CATDOLL : CATDOLL: How to raise eels and what do eels eat?

How to raise eels and what do eels eat?

Eels mainly live in mud and forage for food at night. Eels mainly feed on mud microorganisms and aquatic snails. If they are raised, weeds can be mixed into the mud to oxidize them, but attention should be paid to the water quality. Earthworms are also the staple food of eels. The ratio of water to mud should be 10 centimeters of water for every 30-50 centimeters of mud depth.

Yellow eels like to eat earthworms the most. You can usually get some cooked corn, potatoes, etc.

We have maggots here.

How to culture eels without soil in cement pond?

Farming technology

1. Operation procedures of still water and soilless ecological breeding technology for yellow eel

There is a lot of content in the still water and soilless ecological breeding technology of rice field eels. The key technologies include shallow water semi-artificial breeding technology of rice field eels, compound feed domestication technology, and pest and disease control technology. Among them, eel species screening and processing are the key to the success of rice field eel breeding.

2. Construction and treatment of eel ponds

The construction of eel ponds should take into account the following five design principles: simulate the natural environment; convenient drainage and irrigation, conducive to heat preservation; conducive to taming and feeding compound feed; conducive to preventing and controlling diseases and pests of yellow eels; escape prevention, easy capture and convenient management. The area of ​​outdoor static water soilless breeding ponds is 15-20m2, and the indoor breeding area is smaller, generally 6-10 m2. Pool wall height: 20-30cm indoors, 40-50cm outdoors. The wall can be built with a single brick, cement is applied inside, and the top of the wall is horizontally built with bricks in a "T" shape. Plastic film pools can also be used for breeding. Several small pools of the same specifications are strung together in a row, but the inlet and outlet are independent to prevent diseases and pests from spreading to each other. The shape of the fish pond is preferably rectangular or square. The outlet is slightly lower than the bottom of the pool to ensure thorough sewage discharge; the water inlet is set just above the food table, opposite to the outlet, and the position should be high, generally 15-20cm from the bottom of the pool; the overflow outlet is 25cm from the bottom of the pool, and the overflow outlet is not required for indoor breeding. The diameter of each water outlet is about 5-6cm and should be covered with a nylon net to facilitate the discharge of feces and prevent the eels from escaping.

After the cement pool is built, it must be de-alkali treated. Using a new pool without de-alkali treatment is one of the main reasons for the failure of many farmers. The method is: soak it with phosphate fertilizer (1 kg of phosphate fertilizer for 1 ton of water) or acetic acid for a week, drain the soaking water and replace it with clean water; or fill it with water and soak it for 30 days (it is best to put grass piles to ferment), and then drain it. Plastic film pools do not need to be de-alkali treated.

Fish nests are very important in static water and soilless culture. Various pipes, bamboo tubes, brick gaps, water plants, etc. can be used as fish nests. Since eels have a certain degree of aggregation, the area of ​​the fish nest should not be too small. The general principle of setting up eel nests is: it is convenient for eels to enter and exit freely, the interior is dark and lightless, and there is enough space. In production, it is generally better to use waste bicycle tires disinfected with potassium permanganate solution as eel nests. The tires are placed under the water plants, and 5-6 tires can be placed in each small pool. Bamboo tubes of about 2m can be used. The size of the hole depends on the eel body. It is appropriate to be larger than the eel. Every two bamboo tubes are in a row, and each pool has 3-5 rows, with a spacing of about 0.3m between each row. Bricks are placed under each row of bamboo nests to make a large space under the bamboo nests, which is convenient for water flow and sewage discharge. In order to fix the bamboo nests, it is best to press bricks above the hole, which also plays a role in shading and shading.

