Techniques and methods of culturing swimming crab

Culture technology of swimming crab

pond condition

The pond area selected for northern aquaculture is generally 10-20 mu of medium and small ponds, and ponds near the sea area with sufficient water source, no pollution, rich resources of small miscellaneous fish, shrimp and shellfish and convenient water intake and drainage should be selected. Pool depth should be more than 5 meters. The bottom of the pond is better with mud and sand, and the bottom of the pond should be paved with sand about 15 cm.

preparations

The swimming crab is divided into three main steps:

The first step: pond finishing: pond finishing is mainly to remove excess sludge at the bottom of the pool, loosen the bottom of the pool, and also to maintain pond dikes, gates, canals and other supporting facilities.

Step 2: Set obstacles: In order to facilitate the rest and hiding of crab seedlings, when the pond is repaired, concrete pipes, tiles, bamboo tubes and other obstacles should be placed at the bottom of the pond.

The third step: water and breeding bait organisms: half a month after the pond can be opened to water, in order to prevent some harmful organisms from entering the pool, you can use 60 mesh sieve silk net to filter seawater, the depth of the pool water is generally maintained at about 80 cm, after the pond water, fertilizer should be applied to cultivate bait organisms, generally N fertilizer is 1.5kg/mu, P fertilizer is 0.3kg/mu, and the transparency of the pool water should be maintained at about 30 cm.

crab seedling stocking

1. Source and selection: The source of crab seedlings mainly includes fishing in natural sea areas and artificial cultivation. The specifications of seedlings are generally 80/kg. The crab seedlings are required to be neat, healthy, complete appendages, strong vitality, and soft shell rate is less than 10%.

2. Stocking time: We generally stock in late May-mid-June.

3. Water quality requirements: water temperature should be above 18℃, daily temperature difference should be less than 8℃, salinity should be 18-32, pH should be 7.8~8.6, ammonia nitrogen content should be less than 1 mg/L water, dissolved oxygen should be greater than 5 mg/L water, transparency should be maintained at 30~40 cm.

4. stocking density: generally 80-100/kg crab seedlings, stocking density should be controlled at 1000 - 1500/mu.

Daily management of swimming crabs

1. Water quality management: in July, water should be changed every 2-3 days; in August and September, water should be changed every 1-2 days; in October, water should be changed every 4-5 days; the specific water change amount and water change interval should be changed according to environmental factors such as weather and water temperature.

2. Feeding: Portunus trituberculatus is omnivorous, it takes fresh low-value fish, shrimp, shellfish, crab and so on as the main bait. Daily feeding bait amount according to the size of crabs and different, breeding early stage generally according to the crab's total weight of about 8% feeding, medium for 12%, late for 5%; when the autumn water temperature dropped to 10~15℃, the daily feeding amount should be 3% of the total weight, according to the morning and evening feeding 1 time, less in the morning, more in the evening feeding principle, the average water temperature of the day below 10℃, do not feed bait.

3. Pool patrol management:

Patrol the pond once in the morning and evening. During the patrol, carefully observe the feeding and activity of swimming crabs, pay attention to the change of pool water, check the residual bait in the pond, and adjust the feeding amount and water change amount in time. Pay attention to weather changes at any time and prepare for flood control and typhoon prevention. Always check whether the blocking net and dam of the gate are damaged or not. If any problems are found, repair them as soon as possible.

harvest operations

The harvest time of swimming crab should be in late autumn, when the water temperature drops below 15℃, swimming crab no longer continue to gain weight should be harvested in time. Timely catch of swimming crab is the key to high quality, high efficiency and high yield. The fishing time should be determined according to whether the crab enters the crab period, the selling price and the weather conditions. Generally, it is better to arrange the fishing time in December, and it should not be caught on rainy days. Crabs can be taken out of the pool at night with crab cages or fishing nets. When a large number of pond should be fixed in the gate cage bag, the use of low tide water, so that swimming crabs with the flow into the cage bag, when the pond water discharged to the lowest point, can be used iron rake slowly along the bottom of the pond. When encountering crab body, carefully stir it up and fish it into basket or bucket with small copying net. The swimming crab should be tied with rubber band to prevent biting each other or escaping in the basket or bucket.

