Crawfish crayfish formerly known as P. clarkii, commonly known as "lobster", belongs to the crustacea, soft armor class, Decapoda, crawfish pie, Procambarus. Crawfish crayfish native to North America, the 20th century, the 20th century by the Japanese moved into their own culture, and later moved to stocking in Nanjing, China. Because of its wide adaptability, strong breeding ability, and rapid population development, it has expanded to many provinces and cities in China. Some lakes and regions have developed into dominant species. Take Jiangsu as an example, the output in the early 1990s reached 60,000. Ton. In recent years, Crawfish crayfish has attracted a lot of fish due to its delicious taste, rich nutrition, and low prices, as well as the extensive use of astaxanthin and chitin extracted from shrimp shells in the fields of food, medicine, health care, and papermaking. As a result, the natural resources of the crayfish are dwindling. For this reason, artificial breeding of crayfish has been carried out in many places. However, due to the serious phenomenon of mutual sustenance between the individual crayfish crayfish, shrimps, especially juvenile clams and fresh clams, are easily eaten. Therefore, the production has not been high. In this case, we conducted a polyculture test using the crayfish crayfish and the habits of cockroaches and squid and achieved good results. This new breeding mode has a very high promotion value and can provide a new bright spot for the currently unimpressive freshwater aquaculture industry. We now summarize our experience and techniques for reference.
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1 Preliminary preparation
1.1 Pond Conditions and Water Quality Requirements Ponds are best chosen where there is adequate water, wide ground, and slightly inclined terrain. There are no mountains or buildings around it, ensuring good ventilation and contributing to the convection of the pond water. The area of ​​the shrimp pond is not limited, but from the perspective of easy management and fishing, it is better to use 3 to 5 mu and a rectangle, and the water depth is 0.7 to 1.5 m. It should not be too deep. Ikei should have a certain slope, which is conducive to the growth of aquatic plants, dissolved oxygen, and the ingestion and growth of fish and shrimp. Under proper temperature conditions, shallow water culture is preferred. Fresh water, no pollution, dissolved oxygen in water more than 5 mg/L, pH value of 7.0 to 8.0. Dividing drainage and irrigation is conducive to the regulation of water quality and the prevention and treatment of diseases. The river water quality also requires good, fresh and pollution-free.
1.2 Cleaning and Disinfecting Ponds To remove excessive silt in the tank and leave at most 10 to 20 cm, the cleared sludge is used to repair the reinforcement tanks. Before exposure, dry ponds are exposed for 15 to 30 days. It is advisable to use hard and cracked joints at the bottom of the pool. In addition to the strong dyke around the pond, the pond can also be enclosed with simple materials such as plastic film or plastic nets to prevent the escape of shrimp or the encroachment of enemies such as snakes and rats. Thoroughly drained ponds can be sun-disinfected; ponds with accumulated water can be treated with drugs.
After the pond has been used for one or more years, silt in the pond, excrement of fish and shrimp, residual bait, animal carcasses, plant debris, etc. are deposited at the bottom of the pool, causing pollution, which is one of the major causes of pond aging and low yield. When these organisms reach the cultivation stage of the following year, they will decompose a lot because of the high water temperature, consume dissolved oxygen in the water, produce various toxic substances, and affect the growth of fish and shrimp or cause diseases. Therefore, it must be thoroughly cleaned before stocking.
1.3 Planting aquatic weed Crawfish prefer to live in lush areas of aquatic plants, so that it has more food organisms (especially the seedling stage), and there is a hidden environment for shelling and growth. Therefore, before the stocking, the shrimp ponds around the pond will be at the bottom of the beach. A certain number of plants are planted in the shallow water zone. The best choice is water, seaweed or water spinach. It can be planted by spraying seedlings or transplanting seedlings. Aquatic grass covers 10 to 15% of the pond area. In the nursery transplanting disinfection with 1010-6 bleach solution.