3. Aquatic Plant Stocking

"To raise fish, you must first raise water, and to raise water, you must first raise grass." The placement of aquatic plants is one of the key technologies for static water soilless farming. Reasonable placement of aquatic plants to purify water quality can reduce the number of water changes in the eel pond to once a month, saving water and labor, and can prevent heatstroke, reduce stress reactions, provide fish nests, and prevent diseases and insect pests. Aquatic plants are selected according to the standards of "preventing fish from escaping, growing fast, purifying water quality, and facilitating fish hiding." Common ones include water peanuts, water hyacinths, water lilies, and fine green duckweed. The planting area of ​​aquatic plants should not exceed 2/3 of the total pond area. At least 1/3 of the fish pond area should be left empty to set up a feeding table and facilitate the activities of yellow eels. In different seasons, aquatic plants should be reasonably matched in a certain proportion. In summer, water hyacinths and water lilies are the main ones, while in spring and autumn, water peanuts and fine green duckweed are the main ones. In winter, no aquatic plants are left to prevent yellow eels from freezing under the aquatic plants. Generally, aquatic plants are put in 15 days before stocking eels. Before putting in, they should be disinfected by soaking in 100g/m3 potassium permanganate solution for 0.5h, or by soaking in 10g/m3 copper sulfate solution for insecticide.

In daily management, excess aquatic plants should be removed in time or overly long aquatic plants should be cut. In combination with eel pond disinfection, 10g/m3 quicklime or 0.7g/m3 copper sulfate solution should be sprinkled on the grass to prevent aquatic plant pathogen infection.

4. Eel species selection

The key to successful eel farming is the quality of seedlings. At present, the large-scale breeding technology of eels has not yet been mastered, and the seedlings used in production are basically from wild resources. There are many ways to catch wild eels, including cage catching, hook fishing, electric shock, shovel digging, clamp catching, net lifting and drug catching. Some wild eels have been transferred and stored and transported many times, and some wild eels themselves carry diseases and insect pests. Therefore, the quality of wild eel seedlings purchased from the market is uneven, and strict screening is very important in production.

There are many methods for screening eel seedlings. The sensory screening method (based on body color, external injuries, strength, mucus, etc.), water flow screening method, behavioral screening method, and burrowing screening method are highly subjective and cannot screen eels with latent diseases in the body. It is also rather troublesome to screen them one by one. The drug immersion method is highly irritating to eels, the drug concentration is difficult to control, and the operation is rather troublesome. The feeding screening method has a better screening effect, but there are no reports on its specific operation process and quantitative method.

The eel selection method we use in production is: put the eel seedlings in a plastic container in shallow water at a certain density, soak them in medicine, feed them a fixed amount of empty mealworm larvae for 5 consecutive days, change the water once every morning, and check the eel's food intake. In the range of 18-30℃, if the average daily food intake of the eel exceeds 0.5% of the eel's body weight, then keep the seedlings; if the average daily food intake of the eel is less than 0.5% of the eel's body weight, then eliminate the seedlings. The eel stocking time is generally 10-15 days after the water plants are released.

5. Semi-artificial breeding technology of yellow eel

The semi-artificial breeding technology of the yellow eel has the advantages of high fertilization rate and hatching rate, concentrated breeding time, convenient management and high efficiency, and is an inevitable trend for the large-scale breeding of yellow eels. The breeding pond is designed and built according to the requirements of static water soilless breeding, with an area of ​​20-30m2. The types of aquatic plants vary from place to place, including water hyacinth (Eichhornia Crassipes Solm.), water peanut (Alternanthera Philoxeroides Griseb), water lily (Pistia stratiotes), and goldfish algae (Ceratophyllum demersum). From March to July each year, 10 parent eels are stocked per square meter of the breeding pond (female: male ratio is 6:4). The management method is the same as static water soilless ecological breeding, but the number of water changes is increased during the breeding season (May to August), that is, the water is changed once every 7 days, the water depth is 20-25cm, and the pH is 6.0-8.5. After the yellow eel lays eggs, it is promptly fished out for artificial incubation, and the unfertilized eggs should be removed in time. The drip incubation method is: the incubator is a shallow dish of 40cm×40cm×7cm, with 2cm thick sterilized river sand on the bottom, water drips in from a high container and overflows from the side wall of the dish, the water depth is kept at about 5cm, and the daily temperature difference does not exceed 2℃. When the fertilized eggs just enter the incubator, the water dripping frequency is 10 drops/min, which lasts for 24 hours, and then the water dripping speed is gradually increased until the seedlings are hatched.

