Methods of rearing eels
1, eel net-box farming
The use of net-box farming for eel farming is still in the stage of technological development. Nets are suitable for breeding in large bodies of water, the main advantage is that the water flow through the mesh, so that the box in the formation of a living water environment, and therefore the water quality is fresh, rich in dissolved oxygen, can be practiced in high-density intensive breeding. The main farming techniques are as follows:
The net box area of about 20 square meters is good, the net length of 5m, 4m wide, 1m high, the water part of the 40cm, the underwater part of the 60cm. the net quality should be good, the net mesh should be dense, the mesh should be tight to prevent the water rats to bite through the eel escape. Nets set in the water depth of 0.8m above the pond, the new net box into the water should be 35 days to be emitted by the harmful substances disappeared before stocking eel species. A few days before eel stocking, the water quality should be cultivated properly, so that the water color is thick and the transparency is about 15cm, which can control or reduce the infringement of ant mites on eels in the pond. Nets can be set side by side in the pond, two rows of nets in the middle of the bamboo frame for people to walk and feeding management. The area of the net box should not exceed 50% of the total area of the pond, otherwise it is easy to cause water quality deterioration. The net box placed in the water plants, preferably water peanuts, its coverage area should account for 90-95% of the net box area, for the growth of eel habitat to provide a good environment.
The eels have a habit of eating each other, so the stocking is basically the same specification is appropriate. Generally, each square meter can be stocked with 20kg of eel species, each net box stocking 400kg.Eels are accustomed to eating a kind of feed after it is difficult to change the habit of eating another kind of feed, so it should be fixed a few varieties of feed, such as earthworms, small fish, mussels, or animal offal, in order to improve its growth rate. Conditions can be put live bait, because of its high utilization rate, do not have to remove the residual bait, less pollution to the net box, is conducive to the growth of eels.
The most critical stage of eel net box culture is one month after stocking. This period is the eel to change the original habits, adapt to the process of the new environment. If the method is appropriate, the survival rate of eel species can reach more than 90%, the method is not appropriate, the survival rate is sometimes less than 30% or even all dead. This month is the key to the success or failure of eel net box culture, in addition to the eel species should do a good job of disinfection and domestication, should also be effective in controlling the occurrence of disease, the specific method is to use the water body of strong disinfectant and lime alternately disinfection, to put an end to the production of pathogens.2, eel plastic greenhouse soil-less aquaculture
Conventional pond culture, easy to disease and eel hibernation affects the year-round breeding. With the plastic greenhouse eel farming can be year-round continuous production, soilless aquaculture can effectively control the disease, so that the benefits doubled.
The most suitable temperature for eels is 27℃～30℃. Using plastic greenhouses, there is no need to set up heating devices, in spring, summer and fall, the temperature in the greenhouse is easy to maintain this temperature, even in winter, the average temperature in the greenhouse can reach 20 ℃.
The rearing pool maintains a slight flow of water, and the water quality will not deteriorate.
There are two main ways of soil-less running water breeding in plastic greenhouses:
1 Open type. Suitable for year-round warm running water place to build a pool. The advantage is that the flow is stable and suitable for larger scale operations. Feeding pools made of brick and cement, each pool area of 10 to 20 square meters, pool depth of 40 cm, 1 to 2 meters wide, pool ridge width 20 to 40 cm. In the relative position of the pool set up a diameter of 3 to 4 centimeters into the water pipe, drain pipe each 2. Inlet pipe and the bottom of the pool at the same height; drain pipe with the bottom of the pool at the same height, a 5 cm above the bottom of the pool. Inlet and outlet are equipped with metal mesh to prevent escape. A number of rearing pools are arranged side by side to become a unit, the area of each unit is best not more than 500 square meters.
2 Closed back to the circle filtration type. Suitable for use in large cities or places with a lack of water. The advantage is that the rearing water can be reused, less water consumption, easy to control the temperature, but the investment is slightly larger. Feeding pool construction method is the same as the open type. In addition to the need to build aeration tank, sedimentation tank, add some water purification devices, pumping devices and heating devices.
The construction of plastic greenhouses is the same as that of ordinary greenhouses, and it is better to put each unit in the same greenhouse so as to facilitate management.
Using the plastic greenhouse soil-less aquaculture this feeding method, because of the water quality is clear, as long as the feed is sufficient, eels generally will not escape. However, attention should be paid to prevent the harm of rats, snakes and other natural enemies. After feeding for a period of time, the same pool of eels appeared uneven in size, to separate in time to feed.