1.4 Water inlets and fertilizers The water inlets need to be equipped with water filters. Generally, 60 to 80 mesh sieves are used to grow the tubes. They can grow 1.5 to 2 m in diameter, and are cylindrical. When entering the water, they are prevented from being mixed with harmful organisms. In the first 10 days of the fish pond, the fish was fed with 50 cm of water and then fed with water to cultivate food organisms. Fertilizer can be fermented chicken, pig manure and weeds and other organic fertilizer, mu 200 ~ 250 kg (newly excavated shrimp pond fertilizer can be an appropriate amount of increase). After the first fertilization, according to changes in water color, pH value, and transparency, the fertilizer is applied to topdressing the primary fertilizer so that the pH of the pool water is maintained at 7.0 to 8.0, and the incubation water color is dark brown or light green, and the transparency is 25 to 30 cm.
1.5 Set the nets to set 1033 meshless summer flower nets in the middle of the pond and fix them with a bamboo frame. Set it in the shape of a truss at 20-40 cm below the water surface, with a gradient of 15-20 degrees to facilitate the crawling of the crawfish up and down. The length of each grid is 3 to 4 m, and the specific length is determined by the pool. Generally, there are 2 rows of ponds with an area of ​​about 2000 m2.
2 Replacing seedlings Currently, the problem of artificial seedlings of crayfish has not been solved. However, the problem of seeding can be solved by using wild shrimps or wild juveniles. For the amount of eggs held shrimp, generally 40 ~ 50 kg/667 m2, put in March and April. When the amount of wild juveniles in May and June is relatively large and the price is cheap, they can be purchased in large quantities, and some young prawns can be put in. If you can't buy egg prawns, you can put all the prawns (3 to 4 cm in length) and put them in. The amount is 100-120 kg/667 m2. If the juvenile size is larger (more than 5 cm), the amount can be increased appropriately. In the breeding process, we use shrimp as the main ingredient. The amount of earthworm and catfish should not be too large. Generally, the individual (200-250 g/tail) of the fry is generally selected, and each is fed at a quantity of 500 pigs per 667 m2.
3 daily management
3.1 Feeding
3.1.1 Time and place of feeding Since the amount of shrimp feeding is relatively large, it is necessary to cast enough bait to avoid self-mutilation due to lack of bait. Usually every day is divided into morning and evening. It is best to put in the sun before and after the sunset, and mainly in the evening (70% to 80% of the whole day). The method of feeding is “settling four timesâ€, that is, timing, fixed-point, qualitative, and quantitative; watching the season, watching the weather, watching the water quality, watching the crawfish feeding conditions, and determining the increase or decrease in the amount of bait. Mainly in the shore and shallow water more uniform feeding, the morning feeding should be far away from the beach, evening feeding should be closer. It is also possible to add a bait station around the shrimp pond in order to observe the shrimp feeding situation.
3.1.2 The composition and feeding amount of bait are different in each stage. In the larvae with a body length of 1.5 to 3 cm, the crushed fine bait (such as fish larvae and other animal baits are made into small granules) has a small daily feeding amount. Shrimp weight 7% ~ 8%; 5 ~ 8 cm in the shrimp stage of the bait to be processed into a certain size (such as wild fish, livestock and poultry waste cut into large chunks of Beans, hawthorn shaved wire) and then fed, Japan The amount of feed is about 5% of the shrimp body weight; the food of the shrimp stage can be slightly thicker, and the daily feeding amount is generally 2% to 3% of the shrimp body weight. In the case of juvenile shrimp, animal-based diets should be used as the main ingredient and vegetable diets should be supplemented; in the medium term, it should be gradually turned to the feeding of plant-based diets, and should be supplemented with animal baits; The middle green." It is usually appropriate to eat within 2 to 3 hours after feeding, and the specific amount of feed should be based on the weather, crayfish eating and drinking conditions, water temperature, water quality, and other conditions, flexible control, timely and reasonable adjustments.