6. Eel Taming

Rice field eels are very selective about food, and once they adapt to a certain food, it is difficult for them to change their eating habits. At present, the artificially cultured eels mainly come from wild eels that eat live bait. If they are fed with live bait alone, it is not conducive to the healthy growth of rice field eels, and it increases the input cost, and may be limited by the fact that feed resources cannot be available for a long time. If they are fed with compound feed or a small amount of live bait is mixed into compound feed, it is possible to effectively reduce feed costs, ensure comprehensive nutrition, facilitate the addition of additives and drugs, and prevent and control diseases and insect pests. Therefore, feeding compound feed is an important measure to develop the rice field eel farming industry.

1. Taming conditions

(1) The feeder must be patient. The feeding process takes at least 7-10 days. It is normal to succeed in feeding within 10-30 days.

(2) The eel pond should be small, generally 15-20m2. The eel feeds by using its sense of smell, taste and lateral line system in an integrated manner. The eel must be within an effective range to find and prey on food.

(3) Feeding training must be based on the four principles of “fixed location, fixed time, fixed quality and fixed quantity” that the eel can eat.

(4) Feeding should be done according to the season, weather and the size of the eel species. For example, it is very suitable for feeding eels when they just finish hibernation, the temperature rises and they start to feed.

(5) If it is a wild eel, the leeches should be carefully screened and killed, and the eel should be domesticated and eaten after being stabilized for a period of time.

(6) It is not advisable to release loaches or other fish into the water before taming the eels. Releasing them too early will cause them to compete with the eels for food, which will be detrimental to taming the eels.

2. Food Taming Method

Taking advantage of the eel's swallowing and greedy characteristics, live bait is mixed with compound feed for feeding training. It is necessary to master the eel's start feeding time, peak feeding time and finishing time to facilitate artificial feeding training.

(1) Before training, the eels must be starved for 1-2 days without being fed any food.

(2) Before starting to train the eels, feed them with live bait that accounts for about 1% of their weight for 2-3 days, such as river frogs, earthworms, mealworms, etc., and the "four determinations" must be achieved.

(3) After stopping feeding for another 1-2 days, make the compound feed and live bait into a "cake" style, that is, cut part of the live bait into pieces and mix it with the compound feed, and stick part of it to the outside, or use a dough press to press it into thin strips for feeding. The total amount is about 1% of the weight of the stocked eels. On the first day, it is 80% live bait and 20% compound feed, on the 2nd-3rd day, it is 60% live bait and 40% compound feed, on the 4th-5th day, it is 40% live bait and 60% compound feed, and so on. Generally, it will take 7-10 days for the eels to be fully tamed and eat artificial compound feed.

(4) During the feeding process, observe the leftover food, water quality and excrement every day to judge the feeding situation of the eel. If the feeding is abnormal, remove the leftover bait and reduce the proportion of compound feed or appropriately reduce the feeding amount. If the eel still cannot eat normally, stop feeding for 1-2 days and then continue. If the eel can finish eating, gradually increase the proportion of compound feed until the feeding is successfully trained. After the feeding is successfully trained, immediately mix drugs into the compound feed to kill parasites. For the eels that have been successfully trained, make the compound feed into dry granules the size of mung beans or peas and feed them. The total amount should also be gradually increased to 2%-10% of the eel weight, and then enter the daily management work.

7. Summer Shade

The still water soilless breeding pond for yellow eel is small (15-20m2), with shallow water level (about 15-20cm), and the water temperature can easily exceed 30℃ in summer. Shading is an essential step to avoid the heat. Generally, a shade net is set up on the pond, and climbing plants such as grapes, loofah, trichosanthes, and pumpkins are planted by the pond. But pay attention to leaving 10% to 30% of light on the surface of the pond. At the same time, when the temperature exceeds 33℃, the water level in the pond should be deepened to reduce the density of yellow eels, and new water should be slowly injected. Groundwater can be used to adjust the water temperature of the eel pond.

