Crayfish (Procambarus clarkii), also known as Procambarus clarkii, red crayfish and freshwater crayfish, has a hard, dark red shell, a nearly black shell, a wedge-shaped stripe on the back of the abdomen, a body length of 5.7 ~1.8cm, three pairs of tentacles on the head and five pairs of feet on the chest, the first/kloc-. Crayfish has fast growth speed and strong adaptability, and the suitable water temperature is 10~30℃. The whole development process is divided into four stages: larva, juvenile shrimp, adult and adult shrimp. Larvae eat food brought by yolk or maternal respiratory water flow; Young shrimp live independently, mainly feeding on zooplankton, with a body length of1.0 ~ 3.0 cm; Adults are immature individuals, actively feeding on zooplankton and water worms, with a body length of more than 3.0 cm; Adult shrimps are parent shrimps and commercial shrimps with mature gonads.
2 crayfish rice field ecological breeding technology
2. 1 rice field facilities construction
Choose paddy fields with low terrain, good water retention, far away from pollution sources, abundant water sources and convenient irrigation and drainage to ensure that they are not flooded (20 19-21Japanese crayfish farmers in meishan town and Baitafan towns of Jinzhai county were affected by rainstorm and flood, and a large number of crayfish fled, resulting in economic losses/kloc. The area is 0.67~3.33 hm 2. Widening, heightening and strengthening the ridge, making it more than 0.8 m higher than the field surface, 5-6 m wide and 2-3 m wide at the top, and digging a rice field ring with a width of 3.5~4.0 m and a depth of1.0-0/.5 m along the inside of the ridge.
2.2 stocking preparation
2.2. 1 transplant aquatic plants. Planting aquatic plants accounts for about 30% of the paddy field area (50% of the area around the ditch), mainly Elodea nuttallii, Hyacinthus verticillata, Eichhornia crassipes, Water hyacinth, etc., and the suitable planting time is 1 1 month, and bio-organic fertilizer containing amino acids, humic acid and various trace elements is used.
2.2.2 Apply sufficient base fertilizer. Apply special fertilizer for biological rice. Seedlings are usually transplanted in the first and middle of June, and 750 kg/hm 2 special fertilizer for biological rice is applied as base fertilizer, 75 kg/hm 2 urea as tiller fertilizer and 75 kg/hm 2 potassium fertilizer as ear fertilizer. Avoid using ammonia water and ammonium bicarbonate. After rice harvest, the commercial straw decomposing agent 30 kg/hm 2 was applied, which could not only fertilize the field, but also be used as crayfish bait. In winter, 750 ~1500 kg/hm ~ 2 of bio-organic fertilizer or 60~75 bags/hm ~ 2 of dry chicken manure were applied, and they were spread flat in rice fields without opening bags.
2.2.3 Disinfection of rice fields. After the rice field transformation is completed, the ditch should be disinfected in the first 1 year, and the water should be disinfected with quicklime 1 800~2 250 kg/hm 2 to kill enemy organisms and pathogenic bacteria; When there are shrimps in the ditch, chlorine dioxide should be used for disinfection.
2.3 stocking
2.3. 1 shrimp fry selection. It is best to choose young shrimps cultivated in the surrounding rice fields or collected in ponds and ditches as shrimp seedlings, which require dark red or deep red color, luster, smooth body surface and no attachments; Individual size is even, appendages are complete, physical fitness is strong, and activity ability is strong.
2.3.2 shrimp transportation. For long-distance transportation of shrimp seedlings, high-quality young shrimps should be packed into plastic shrimp baskets, with the weight of each basket not exceeding 5 kg. After loading, 1 layer of wet aquatic plants should be placed on it, and the transportation time should not exceed 2 h; The running water truck is transported between 2~ 10 h; Nylon bags filled with water and oxygen can be transported over10 h.
2.3.3 Shrimp fry release. From May to June every year, the rice field is released with 40~60 young shrimps150,000 shrimps /hm 2 (equivalent to 3~4 cm); If young shrimps are released after the mid-season rice is harvested in September-1October, adult shrimps will be harvested from late April to May of the following year, and 225,000 young shrimps with the size of 2-3 cm will be replenished /hm 2. When throwing, the shrimp basket is repeatedly immersed in water for 2~3 times, each time 1~2 min, so that the shrimp seedlings can adapt to the water temperature, and then put in the enclosure ditch or field ditch.