Efficient polyculture of swimming crab

Controllable ecological polyculture technology is an effective way to improve the economic benefits of aquaculture ponds. Reducing aquaculture costs, reducing aquaculture risks and improving aquaculture benefits are the goals that aquaculture personnel have been pursuing. The author summarized several key points in the process of pond polyculture of swimming crab and white shrimp as follows:

1. Fertility is important for cleaning ponds. Disinfect 50 cm of pond water with bleach, kill copepods, remove harmful organisms, etc. Urea or fermentation disinfection of chickens, pigs, so that the color was brown or yellow-green.

Portunus 2. Release of shuttle crab seedlings and shrimp seedlings. Shuttle crab seedlings are generally put in the middle and late May. It is advisable to select the third stage young crabs bred in soil ponds, and put 1 kg per mu. Pay attention to the seedlings with uniform specifications and strong physique when throwing seedlings. The young white shrimps are self-propagated by spawning shrimps. The local spawning shrimps are put into the late June without damage, sensitive to external stimuli and active in swimming. The young white shrimps are put into the late June, and the young white shrimps sprout completely. There are few diseases, which is beneficial to the growth of shrimps and crabs and convenient for production and management.

3. Pond water management to prevent "algae fall" and hypoxia. After changing water with algae in pond, it is most important to stabilize water and detoxify. Conditional pond, it is recommended to change the water every 5-7 days, after water to use disinfectant to disinfect the whole pool, bacteria into the bottom quality is the key to successful breeding, breeding personnel should regularly improve the bottom of the pool, should change the bottom once a week, to prevent hypoxia, reduce the incidence. Always pay attention to sudden changes in weather and prevent "falling algae". When the water color is too thick and the transparency is lower than 30 cm, the upper layer of the pool water shall be drained, fresh seawater shall be added to inhibit the propagation of algae, chlorine dioxide and dibromohydantoin may also be used to disinfect the water body, and microbial agents shall be applied to restore the water color; daily inspection and recording shall be strengthened, and the aerator shall be started in time, especially in the evening and at night, to increase the dissolved oxygen of the pool water through the aerator, so as to maintain a good water color.

4. Feeding of bait. To insist on a small number of meals, frequent inspection, pay attention to fresh food palatability, to improve the conversion rate of bait, reduce feces, ensure that shrimp, crab eat not waste, breeding early can put some EM bacteria and other biological agents to decompose ammonia nitrogen, improve the bottom of the pond, prevent pond hypoxia poisoning.

5. Remove male crabs in time. In order to reduce the breeding cost and improve the breeding income, it is suggested that the breeding personnel catch male crabs from early July to the end of August, which not only improves the breeding density of the pond, but also saves the bait cost. Moreover, in the mating season of swimming crabs, if there are too many male crabs, the swimming crabs will kill each other in the pond, which will affect the economic benefits of the farmers.

6. Do a good job of swimming crab fattening in autumn and winter. During the fattening period, the thickness and hardness of the crab shell can be increased by supplementing organic calcium, so as to increase the weight. In the middle and late stages of cultivation, more low-value shellfish can be thrown to promote the development of crab gonads and the accumulation of nutrients.

7. Rotational catch of white shrimps over 5 cm. During the cultivation period, according to the market conditions, nets such as cages can be used to catch white shrimps in a planned way, keep small catch large, sell fresh, control the density of white shrimps in the pond, prevent hypoxia, and withdraw funds in time.

8. Disease control runs through the whole process of breeding. Adhering to the principle of "prevention first, prevention combined" and maintaining a good pond water quality environment are the foundation for successful breeding.