8. Water quality control

The pH value, transparency, dissolved oxygen, ammonia nitrogen, temperature, nitrite and sulfide of the aquaculture water are the main ecological factors that induce fish diseases besides pathogens. To maintain good water quality in the eel pond, the following points are generally required:

(1) Drug control. Every 10 to 15 days, use 10g/m3 of quicklime or 1g/m3 of bleaching powder to spray the whole pond. In the north, the water quality is alkaline, so bleaching powder should be used more often; in the south, the water quality is acidic, so quicklime can be used more often. Mix oxytetracycline, sulfonamides and other drugs into feed for oral administration. Each drug should be used for 3 to 5 days, and then used alternately every 20 to 30 days.

(2) Maintain a suitable water level. If the water level is too deep, the water temperature will drop, and the water quality will not be easy to improve. In addition, the eel needs to stick its head out of the water frequently to eat and breathe. To reduce the eel's physical consumption, the water level should be shallow. However, if the water level is too shallow, the water temperature will change dramatically, and the eel's activity space will be small, which is extremely unfavorable for the eel's growth and development. The general water level is 15-20 cm, and it can be deepened to 30 cm when the temperature is high. The water level may also change under special circumstances. For example, the water level in the seedling pond, the pond for sale, and the sick eel pond should be shallow, while the water level in the adult eel breeding pond can be deeper. If the aquatic plants grow luxuriantly, it is sufficient to change the water once a month. Generally, fresh water should be added in time according to the amount of water evaporation, but the leftover food on the feeding table should be cleaned every day to avoid deteriorating the water quality. When changing the water, the temperature difference between the inlet water and the water in the pond should be controlled. The temperature of small eels should not exceed 2°C, and that of large eels should not exceed 5°C. The daily temperature difference of the water temperature should be less than 10°C. It is best to build a reservoir to facilitate water changes.

(3) Maintain biodiversity. Eel ponds should be stocked with golden apple snails, field snails, small fish, loaches, etc. to remove residual bait and regulate water quality. Many organisms are also indicators of water quality. However, it is important to maintain a reasonable proportion of these organisms in terms of quantity. Generally, the food intake (dry weight) of yellow eels is 1% to 2% of their body weight, and the dry weight of fish feces is 2% to 10% of their food intake. Generally, the stocking density of eels does not exceed 3kg/m2. Calculated based on the dry food intake of loaches being 2% to 4% of their body weight, the number of loaches stocked per m2 of eel pond should not exceed 0.3kg. Loaches should be stocked after yellow eels have been tamed and fed with compound feed, so that they can fully play the role of eating yellow eel feces and preventing yellow eels from "fevering". Stocking toads is particularly effective in preventing the yellow eel's unique plum spot disease. Generally, 1 to 2 toads can be stocked in each small pond. The stocking density of snails should not exceed 0.25kg/m2. In addition, appropriate amount of green algae can be cultivated and photosynthetic bacteria (PSB) can be added.

Observing the water color is the key to regulating water quality. Generally, yellow-green, blue and clear water is good. Brown, gray or black water is abnormal and remedial measures should be taken in time.

IX. Diseases and prevention of eel farming

Disease prevention and treatment of eels The eels have relatively strong disease resistance and rarely get sick during artificial breeding. However, if they are poorly managed or the environmental factors are seriously adverse, their growth rate and survival rate may be affected.

1. Construction of cement pool

Choose a place with good lighting, warm and ventilated environment, convenient transportation, sufficient water source, convenient water inlet and outlet, and no pollution source within 3 kilometers to build a pond.

2. Loach stocking

It is best to use wild loach seedlings caught in cages. There are two ways to grow loach seedlings: directly growing them in the same year and growing them in the next year. For growing loach seedlings directly in the same year, the loach seedlings with a body length of 3-5 cm are grown in June and harvested in June-August of the following year.