2.4 scientific breeding
2.4. 1 rice planting. Generally, shrimp paddy fields only grow mid-season rice in one season, and dry-cultivate dry pipes, and choose water-saving varieties with small opening angle of leaves, resistance to pests and diseases, lodging resistance and strong fertilizer tolerance. Drainage of paddy fields from April to May; Transplanting in shallow water in early June, and planting with wide rows and dense plants, that is, the row spacing is 25~40 cm and the plant spacing is18 cm; Mid-season rice harvest from August to September. Scientifically plant rice, and do not spray or spray less pesticides all season, so as to reduce pesticide residues in rice and make rice taste better and have quality assurance. Crayfish have certain requirements for water quality. If the water quality is destroyed, crayfish will play an early warning role. The rice yield can reach 9.0~ 10.5 t/hm 2.
2.4.2 Feed feeding. After the shrimp larvae are released, a large number of zooplankton can be cultivated, which can provide good bait for the young shrimp. Increase feeding in July and August, such as vegetable cake, bean dregs, screw meat, mussel meat, lettuce leaves, ryegrass and so on. Try to make a reasonable combination of animal feed, plant feed and green feed to ensure balanced nutrition, and the feeding amount is 1% of the total weight of shrimp seedlings. Feed artificial feed 1 time every evening, and the feeding amount is 1%~4% of the weight of shrimp stored in rice fields.
2.5 Daily management
2.5. 1 molting management. Strengthen the management of crayfish during molting. It is strictly forbidden to interfere when a large number of crayfish molt, and feed high-quality and delicious feed immediately after molting to prevent killing each other.
2.5.2 Paddy field management. From July to September, the water level in rice fields should be controlled at about 20 cm, except for the drying period. After transplanting, the field should be sun-dried 15~20 d, which requires light sun-drying, and it is appropriate to sun the field until the foot does not sink and the field surface does not crack. After the completion of field drying, the original water level should be restored in time to avoid adverse effects caused by excessive density of crayfish in the ditch for a long time.
2.5.3 Water level management. After the rice is harvested, the water in the paddy field should be deepened slowly to avoid the rapid deterioration of water quality caused by the one-time flooding of rice straw and chicken manure. 10 ——1February water depth of farmland protection surface 10~20 cm shallow water level; /kloc-maintain a deep water level of 30~50 cm from October to February of the following year; Keep the shallow water level of 10~20 cm from March to April; Maintain a deep water level of 30~50 cm from April to May; Water level management shall be carried out from June to September according to the requirements of rice cultivation.
2.5.4 Water quality management and daily inspection. The most suitable pH value of water body is about 8, so it is necessary to use quicklime to adjust it regularly. The general dosage is 75.0~ 1 12.5 kg/hm 2, and it is sprinkled regularly every month. Establish a patrol system, adhere to the daily patrol of the field, and take countermeasures in time when abnormalities are found.
2.6 Prevention and elimination of diseases
The natural enemies of crayfish are carp, crucian carp, snakehead and catfish. Reptiles such as turtles and turtles; Land animals such as water rats, water snakes and wild cats; Heron, kingfisher and other poultry. Sprinkle quicklime1125 kg/hm ~ 2 before stocking, filter with 20-mesh gauze when entering the water, and set some colored strips and scarecrows at the edge of the field to scare and drive away water birds. For moss, quicklime was used to make slurry and sprinkled evenly while it was hot. The dosage of 1 m water depth was 300 kg/hm 2, and after 3 days, 75 kg/hm 2 of Helv Xiabao was used to cultivate algae to prevent moss from rebounding. Cyanobacteria were diluted with 500 mL of Jianshuibao to 100~200 times, and sprinkled evenly 1~2 times, with an interval of 10~ 15 d each time.
2.7 adult shrimp fishing
2.7. 1 wheel catching and releasing. The culture period of crayfish in rice field is about 60 d from larva to adult, and about 45 d from juvenile to adult. It can be caught after 30 d stocking. Crawfish can be caught by cage nets, hand-written nets, or by draining water. After the completion of the first 1 crop, according to the situation of young shrimps left in the rice field, 3~4 cm of young shrimps1.50,000 ~ 45,000 fish /hm 2 were replenished.
2.7.2 Reserve parent shrimps. In order to meet the demand of shrimp species for shrimp culture in rice fields, it is necessary to "catch large shrimps and keep small ones" in the early stage of adult shrimp fishing from August to September, and "catch small shrimps and keep large ones" in the later stage, that is, stop fishing until the size of shrimp caught falls below 0.4 kg/ shrimp, so as to keep enough parent shrimps for reproduction in the next year, with an average of not less than 225~300 kg/hm 2.