Get rid of the eight misunderstandings of soilless Culture of Monopterus Albus

The original article was published in Scientific Fish farming, No. 11, 2009.

Ricefield eel is a favorite delicacy, which has been kept at a high price in the market. Soilless culture has the advantages of low cost, easy to catch Monopterus Albus, high culture density, high yield and high benefit, so it is suitable for indoor and outdoor culture and has a good development prospect, but some one-sided and even misunderstandings in production are widely spread. there are mainly misunderstandings in the following eight aspects, which restrict the healthy development of Monopterus Albus breeding industry. First, using aquatic plants as fish nests after long-term natural selection, Monopterus Albus has formed the habit of living in caves, and its significance is to avoid enemy damage and to avoid the attack of high temperature and cold. In production, the root system with dense water plants is generally used to make fish nests. However, using only aquatic plants as fish nests is easy to make eels gather and entangle, resulting in excessive local density, and Monopterus Albus perched in aquatic plants is prone to cold disease due to the great change of water temperature. The combination of waste tires and black plastic bags provides fish nests for soilless culture of Monopterus Albus. The environmental temperature is stable, which is conducive to the free entry and exit of Monopterus Albus, and overcomes the shortcomings of inconvenience of fish nests such as PVC tube, tile, stone, bamboo tube and so on.

At present, soilless culture of Monopterus Albus imitates the practice of cage culture, that is, it is concentrated from the end of June to the beginning of July, resulting in higher seedling price and shorter culture season (about 3 months). In cage culture, Monopterus Albus lives in water grass layer and must be planted after the water temperature is stable (that is, from the end of June to early July). However, in cement pond soilless culture, Monopterus Albus lives in underwater tires, and the water temperature is relatively stable. Seedlings can be released before and after the Qingming Festival.

At present, the artificial breeding technology of Monopterus Albus in China has not yet reached the level of mass production and supply of commercial breeding. many farmers buy wild eel seedlings from the market, mostly with salt water, potassium permanganate, iodine preparations and so on. promote a large number of rice field eel mucus to fall off, affecting its survival rate. Yellow eel scale, Gill, fin degeneration, the outer barrier is mucus and skin, mucus contains a lot of lysozyme, has a strong resistance to bacterial infectious diseases. Therefore, it is best to choose drugs with little irritation to Monopterus Albus mucus, such as gentamicin, chlortetracycline and Duoyishan No. 1, in order to improve the survival rate of Monopterus Albus and promote the feeding of Monopterus Albus in advance.

Fourth, size can not be mixed culture in production, many farmers think that rice field eel size can not be mixed culture, carefully separate the size of rice field eel when screening, culture for a period of time due to inconsistent growth of rice field eel will have to separate ponds, both laborious and because of the operation back and forth affect the survival rate of rice field eel. It is true that Monopterus Albus preys on small eels, but it is not as serious as the relevant data. Whether hungry or not, the phenomenon of preying on Monopterus Albus occurs only when the individual difference reaches a certain degree. According to the study, the frequency of wild young eel swallowing juvenile eel is 2.54%, and the minimum individual length is 192 mm; the frequency of adult eel swallowing juvenile and young eel is 11.43% [1]. It can be seen that the frequency of rice field eel preying on small eel increases with the increase of individual difference. When the body weight ratio reaches 25:1, the ricefield eel will kill each other, and the big eel does not affect the growth of the small eel [2]. Therefore, it is only necessary to pick out the larger ricefield eels during screening, and there is no need to breed them in many groups according to their size.

Monopterus Albus is the only fish that can drown in the deep water. Due to the serious degeneration of its gills, Monopterus Albus mainly breathes air through the mouth and nostrils, and its oxygen intake accounts for about 3% of the oxygen needed by Monopterus Albus. Therefore, the water in the Monopterus Albus culture pond should not be too deep. If the Monopterus Albus frequently swims to the surface to breathe, it will affect the normal growth, mostly because the pool water is too deep. Of course, the water should not be too shallow, otherwise the temperature will change too much. Generally speaking, the water depth of raising ricefield eel in the pond should be about 20cm to 30cm.

6. Monopterus Albus fed floating feed many times a day is a carnivorous omnivorous animal, which is eaten mainly by mouth, and the crisp sound can be heard when the water quality is fresh, mainly underwater feeding. Monopterus Albus eat bait has a certain fixed, suddenly change the type of bait, Monopterus Albus will refuse to eat, affecting the normal life and growth. If it is really necessary to change the bait, the proportion of the original feed should be gradually reduced and the proportion of the new feed should be increased to adjust. The first defecation time of Monopterus Albus is 24 hours after feeding, so feeding once a day can meet the feeding needs of Monopterus Albus [4]. The results showed that the body weight had no significant effect on the daily feeding rhythm of Monopterus Albus, and the feeding ratio of Monopterus Albus in different periods was in the following order: 20-00-22-00, 22-00-24-00, 0-00-20-0 and 4-0-0-1 600, respectively. In the outdoor artificial culture of Monopterus Albus, Monopterus Albus can be domesticated to develop the habit of regular fixed-point feeding, feeding once a day, and the appropriate feeding amount is about 80% of Monopterus Albus can be fed within 2 hours. The practice shows that the proportion of sunken feed of Monopterus Albus is obviously higher than that of floating feed, and the price of floating expanded feed is higher, so good sunken feed can be used.

7. Dark light is another habitat characteristic of Monopterus Albus, which is also beneficial to escape from enemy, but it is also the need of self-protection of the body. Unsheltered light for a long time (more than 10 days) will reduce the surface barrier function and immunity of Monopterus Albus, and the incidence rate increases rapidly, which indicates that the UV component of sunlight has a harmful effect on Monopterus Albus. Therefore, many farmers build shade on the pond, but it is easy to cause the light to be too dark. Many experiments have shown that low light conditions (less than 250lx) and still water environment inhibit the natural reproduction of Monopterus Albus, and the growth of aquatic plants is not good, which affects the purification of water quality. Therefore, Monopterus Albus culture should maintain a certain amount of light, aquatic plants should cover the surface of the water about 2GP3, and there should be shade in summer, astigmatism is the best.

8. The water temperature should not exceed the water temperature below 8 ℃ Monopterus Albus does not eat, below 5 ℃ begins hibernation, and 8 ℃ does not gain weight; Monopterus Albus generally suitable for growth at 15 ℃, the best growth temperature is 25 ℃ 32 ℃, if the water temperature is higher than 36 ℃, go to the hole for summer and die at 40 ℃. At present, in production, when the water temperature exceeds 30 ℃, cooling measures are taken immediately to avoid the influence of high temperature. Experiments have shown that Monopterus Albus has a high tolerance to high temperature and still shows a high appetite at 35 ℃, which is related to the fact that Monopterus Albus originated from the high temperature plains of India or the foothills of China and India. Therefore, in the artificial culture of Monopterus Albus in Nanjing and its southern area, the water temperature should be kept at about 30 ℃ in summer in order to make full use of solar energy resources, increase the food intake and growth rate of Monopterus Albus and shorten the culture cycle.

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