3. Feeding

Loaches have a mixed diet and can eat both natural and artificial baits. Artificial baits mainly include animal feeds such as maggots, earthworms, snails and clams, fish meal, silkworm pupae, pig blood, livestock and poultry waste, and plant feeds such as grains, wheat bran, rice bran, bean dregs, soy sauce residue, vegetable cakes, and cake dregs.

Nutritional value and efficacy of eel:

The eel has no scales, is yellow-brown in color, has irregular dark spots on the sides of its body, has underdeveloped and almost disappeared fins, has only one three-edged spine on its body, and is tender and delicious. The eel is rich in nutritional value, rich in protein, fat, calcium, phosphorus, iron, vitamins and a variety of phytochemicals, and is a good tonic. It is mainly used to treat deficiency of qi and blood, and weakness caused by chronic diarrhea and dysentery. The eel also has the effect of dredging meridians and benefiting joints, so patients with rheumatism can choose to eat it or soak it in wine.

Farming technology

1. Operation procedures of still water and soilless ecological breeding technology for yellow eel

There is a lot of content in the still water and soilless ecological breeding technology of rice field eels. The key technologies include shallow water semi-artificial breeding technology of rice field eels, compound feed domestication technology, and pest and disease control technology. Among them, eel species screening and processing are the key to the success of rice field eel breeding.

2. Construction and treatment of eel ponds

The construction of eel ponds should take into account the following five design principles: simulate the natural environment; convenient drainage and irrigation, conducive to heat preservation; conducive to taming and feeding compound feed; conducive to preventing and controlling diseases and pests of yellow eels; escape prevention, easy capture and convenient management. The area of ​​outdoor static water soilless breeding ponds is 15-20m2, and the indoor breeding area is smaller, generally 6-10 m2. Pool wall height: 20-30cm indoors, 40-50cm outdoors. The wall can be built with a single brick, cement is applied inside, and the top of the wall is horizontally built with bricks in a "T" shape. Plastic film pools can also be used for breeding. Several small pools of the same specifications are strung together in a row, but the inlet and outlet are independent to prevent diseases and pests from spreading to each other. The shape of the fish pond is preferably rectangular or square. The outlet is slightly lower than the bottom of the pool to ensure thorough sewage discharge; the water inlet is set just above the food table, opposite to the outlet, and the position should be high, generally 15-20cm from the bottom of the pool; the overflow outlet is 25cm from the bottom of the pool, and the overflow outlet is not required for indoor breeding. The diameter of each water outlet is about 5-6cm and should be covered with a nylon net to facilitate the discharge of feces and prevent the eels from escaping.

After the cement pool is built, it must be de-alkali treated. Using a new pool without de-alkali treatment is one of the main reasons for the failure of many farmers. The method is: soak it with phosphate fertilizer (1 kg of phosphate fertilizer for 1 ton of water) or acetic acid for a week, drain the soaking water and replace it with clean water; or fill it with water and soak it for 30 days (it is best to put grass piles to ferment), and then drain it. Plastic film pools do not need to be de-alkali treated.

Fish nests are very important in static water and soilless culture. Various pipes, bamboo tubes, brick gaps, water plants, etc. can be used as fish nests. Since eels have a certain degree of aggregation, the area of ​​the fish nest should not be too small. The general principle of setting up eel nests is: it is convenient for eels to enter and exit freely, the interior is dark and lightless, and there is enough space. In production, it is generally better to use waste bicycle tires disinfected with potassium permanganate solution as eel nests. The tires are placed under the water plants, and 5-6 tires can be placed in each small pool. Bamboo tubes of about 2m can be used. The size of the hole depends on the eel body. It is appropriate to be larger than the eel. Every two bamboo tubes are in a row, and each pool has 3-5 rows, with a spacing of about 0.3m between each row. Bricks are placed under each row of bamboo nests to make a large space under the bamboo nests, which is convenient for water flow and sewage discharge. In order to fix the bamboo nests, it is best to press bricks above the hole, which also plays a role in shading and shading.

