The continuous cropping of shrimp and rice should choose paddy fields with sufficient water, convenient irrigation and drainage, strong water retention, dry weather without flooding, good ecological environment, no pollution sources around, fertile soil and natural sediment structure. Generally speaking, low lake field, cold immersion field and winter immersion field are more suitable. The area is not limited, but it is not cost-effective if it is too small. It is best to take 50 mu-100 mu as a breeding unit. For bases with large scale and high requirements for output and benefit, we should also consider convenient transportation and guaranteed power supply.
2. Environment
Including the excavation of ring ditches and furrows, the widening, heightening and strengthening of ridges, the control of water quality and water level, and the planting of aquatic plants.
(1) Excavation: an annular shrimp culture ditch is dug along the inside of the rice field ridge, with a width of 2m and a depth of1m.. The annular shrimp culture ditch is 2m away from the ridge, and the corner is preferably arc-shaped. A unit with an area of 100 mu needs to dig a "cross" or "I" shaped ridge ditch in the middle of the ridge. The width of the trench is 0.5 ~ 1 m and the depth is 0.5 m. The area of annular ditch and intertidal ditch accounts for 5% ~ 10% of paddy field area.
(2) building a ridge. Widen, heighten and reinforce the surrounding ridge with excavated soil. The top of the ridge is 2-3 meters wide and at least 0.8 meters higher than the field. The ridge should be tamped to prevent water seepage or collapse.
(3) planting grass. Planting aquatic plants can not only provide high-quality bait for crayfish, but also provide a good environment for its habitat and molting growth, which is one of the key measures for the success of crayfish culture. Aquatic plants refer to submerged plants, and water hyacinths and water peanuts can also be planted.
(4) Control water quality and water level. The water quality should meet the requirements of healthy farming. Freshwater crayfish are very sensitive to heavy metals and some pesticides such as trichlorfon and pyrethroids, which should be paid attention to. The water level should generally be kept 30-60 cm higher than the field surface; The temperature drops rapidly in autumn and winter, so it is advisable to raise the water level to keep warm; In spring, the temperature rises rapidly and the sunshine is strong. It is necessary to lower the water level and raise the water temperature. In summer, the temperature is too high, and the water level should be deep, so as to achieve the purpose of proper cooling.
3, pest control
Continuous cropping of shrimp and rice threatens the survival of crayfish. Water centipede, frog, water snake, eel, loach, carnivorous fish (such as catfish, loach and mullet) and water rat are all natural enemies of crayfish. Therefore, crayfish must be thoroughly removed with drugs (such as quicklime) before stocking, and it must not be careless. The water inlet should be filtered with 20-40 mesh gauze, and the water outlet should be surrounded with dense mesh net to prevent the enemy from invading. Patrol frequently at ordinary times to remove enemies and pests in the field in time. Conditional can set up some scarecrows and colored strips on the edge of the field to scare away waterfowl.
4. Seed sowing
Adhere to early release and full release, and pay attention to quality. In the rice fields where shrimp and rice are continuously cropped, young shrimps should be put in September 9- 10/0 or parent shrimps should be put in July-August (a temporary parent shrimp culture pond can be set up near the rice fields, preferably connected with the shrimp rice fields, and the middle rice should be irrigated and put into the rice fields in time after harvest). Dosage: after mid-season rice harvest from September to June every year, 65438+1October, crayfish and young shrimps with the number of 1-20000/cm or more are put into irrigated rice fields, or parent shrimps are put into annular ditches for mid-season rice harvest from July to August every year, and put into rice fields or temporary breeding ponds nearby. It is best to catch the parent shrimp directly from the nearby aquaculture pond or natural waters, and the time out of water is generally no more than 2 hours; It is necessary to adhere to the quality standards of seed selection, and try to choose male and female shrimps with complete appendages, strong physique, no disease or injury, smooth body, no attachments, strong mobility and individual weight of more than 30 grams as parent shrimps, with the male-female ratio controlled at 2-3: 1. According to the above dosage and scientific management, each acre of rice field can produce 200-300 Jin of commercial shrimp, and the net profit per acre will increase by 600- 1000 yuan.