3.2 Water quality management During the rearing process, the dissolved oxygen in the pool is kept at 5 mg/L or more, the transparency is about 30 cm, and the pH is 7-8. Aerators should be opened in due course, open at noon on sunny days, and open in the middle of a rainy night. If signs of floating head are found, they must be opened as soon as possible; if necessary, new water must be added. Normally change the water every half a month, Wang Shiwang long season 2 to 3 times a week, or even every day to change the water once in the evening. In addition, depending on the water quality, every 15 days, about 15 kg/667 m2 of quicklime is used as a water solution. Take a patrol once a day in the morning and evening, and take appropriate measures in case of abnormalities.
3.3 Disease Prevention and Control
3.3.1 Disease Prevention The disease resistance of crawfish is strong, and no explosive or epidemic disease has been found since its introduction. However, in the artificial high-density culture, the disease prevention and treatment work cannot be taken lightly. Prevention and control work should be based on prevention, the good feed off, good water management, seedlings before the next pond, can be used 1% ~ 2% NaCl solution dip 10 ~ 15 min, to prevent the pathogens into the pool.
3.3.2 Prevention and cure of several common diseases 1 Hemorrhagic disease: Septicemia caused by Aeromonas salmon. The disease is ferocious and the incidence rate is high. Shrimp body surface covered with blood spots of different sizes, especially appendages and abdomen, anal swelling, once infected, will soon die. During the onset of the disease, it was found that the diseased shrimp was isolated in time, and the water in the shrimp pond was disinfected. The pool with a depth of 1 m was splashed with quicklime at a rate of 25 to 20 kg/667m2, and it was best to splash it once a month. Oral drugs were fed with ciprofloxacin hydrochloride at a rate of 1.25 to 1.5 g/kg of bait and fed for 5 days.
2 Saprolegnia: The pathogen is the aquatic mold. The crawfish are susceptible to the disease during fishing, transportation or tank transportation. The water quality is deteriorating and the crawfish's constitution is also vulnerable to the disease. The initial symptoms are not obvious. When the symptoms are obvious, the hyphae have invaded the epidermal muscles and grow out of the cotton-like hyphae to form a visible white hair on the body surface. Shrimp body weight loss, activity irritability, reduced food intake, leading to serious death. After the onset of disease, 1% to 2% NaCl solution was used to dip the diseased shrimp for a long time. At the same time, every 100 kg of feed plus glucazozol 50 g made bait and fed 5 to 7 days, a better effect.
3 Polydenosomiasis: It is caused by parasites parasitic on the shells of shrimps. Symptoms are that the shrimps have more dirt on the surface and their ability to feed and move is reduced, and severe cases die before dawn. The main prevention and control measures are the management of good water quality. When the disease occurs, use lime to spray 25 to 30 kg/667m2 of Quanchipi to adjust the water quality. Shrimp with 0.5 ~ 110-6 of benzalkonium with 5 ~ 1010-6 potassium permanganate dipping, the effect is better.
4 black shank disease: the disease caused by the Fusarium, the main damage to adult shrimp. Shrimp appeared pale yellow or orange patches on the ankles, body surface, and appendages. As the disease progresses, the patches turn light brown, and when severe, the moles are dark and ulcerated, and sometimes the appendage plaques also ulcerate. Finally, the diseased shrimp die. Shrimp body susceptible to infection after injury. Chlorine dioxide 0.310-6 concentration can be used to disinfect the whole pool and quickly change the water.
In the polyculture test, we mainly used crayfish as the main ingredient. The density of puffer and squid stocking was small. During the whole breeding process, serious water fish disease did not occur due to satisfactory water quality control.
4 Crawfish clams can be trapped in shrimp cages from mid-August, leaving them large and small until mid-October. The advantage is that it avoids centralized listing, and it can gradually reduce the density of shrimp ponds, which is conducive to accelerated growth. The remaining crawfish can be fished together with squid and squid at the end of the year.
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