3. Aquatic Plant Stocking

"To raise fish, you must first raise water, and to raise water, you must first raise grass." The placement of aquatic plants is one of the key technologies for static water soilless farming. Reasonable placement of aquatic plants to purify water quality can reduce the number of water changes in the eel pond to once a month, saving water and labor, and can prevent heatstroke, reduce stress reactions, provide fish nests, and prevent diseases and insect pests. Aquatic plants are selected according to the standards of "preventing fish from escaping, growing fast, purifying water quality, and facilitating fish hiding." Common ones include water peanuts, water hyacinths, water lilies, and fine green duckweed. The planting area of ​​aquatic plants should not exceed 2/3 of the total pond area. At least 1/3 of the fish pond area should be left empty to set up a feeding table and facilitate the activities of yellow eels. In different seasons, aquatic plants should be reasonably matched in a certain proportion. In summer, water hyacinths and water lilies are the main ones, while in spring and autumn, water peanuts and fine green duckweed are the main ones. In winter, no aquatic plants are left to prevent yellow eels from freezing under the aquatic plants. Generally, aquatic plants are put in 15 days before stocking eels. Before putting in, they should be disinfected by soaking in 100g/m3 potassium permanganate solution for 0.5h, or by soaking in 10g/m3 copper sulfate solution for insecticide.

In daily management, excess aquatic plants should be removed in time or overly long aquatic plants should be cut. In combination with eel pond disinfection, 10g/m3 quicklime or 0.7g/m3 copper sulfate solution should be sprinkled on the grass to prevent aquatic plant pathogen infection.

4. Eel species selection

The key to successful eel farming is the quality of seedlings. At present, the large-scale breeding technology of eels has not yet been mastered, and the seedlings used in production are basically from wild resources. There are many ways to catch wild eels, including cage catching, hook fishing, electric shock, shovel digging, clamp catching, net lifting and drug catching. Some wild eels have been transferred and stored and transported many times, and some wild eels themselves carry diseases and insect pests. Therefore, the quality of wild eel seedlings purchased from the market is uneven, and strict screening is very important in production.

There are many methods for screening eel seedlings. The sensory screening method (based on body color, external injuries, strength, mucus, etc.), water flow screening method, behavioral screening method, and burrowing screening method are highly subjective and cannot screen eels with latent diseases in the body. It is also rather troublesome to screen them one by one. The drug immersion method is highly irritating to eels, the drug concentration is difficult to control, and the operation is rather troublesome. The feeding screening method has a better screening effect, but there are no reports on its specific operation process and quantitative method.

The eel selection method we use in production is: put the eel seedlings in a plastic container in shallow water at a certain density, soak them in medicine, feed them a fixed amount of empty mealworm larvae for 5 consecutive days, change the water once every morning, and check the eel's food intake. In the range of 18-30℃, if the average daily food intake of the eel exceeds 0.5% of the eel's body weight, then keep the seedlings; if the average daily food intake of the eel is less than 0.5% of the eel's body weight, then eliminate the seedlings. The eel stocking time is generally 10-15 days after the water plants are released.

5. Semi-artificial breeding technology of yellow eel

The semi-artificial breeding technology of the yellow eel has the advantages of high fertilization rate and hatching rate, concentrated breeding time, convenient management and high efficiency, and is an inevitable trend for the large-scale breeding of yellow eels. The breeding pond is designed and built according to the requirements of static water soilless breeding, with an area of ​​20-30m2. The types of aquatic plants vary from place to place, including water hyacinth (Eichhornia Crassipes Solm.), water peanut (Alternanthera Philoxeroides Griseb), water lily (Pistia stratiotes), and goldfish algae (Ceratophyllum demersum). From March to July each year, 10 parent eels are stocked per square meter of the breeding pond (female: male ratio is 6:4). The management method is the same as static water soilless ecological breeding, but the number of water changes is increased during the breeding season (May to August), that is, the water is changed once every 7 days, the water depth is 20-25cm, and the pH is 6.0-8.5. After the yellow eel lays eggs, it is promptly fished out for artificial incubation, and the unfertilized eggs should be removed in time. The drip incubation method is: the incubator is a shallow dish of 40cm×40cm×7cm, with 2cm thick sterilized river sand on the bottom, water drips in from a high container and overflows from the side wall of the dish, the water depth is kept at about 5cm, and the daily temperature difference does not exceed 2℃. When the fertilized eggs just enter the incubator, the water dripping frequency is 10 drops/min, which lasts for 24 hours, and then the water dripping speed is gradually increased until the seedlings are hatched.