5. Escape prevention
Crawfish crawls at the bottom and has a strong ability to swim against the current. Pay attention to escape. The water inlet and outlet of shrimp paddy field should be fortified with escape facilities, the water inlet should be filtered with 20~40 mesh screen, and the water outlet should be surrounded with dense mesh net to prevent freshwater crayfish from escaping by water; The ridge around the paddy field should be surrounded by a 70 cm wide dense mesh net or asbestos tile, with the lower end of the net buried in the soil for 20 cm, and the soil above it is divided into 90 degrees and inclined inward. It is more economical to use asbestos shingles as escape walls. The cost per meter is 2.5 yuan, which can be operated for 3~5 years with good results. At ordinary times, always check whether there is any leakage in the import and export and closed nets or asbestos tiles (rats can bite through the nets) to prevent shrimps from escaping.
Step 6 feed
Correct feeding and fertilization are important measures to improve aquaculture yield. Lobster is omnivorous, and the commonly used feeds are snails, clams, wild fish and shrimp, livestock and poultry leftovers, water, land grass, vegetables, corn, grains, rice bran, wheat bran, bean dregs, cake and so on. Aquaculture should be based on aquatic plants and farmyard manure, with appropriate agricultural and sideline products such as bean dregs, rice bran, wheat bran and cake meal and special feed for crayfish. Feeding should be "four fixed", that is, "fixed time, fixed point, qualitative and quantitative" Specifically, animal feed is the main feed in the early stage, aquatic plants, farm manure and agricultural and sideline products are the main feed in the middle stage, and agricultural and sideline products and artificial compound feed are the main feed in the later stage. Stick to 1 ~ 2 times a day, feed it once in the morning and once in the evening, and the daily feeding amount should be controlled between 1% ~ 3% of the total number of stored shrimps (to the extent that the bait fed on the same day is eaten within 3-4 hours). You can put more snails and clams where conditions permit.
7. Disease prevention
Crayfish diseases are less under the continuous cropping mode of shrimp and rice. At present, it is found that there are two main diseases that bring losses to crayfish culture.
1, virus disease. It is caused by virus, which shows weakness of diseased shrimp claws, hepatopancreas enlargement and dark color. Fasting, intestinal congestion, color segmentation Control method (1): spray 0.3~0.5mg/L povidone iodine or quaternary ammonium salt complex iodine twice, each time with an interval of 1~2 days; (2) splash water with100 ~150g chlorine dioxide per mu. Adding yeast immune polysaccharide to feed can play a preventive role.
2, ciliary disease. It is caused by the attachment of ciliates, which shows that a thick layer of "hair" is formed on the body surface, appendages and gills of adult shrimp, young shrimp, young shrimp and fertilized eggs. Control method (1): 0.3~0.5mg/L quaternary ammonium salt is used to spray iodine on the whole field; (2) Use fibrinogen or zinc sulfate as instructed. In addition, feeding crayfish with special artificial feed for molting can promote crayfish molting and make them shed their old shells with ciliates.
8. fishing; catch fish
Long-term fishing, catching big fish and raising small fish is a very important measure to reduce costs and increase production. From the beginning of April every year, crayfish cages and ground cages must be used to catch and sell crayfish that meet the commodity specifications (those that fail to meet the specifications will continue to be cultivated in rice fields). This can not only catch large-sized crayfish in time and sell them at a good price, but also reduce the density of crayfish in rice fields, promote the rapid growth of small-sized crayfish, and improve the yield and efficiency. Fishing method: put the shrimp cage and the ground cage net (mesh size is about 2 cm) in the shrimp ditch of the rice field or in the rice field, and get out of the cage every morning to collect the shrimp. Shrimp cages and ground cages move regularly to facilitate shrimp catching. If possible, bait can be set in the cage to lure crayfish into the net. At the end of May, it can be caught in the dry field in the night before mid-season rice transplanting.