3. Eel rice paddy farming
Use of rice paddy eel farming, low-cost, easy to manage, both rice and fish production, is an effective way to get rich, increase income.
Selection of paddy fields and requirements
The paddy fields for eel farming should be selected with good water retention efficiency, low-lying terrain, and easy access to the fields.
One is to heighten and strengthen the ridge to achieve no water seepage and leakage; the second is to dig a set of ditches around the field inside and outside, which is 5m wide and 1m deep, and the other in the middle of the field to excavate a "+" or "well" type ditch, 50 cm wide and 30cm deep, and with the surrounding ring ditch connected; the other in the middle of the field to excavate "+" or "well" type ditch, width 50 cm, depth 30cm, and with the The third is to improve the water intake and drainage system, and in the water intake and drainage outlet to install a strong fish stopping facilities to prevent the escape of fish.
Putting seedlings
Time to focus on the middle and end of April, a one-time put enough, the fish stocking with 3 % - 4 % of salt water soak for 10 minutes, in order to prevent epidermal abrasions, and kill the water mold bacteria and surface parasites.
Feeding management
One is to improve the feeding of feed, eel is mainly animal bait omnivorous fish. In its predation of natural bait in the paddy field at the same time, depending on the eating situation, appropriate feeding pig's blood, small fish and shrimp and other feed to meet the needs of its eating growth; two is to do a good job of water quality management, paddy field water level to maintain a normal 10cm or so, and regularly refill the new water, the early general 3-5 days refill of new water once a day, the summer days every day refill of new water once a day, each time the water into the water to increase the depth of water 3 a 5 cm, in order to prevent the lack of oxygen; three is a regular Prevention and treatment of disease, once every six months with quicklime or bleach sprinkled around the ditch, and regular use of dysentery or fish blood san and other internal medicine mixed feed feeding, to prevent enteritis and other diseases.
Taking and overwintering
Putting in eel fry with specifications of about 50 grams of tail weight, after more than 5 months of feeding management, its specifications can reach about 150 grams of tail weight, and the big ones can reach more than 200 grams. The method of catching eels is relatively simple, in the early stage of the eel cage can be woven with bamboo gabions, put earthworms and other bait inside to trap them, and then put them in the cage in the evening, and then you can collect them in the early morning of the next day. After winter, eels have the habit of lurking in caves and shallow silt or water plants. If you want to take them, remove the water plants first, then increase the water level to draw eels out of their caves, and then put dry water to catch them. If the eel is stored in the field for the winter, it can be safely overwintered by keeping a certain depth of water or humidity in the ring ditch or by covering the surface of the soil with a layer of soft grass.
Sex control
Sex control is an effective way to increase production. Generally the use of sex hormones can induce the sex of eels to develop in the desired direction.
Treatment of eel fry with the male hormone methyltestosterone can obtain more than 99% male fish. The treated fish are not only fast-growing but also low-cost because of their single sex and fixed density, which generally increases production by about 30 percent.
The technology of controlling sex has been developed for many years in foreign countries, and the technology has been very mature, but in China, the technology only stays at the laboratory level, and there is no relevant report on production, and the corresponding national standard has not been perfected.
Precautions
1, the choice of seedling: must choose a strong body without injury, swimming lively, neat specifications, muscle fat, body surface without parasites, body color is bright yellow eel species. For the body surface white, broken skin, broken tail, mouth and gill bones have scars, are not suitable for stocking.
2. Preparation before stocking: After sterilizing the eel pond and filling it with water, you can put the eel seeds when the water temperature is above 15℃. Before stocking, the eels should be soaked in 10ppm bleach or 3%-4% salt water for 15-20 minutes to kill the pathogens on their body surface.
3, disease control:
1 "cold" disease. Due to the injection of new water with the original water temperature difference is too large. As long as the water temperature is adjusted so that it is stable, you can prevent and control this disease.
2 capillary nematode disease. Parasitic in the eel body, so that the fish wasting death, and accompanied by edema, *** redness. Each kilogram of eel with 90% crystal trichlorfon 0.1 grams, mixed into the feed feeding, 6 consecutive days, can be.
3 plum blossom spot disease. The eel body has soybean-sized plum blossom spot-like ulcerated spots in many places.