6. Eel Taming

Rice field eels are very selective about food, and once they adapt to a certain food, it is difficult for them to change their eating habits. At present, the artificially cultured eels mainly come from wild eels that eat live bait. If they are fed with live bait alone, it is not conducive to the healthy growth of rice field eels, and it increases the input cost, and may be limited by the fact that feed resources cannot be available for a long time. If they are fed with compound feed or a small amount of live bait is mixed into compound feed, it is possible to effectively reduce feed costs, ensure comprehensive nutrition, facilitate the addition of additives and drugs, and prevent and control diseases and insect pests. Therefore, feeding compound feed is an important measure to develop the rice field eel farming industry.

1. Taming conditions

(1) The feeder must be patient. The feeding process takes at least 7-10 days. It is normal to succeed in feeding in 10-30 days.

(2) The eel pond should be small, generally 15-20m2. The eel feeds by using its sense of smell, taste and lateral line system in an integrated manner. The eel must be within an effective range to find and prey on food.

(3) Feeding training must be based on the four principles of “fixed location, fixed time, fixed quality and fixed quantity” that the eel can eat.

(4) Feeding should be done according to the season, weather and the size of the eel species. For example, it is very suitable for feeding eels when they just finish hibernation, the temperature rises and they start to feed.

(5) If it is a wild eel, the leeches should be carefully screened and killed, and the eel should be domesticated and eaten after being stabilized for a period of time.

(6) It is not advisable to release loaches or other fish into the water before taming the eels. Releasing them too early will cause them to compete with the eels for food, which will be detrimental to taming the eels.

2. Food Taming Method

Taking advantage of the eel's swallowing and greedy nature, live bait is mixed with compound feed for feeding training. The eel's start feeding time, peak feeding time and finishing time are required to be mastered to facilitate artificial feeding training.

(1) Before training, the eels must be starved for 1-2 days without being fed any food.

(2) Before starting to train the eels, feed them with live bait that accounts for about 1% of their weight for 2-3 days, such as river frogs, earthworms, mealworms, etc., and the "four determinations" must be achieved.

(3) After stopping feeding for another 1-2 days, make the compound feed and live bait into a "cake" style, that is, cut part of the live bait into pieces and mix it with the compound feed, and stick part of it to the outside, or use a dough press to press it into thin strips for feeding. The total amount is about 1% of the weight of the stocked eels. On the first day, it is 80% live bait and 20% compound feed, on the 2nd-3rd day, it is 60% live bait and 40% compound feed, on the 4th-5th day, it is 40% live bait and 60% compound feed, and so on. Generally, it will take 7-10 days for the eels to be fully tamed and eat artificial compound feed.

(4) During the feeding process, observe the leftover food, water quality and excrement every day to judge the feeding situation of the eel. If the feeding is abnormal, remove the leftover bait and reduce the proportion of compound feed or appropriately reduce the feeding amount. If the eel still cannot eat normally, stop feeding for 1-2 days and then continue. If the eel can finish eating, gradually increase the proportion of compound feed until the feeding is successfully trained. After the feeding is successfully trained, immediately mix drugs into the compound feed to kill parasites. For the eels that have been successfully trained, make the compound feed into dry granules the size of mung beans or peas and feed them. The total amount should also be gradually increased to 2%-10% of the eel weight, and then enter the daily management work.

7. Summer Shade

The still water soilless breeding pond for yellow eel is small (15-20m2), with shallow water level (about 15-20cm), and the water temperature can easily exceed 30℃ in summer. Shading is an essential step to avoid the heat. Generally, a shade net is set up on the pond, and climbing plants such as grapes, loofah, trichosanthes, and pumpkins are planted by the pond. But pay attention to leaving 10% to 30% of light on the surface of the pond. At the same time, when the temperature exceeds 33℃, the water level in the pond should be deepened to reduce the density of yellow eels, and new water should be slowly injected. Groundwater can be used to adjust the water temperature of the eel pond.

