How to avoid the misunderstanding of freshwater crayfish culture and obtain higher economic benefits in 2018?

In the process of freshwater crayfish culture, it is necessary to rationally analyze its living habits, the source of species, the setting of culture environment, the reasonable collocation of bait, the prevention and control of diseases and the scientific prediction of yield, so as to formulate the corresponding culture plan. in order to reduce the probability of entering the misunderstanding of culture and obtain higher economic benefits.

In recent years, with the increasing market demand, the "breeding fever" of freshwater crayfish is heating up year by year, and many aquaculturists focus on crayfish culture. However, many farmers do not fully master the correct culture technology, thus ignoring the normal management of lobster breeding, water quality environment, bait feeding, disease control and so on. Finally, it is difficult to improve the economic benefit of breeding. Through visiting and investigation, it is considered that there are mainly six misunderstandings in freshwater crayfish culture:

First, lack of understanding of crayfish's living habits

From the first autumn (September to October) when the crayfish reached sexual maturity, the crayfish began to mate, dig holes and hold seeds. The growth, development and overwintering process of the shrimp larvae were attached to the abdomen of the mother, and separated from the mother and lived independently when the larvae reached more than 2~3cm in the next spring (February to March). After more than 2 to 3 months of growth, it is the adult shrimp holding eggs. Therefore, the scientific release time of crayfish seedlings and species is in spring and autumn. Spring investment can choose to put shrimp seedlings into the pond at the end of March and early April, and autumn should plant shrimp into the pond at the end of September and early October. After self-rest and adaptation, let it reproduce naturally in the pond, which can not only provide seedlings for its own pond mouth, but also sell some of them. Because crayfish have the habit of digging holes and running away, crayfish ponds should be built with nets, wooden stakes, thick plastic skins or other sheets to prevent escape. Crayfish generally hole in 30~40cm, some up to about 1 meter, so the width of the ridge had better be more than 3 meters, to prevent crayfish hole escape.

2. On the varieties of freshwater crayfish

At present, the scientific name of freshwater crayfish, Procambarus clarkii, belongs to crustacea, Decapoda, Crayfish family, Procambarus, native to northern Mexico and southern United States. Japan was introduced into Nanjing through Japan shortly after it was introduced from the United States at the beginning of the 20th century. Now it has been distributed in more than 20 provinces and cities, and has become one of the important resources of freshwater shrimp in China. At present, the crayfish cultured in the middle and lower reaches of the Yangtze River, such as Jiangsu, Anhui and Hubei, are all of one species, and there is also a "hybrid" crayfish species, which is the research object of the fishery professional department and is basically in the experimental stage. The technical level still needs to be mature and improved. There is a difference between artificially domesticated seedlings and natural breeding seedlings. Artificial breeding is difficult to popularize this technical variety on a large scale because of the high cost and the high yield and low price of wild seedlings in ditches, ponds, rivers and lakes. Of course, the survival rate of artificially cultivated seedlings is very high, up to about 85%, while wild seedlings are generally only about 70%, and there are also limitations of the geographical location of the water body. Generally speaking, the selection and release of crayfish seedlings in Tangkou culture is only one of the important links in culture, and what is more important is what kind of effective scientific management methods should be adopted in daily culture. If the management can reach a higher level, the probability of success in culture is higher, otherwise it will fail.

Third, the production of freshwater crayfish is too idealized.

The production of crayfish culture is closely related to the release of shrimp seedlings, the control of water environment, the combination of meat and meat in feed, the management of daily scientific system, and the timely pre-control of common diseases. It is generally selected that the shrimp fry with a size of 130,150 / kg per mu in April and May is about 50kg / kg. After about 70 days of rapid growth, the method of selling big and raising small can be adopted in June until the end of October. A total of 150 million 180 kilograms of crayfish can be caught in Tangkou per mu. According to the culture level, the average size is 20 million 30 crayfish / kg. Culture technology, pond conditions can slightly increase the number of shrimp seedlings, increase feeding, the yield per mu will be increased to a certain extent, as for those who unrealistically exaggerate and advocate a higher yield, there is no scientific basis, at most, it is a case.

