Rice field eel cage culture techniques, suitable for both ponds and ditches

The rice field eel is rich in nutrients, has delicious meat, and has nourishing and health-promoting effects, and is deeply loved by consumers. Raising rice field eels requires little investment, has a short cycle, produces quick results, and brings high economic returns, making it a very good rural side business. Using existing fish ponds and ditches for cage culture of rice field eels does not affect the output of conventional aquaculture, and can also grow small-sized rice field eels into large-sized commercial eels. It does not occupy land, saves pond construction costs, and increases the economic benefits of aquaculture. The specific culture conditions and methods are as follows:

1. Conditions of ponds and ditches. Ponds and ditches with an area of 3 to 5 mu are all suitable, and the average water depth during the culture season should be above 1.5 m. Fish fry are stocked in ponds and ditches as usual. The water quality of the culture water body is good, pollution-free, with a pH value of about 7.2, relatively rich dissolved oxygen, and high transparency. 2. Cage specifications. The cage is 3 m long, 2 m wide, and 1.5 m high. Use polyethylene mesh sheets with good quality, dense mesh, and tightly woven strands. The mesh size depends on the size of the rice field eels being cultured, following the principle of preventing eel escape and facilitating water exchange inside and outside the cage. 3. Cage installation. In ponds, 40 cages can be set up per mu, and in ditches, 30 cages can be set up per mu. The spacing between cages is about 3 m. In ponds, each cage is fixed with 6 bamboo stakes. Because the water level in ditches changes greatly, floating-frame cages are used so that the cage body naturally rises and falls with changes in water level. One week before stocking the rice field eels, soak the newly made cages in water so that a layer of biofilm attaches to the surface of the mesh, making it softer, so as to avoid disease caused by skin abrasions on the rice field eels. Set up 1 to 2 feeding platforms in each cage, with the feeding platform about 5 cm from the water surface. 4. Artificial transplanting of aquatic plants. Transplant water peanut into the cages, with its coverage accounting for about 80% of the cage area. This can not only purify water quality, but also provide a hiding place for the rice field eels, which is beneficial to their growth. The transplanted water peanut is best with roots removed and washed clean, then soaked in 50 g of salt water for about 10 min to prevent harmful organisms such as leeches from being brought into the cages with the grass. 5. Stocking. (1) Fish fry stocking. Before stocking fish fry, first clear the pond with quicklime. For dry pond clearing, use 120 kg of quicklime per thousand sq m. After the effect of the medicine disappears, stock the fish fry, averaging 60 kg per thousand sq m. Before the fish fry enter the pond, soak them in 40 g of salt water for 15 min. (2) Eel fry stocking. The eel fry stocked are mainly wild seedlings caught with eel traps from water areas such as rice fields and ditches, with an average body weight above 30 g, and the large ones reaching above 100 g. The size stocked in each cage should be as uniform as possible to prevent cannibalism. The stocked eel fry are required to be lively and robust, disease-free and injury-free, with smooth and shiny body surfaces. There are three body colors of eel fry: yellow, green, and red. Yellow large-spotted eels are the best and grow the fastest; green eels are second. In addition, 1-2 kg of loach are also stocked in each cage, using the loach's habit of swimming up and down to provide partial oxygenation. Loach does not compete for food with rice field eels, can remove leftover bait of the rice field eels, and can also prevent the rice field eels from tangling with each other in still water due to high density, reducing the occurrence of diseases. The stocking time is mainly after June 15. Before each stocking, disinfect the eel body with disinfectants such as glutaraldehyde. The soaking disinfection time is determined according to water temperature and the actual tolerance of the rice field eels, generally 5-10 min. 6. Feeding methods. In cage culture of rice field eels, the first task is to do a good job of diet training. Newly stocked rice field eels should be fed only after 3-4 d. At the beginning, the feeding amount should be small. Mix earthworms into the conventional feed to be used for a long time afterward, such as wheat flour, silkworm pupa powder, small trash fish, and snail meat. Generally, it is better to mix several kinds of feed evenly and make them into strips, then put them regularly on the feeding platform. At first, the feeding time is about 1 h before sunset each day, once a day; after diet training is completed, feed twice a day, that is, add one feeding at 9:00 in the morning. The morning feeding amount accounts for about 30% of the whole day. The specific daily feeding amount is mainly controlled flexibly according to weather, water temperature, water quality, and the activity of the rice field eels. In principle, it is generally considered appropriate to finish eating within about 2 h after each feeding. 7. Daily feeding management. First, do a good job in feeding. It is best that the eel fry in each cage are stocked on the same day, and at most not more than 2 d, otherwise it will cause difficulty in diet training. After diet training is successful, feed according to the “four fixed” principles of fixed quality, fixed quantity, fixed location, and fixed time. Second, there must be a specially assigned person responsible for feeding management. During the main growth period from April to the end of October, inspect the cages twice a day, morning and evening, to check whether the mesh is damaged and whether the mesh openings are blocked. Frequently observe the activity and feeding conditions of the rice field eels. After heavy rain, adjust the depth of the cages in the pond according to the water level. During the flood season, pay even more attention to preventing branches, debris, and other objects washed in by large water from cutting the cages and causing eel escape. Third, regularly remove dirt in the cages, promptly take out dead eels, and regularly wash and brush the cages to ensure water exchange inside and outside the cage. Dead water peanut should be promptly taken out and replaced with new ones, and residual bait on the feeding platform should be promptly removed to avoid rotting and deteriorating and affecting water quality. 8. Disease prevention and control. Wild rice field eels rarely suffer from diseases, but under artificial high-density culture conditions, due to changes in ecological conditions, diseases are prone to occur, so disease prevention and control work must be done well, implementing the policy of “prevention first, early treatment when diseased.” To prevent eel diseases, in addition to selecting good eel fry and disinfecting the eel body during stocking, from May to September, hang bags with bleaching powder or chlorine dioxide once every half month, with 2 bags hung per cage and 150 g of medicine placed in each bag; in addition, add “Yukangda” or “florfenicol” to the feed for feeding once every half month for 3 consecutive d. Once disease occurs, apply the right medicine according to the condition. Because water exchange in ponds is slow, drugs can be directly used to disinfect the water body in the cages. In ditches, however, because the water body flows, when splashing drugs in the cages, it is necessary to first surround the cages with plastic film or colored striped cloth so that the water body cannot exchange temporarily, and then disinfect the water body in the cages according to the medicated bath concentration. The disinfection time should be controlled flexibly according to the tolerance of the rice field eels.