4 eel net box culture due to high density, when the feed is not enough to put each other will bite and make the infection of mold, the growth of "white hair" on the surface of the body, the sick fish loss of appetite and death. The treatment is to splash with salt water and baking soda. In the case of sufficient feed, not only can avoid this phenomenon, even if the eel species stocked in the same net box specification difference is large, will not occur when the phenomenon of mutual cannibalism.
5The feed fed in the net box culture should be fresh, can't feed the spoiled feed, part of the remaining rotting and stinking feed in the net box should be removed in time, otherwise it is easy to cause enteritis disease. The treatment method can be sulfonamides, furans or garlic taken internally. The feed should be washed and dipped in 200ppm potassium permanganate for 3 minutes before putting it into the net, and then drenched with water before feeding. If artificial compound feed is used, its protein content should be more than 45%, and the maggot pulp should be used as erbium and domesticated in order to achieve good results.
6 Eel species in the fishing, transportation and stocking process should try to avoid abrasions, in order to prevent bacterial invasion of the occurrence of red skin disease, the symptoms of hemorrhage, inflammation of the body surface to the abdomen and the sides of the most obvious, in the form of lumps, the need for internal medicine and disinfection of the external combination of medicines and disinfection treatment. Prevention method: eel seed stocking strict disinfection, the specific method is 100kg of water plus 50ml aquatic seedling disinfectant immersion 30 minutes, or 8% iodine-containing salt water immersion for 10 minutes, and then put people in the water for 1 hour, and then by the water can be put into the box after washing again.
In addition, the water should be frequently disinfected. Disinfection can be used lime, dosage 100 ~ 150 g / m3 malachite green CuSO4, dosage 0.7 g / m3, bleach, dosage 10 g / m3.
4, net box culture in the eel in the container high-density placement, the body surface more and more mucus through the decomposition of microorganisms in the water, quickly consumed the dissolved oxygen in the water, resulting in eel species death. The eel species will sometimes be entangled with each other in the net box, sometimes more than 100 pounds of eel species entangled together, resulting in a large number of eel species death.
Preparation for eel farming
1, eel pool construction
To choose a slightly higher terrain, drainage and irrigation is convenient to build a pool, can be built on the ground pool, underground pool or semi-underground pool. The area of 30~50 m2 is suitable, the wall and bottom of the pool should be polished smooth, so as to avoid eels in the activities of the panel caused by a variety of bacterial, viral infections; pool depth of 80~100 cm, the pool shape is generally rectangular, oval or square, east-west direction. And set the natural overflow, inlet and outlet pipe with wire mesh firmly closed to prevent eels from escaping. The top of the pool should be higher than 30 cm above the water level, and the top of the pool wall can be made into a "T" shape. The bottom layer of 20~30 cm river mud or composted loam with grass, cow dung, mud layer above the water level to maintain 20~25 cm is appropriate, 1/3 of the surface of the water surface of the pool can be planted moderately wild rice, water peanuts, water hyacinth, artemisia, and other aquatic plants for the eel shade, but also to reduce the temperature of the water, to improve the environment of the fish pond.
2, seedling selection and stocking
Seedling from cage-caught wild eels, can also be purchased from the market, but the injured broken skin, broken tail eel to be removed, it is best to choose artificially propagated seedling. Seedlings should be selected from eels that are robust, smooth, active and uniform in size. The general requirements of the weight of 20 g / tail is appropriate, can also be put 30 ~ 50 g / tail of large-size eels.
Fifteen days before stocking, use 10 mg/kg of copper sulfate and 100 mg/kg of potassium permanganate mixture for the whole pool, soak for 7 d, and then replace with clean water. Before stocking, in order to determine whether there is residual toxicity in the fish pond, we can use bighead carp or silver carp fry with body length of 5~10 cm to make 2~3 fish/m2 as "test fish", if the fish activities are normal, the toxicity in the pond has disappeared, on the contrary, stocking should be postponed. Stocking time in early spring is good, within 1 week to put all. The stocking amount is generally 1.5~3.0 kg/m2, and the good condition can be put into 5~6 kg/m2. Before eel stocking, use 4% saline or 10 mg/kg bleach to soak for 10~20 min to eliminate the pathogens and parasites on the surface of the fry and increase the resistance to disease. When stocking, it is necessary to pay attention to the water temperature difference between the holding tank and the stocking tank should not be too large, not more than 3 ℃. If the difference is large, the water temperature should be adjusted appropriately.