with local hypoxia, which causes the regeneration of the crabs to be disordered and loses the ability to regenerate new membranes. There are also joints formed by the high density, bite each other, and the body fluid condensed at the broken claw tips, which are the reasons why they cannot take off the shell and die.

c. The large crab seedlings that are caught are all right if they are temporarily raised in the pond before shelling, while the seedlings that enter the pond after shelling are more than 1 tael, and the price is not expensive, but the recovery rate is low. pitful. This is mainly due to internal injuries caused by soft shells, long dehydration time, netting, bagging, over-weighting, loading and unloading, backhanding, bumping and squeezing on the way. To select wild seedlings after shelling, first, they must go to the netting site, use solid boxes, and a small amount, especially soft shell crabs, must be transported by water.

4. Determination of the number of seeds to buy

At least 20% of the shells were unsuccessful at the first time and could not be removed. According to the release after molting once, between 300-350 crabs per mu, according to the activity space and biomass supply of 2 square meters of one crab, and the budget of 70% of the recovery rate, about 220-250 crabs can be recovered. , an average of 100 grams per piece, and the yield per mu is 42-50 catties.

The number of seedlings purchased: According to the normal year, the survival rate of different specifications varies. The catch rate of 100 crabs is 60%, 80 is 50%; 60 is 40%, and 50 is about 30%. Quantity of seedlings purchased per mu = planned yield per mu × cultivated animals/catties ÷ recapture rate + 10-15% damage.

5. The area setting of the seedling holding tank

The size of the temporary cultivation pond is determined according to the temporary cultivation time, that is to say, if it is placed in a large area before transplanting, the temporary cultivation time is about 30 to 40 days. 40kg is the upper limit.

After transplanting rice seedlings into the field, the temporary raising time is generally about 40-60 days. In a temporary raising pond with a good environment, two shells can be completed. At that time, the load of the pond will be at least 1.5 times more than when entering the pond. When the mu is temporarily raised into the pond, the amount of seedlings cannot exceed 25 kg.

6. There are currently two methods for the selection of temporary holding ponds, one is the paddy field near the canal, and the other is the drainage ditch. Note: paddy fields should keep water and ditches should be prevented from escaping. Temporary cultivation in paddy fields: Set up shelters at the edge of the ring ditch before shelling. The best effect is to use the ditch for temporary maintenance. The holding tank should be disinfected. Seedlings should be disinfected before entering the pool.

7. Secondary selection of seedlings: When the temporary cultivation is completed and placed in a large area, it is best to count and re-select the seedlings, that is, to divide the seedlings that have not been shelled out. Such seedlings cannot be shelled again if they are raised again. Even if it can be taken off, it is not certain that it will grow up.

(3) The selection and quantity of feeding materials

The food intake of river crabs just entering the pool for 3-4 days is generally 5-8% of their body weight.

1. Feed quality and weight gain: Feed quality is a sign of how fast crabs grow. The relationship between bait quality and weight gain: the area is 31-34 and 37-48mm, and the weight gain is 65-75 and 100-120%. Optional bait: more than 30 synthetic materials that can absorb crude protein or bean paste, grains, fish and shrimp, etc.

2. Quality identification of synthetic bait: a. Price identification: the price of available synthetic bait is slightly higher than that of bean curd in the same period; b. Yiyi, Erwen, Sanyao, Sipao; c. It is best to combine them with the manufacturers to make their own. Recipe made to order.

3. Feeding skills: There are two different stages in the growth process of river crabs: one is from the seedlings into the pond to mid-July, which is the shelf generation period. In one process, the shells need to be completed three times. The key to growing up. The second is after mid-August after entering the phenological maturity period, and then the weight gain and fattening period, after which it can be changed to feed trash fish, fresh grains and synthetic materials. Promote crab growth in the early stage, and strengthen fattening in the later stage.

4. Implement centralized fattening: In early September, after the crabs landed on the river crabs, began to focus on fattening.

5. Paddy fields are the best environment for adult crab fattening: synthetic materials, trash fish, snails, animal scraps, new corn and other grains are quickly fattened.

Fourth,Cultivate biological bait and feed the seedlings into the pool

Promoting growth in the early stage: There is no light in the middle and late stages of the paddy field, which is the reason why the crabs grow fast in the early stage but not in the later stage. To promote growth in the early stage, one is to cultivate plankton with agricultural fertilizer one week before the seedlings are placed. From the big eye into the pond, the seedlings are placed directly in the water. There are many organisms in the water. No feeding is required for 3-5 days. Sufficient amount, subject to a slight surplus.

Temporary farms can not feed for the first 2 days after cultivating plankton. When there are few organisms, feed at least 2-3 times a day. After the pool is divided, it is fed once a day, and the amount of input is slightly left.

Fifth,Promote growth first, control ripening in the middle, and fatten later

1. Promote the formation of racks in the early stage; in the early stage, use the fish mud and synthetic materials to soak and grind them.

2. Control maturity in the mid-term; generally by early August, when the crabs have basically completed 9-10 shells (accounting for 80%) and 90-110 per kilogram, the feeding should be stopped, otherwise the shell will be shed again, and most of them will show sexual maturity. .

3. Strengthen fattening before harvesting. Fattening should not be too early before wintering. Too early, such as high temperature in late autumn, is likely to cause shelling again and it is difficult to survive the winter without fattening time. Generally, the catch is in early October, and it should not be too late to start around September 15. However, it is necessary to check the fatness at any time. When the crab yellow is more obvious, the feeding should generally end in mid-August.