Fourth, the bad environment control of aquaculture water is not enough.

Crayfish usually have a strong ability to adapt to the aquaculture water environment, causing some people to misunderstand that crayfish like to live in black and smelly water bodies, and the quality of the water body is not important. The truth is that crayfish that live in dirty water are dirty and black, with a hard shell and a small head, which makes it difficult to produce an appetite. A correct understanding should be that fresh water quality, abundant water plants, high dissolved oxygen and no pollution are the key to raising crayfish. The lack of aquatic plants in the water body, first, the lack of dissolved oxygen, second, when the crayfish shelling, there is no good cover enemy areas, they will be attacked by the same kind or other carnivorous aquatic animals, resulting in animal emergency response, many crayfish will appear slow growth phenomenon, the occurrence of "old shrimp" will be very obvious.

Fifth, the bait feeding is not in place

The intensive cultivation of crayfish in Tangkou must increase the intensity of bait feeding, which can reduce the crayfish to kill each other because of lack of bait and improve the survival rate of crayfish. In the selection of feed varieties, we should pay attention to the scientific and reasonable collocation of crude and refined meat and meat, and adopt the meat-meat-meat method, that is, 70% of animal feed in the early and later stages, 70% of plant feed in the middle stage, and no input of poultry offal and other animal materials as far as possible when conditions permit. Daily animal feed can choose unspoiled small wild miscellaneous fish, snail meat, etc., while plant feed is mainly composed of aquatic plants such as corn, bean cake, pumpkin and Elocha. The amount of bait feeding should be adjusted in time according to the timely temperature, cloudy and sunny changes, crayfish activities, appetite and existing pond storage, etc. Generally, the feeding proportion is 3%-5% of the total weight of shrimp stored in the pond, and it is appropriate to eat it 2-3 hours after feeding. It is necessary to closely observe and strictly prevent the residual bait from causing pollution to the pond water.

Sixth, do not pay enough attention to the prevention and treatment of crayfish diseases.

Because the crayfish has strong resistance to disease, it generally does not get sick, but when it is artificially concentrated, many uncertain factors are easy to cause disease. For example, a few years ago, nearly a thousand mu of white spot disease appeared at the mouth of crayfish culture ponds in villages and towns along the Huaihe River in Xuyi County, and many farmers ended up with only a pool of empty water. To investigate the reason, crayfish culture must do a good job of disease prevention and control. First, start to clean and disinfect the ponds and sprinkle the whole pond with 80,160 kilograms of quicklime per mu to thoroughly kill all kinds of enemies and pathogenic microorganisms. Second, in the process of breeding from May to September, sprinkling quicklime or chlorine preparation in the whole pool every 10 to 15 days can effectively kill a variety of pathogens. Third, when the high temperature is from July to August, the water level should be raised to about 1.2 meters to reduce the bad environment temperature of the culture water body, so that the crayfish can maintain a certain growth rate in the suitable ecological environment. Fourth, in the middle and later stages of culture, the excessive organic matter accumulated in the pond could not be fully oxidized and decomposed due to hypoxia, and anaerobic decomposition replaced oxidative decomposition, resulting in a large number of harmful substances such as ammonia nitrogen, hydrogen sulfide, nitrite and so on. Crayfish chronic poisoning, a large number of pathogens breed, resulting in crayfish illness or death. At this time, biological agents and EM bacteria should be used to regulate the water quality and improve the sediment, and the production of pathogenic microorganisms should be inhibited by biological antagonism so as to create a good ecological environment. Fifth, do a good job in daily inspection of Tangkou. When abnormal phenomena occur in crayfish, it is necessary to quickly check and diagnose, find out whether there is a problem in the bad water environment or shrimp body disease, prescribe the right medicine to the case, and take remedial measures in time. At the same time, the dead shrimp should be fished out of the pond water and buried in the pond to cut off the spread of the disease again.