8. Water quality control

The pH value, transparency, dissolved oxygen, ammonia nitrogen, temperature, nitrite and sulfide of the aquaculture water are the main ecological factors that induce fish diseases besides pathogens. To maintain good water quality in the eel pond, the following points are generally required:

(1) Drug control. Every 10 to 15 days, use 10g/m3 of quicklime or 1g/m3 of bleaching powder to spray the whole pond. In the north, the water quality is alkaline, so bleaching powder should be used more often; in the south, the water quality is acidic, so quicklime can be used more often. Mix oxytetracycline, sulfonamides and other drugs into feed for oral administration. Each drug should be used for 3 to 5 days, and then used alternately every 20 to 30 days.

(2) Maintain a suitable water level. If the water level is too deep, the water temperature will drop, and the water quality will not be easy to improve. In addition, the eel needs to stick its head out of the water frequently to eat and breathe. To reduce the eel's physical consumption, the water level should be shallow. However, if the water level is too shallow, the water temperature will change dramatically, and the eel's activity space will be small, which is extremely unfavorable for the eel's growth and development. The general water level is 15-20 cm, and it can be deepened to 30 cm when the temperature is high. The water level may also change under special circumstances. For example, the water level in the seedling pond, the pond for sale, and the sick eel pond should be shallow, while the water level in the adult eel breeding pond can be deeper. If the aquatic plants grow luxuriantly, it is sufficient to change the water once a month. Generally, fresh water should be added in time according to the amount of water evaporation, but the leftover food on the feeding table should be cleaned every day to avoid deteriorating the water quality. When changing the water, the temperature difference between the inlet water and the water in the pond should be controlled. The temperature of small eels should not exceed 2°C, and that of large eels should not exceed 5°C. The daily temperature difference of the water temperature should be less than 10°C. It is best to build a reservoir to facilitate water changes.

(3) Maintain biodiversity. Eel ponds should be stocked with golden apple snails, field snails, small fish, loaches, etc. to remove residual bait and regulate water quality. Many organisms are also indicators of water quality. However, it is important to maintain a reasonable proportion of these organisms in terms of quantity. Generally, the food intake (dry weight) of yellow eels is 1% to 2% of their body weight, and the dry weight of fish feces is 2% to 10% of their food intake. Generally, the stocking density of eels does not exceed 3kg/m2. Calculated based on the dry food intake of loaches being 2% to 4% of their body weight, the number of loaches stocked per m2 of eel pond should not exceed 0.3kg. Loaches should be stocked after yellow eels have been tamed and fed with compound feed, so that they can fully play the role of eating yellow eel feces and preventing yellow eels from "fevering". Stocking toads is particularly effective in preventing the yellow eel's unique plum spot disease. Generally, 1 to 2 toads can be stocked in each small pond. The stocking density of snails should not exceed 0.25kg/m2. In addition, appropriate amount of green algae can be cultivated and photosynthetic bacteria (PSB) can be added.

Observing the water color is the key to regulating water quality. Generally, yellow-green, blue and clear water is good. Brown, gray or black water is abnormal and remedial measures should be taken in time.

IX. Diseases and prevention of eel farming

Disease prevention and treatment of eels The eels have relatively strong disease resistance and rarely get sick during artificial breeding. However, if they are poorly managed or the environmental factors are seriously adverse, their growth rate and survival rate may be affected.

Farming technology

1. Operation procedures of still water and soilless ecological breeding technology for yellow eel

There is a lot of content in the still water and soilless ecological breeding technology of rice field eels. The key technologies include shallow water semi-artificial breeding technology of rice field eels, compound feed domestication technology, and pest and disease control technology. Among them, eel species screening and processing are the key to the success of rice field eel breeding.

2. Construction and treatment of eel ponds

The construction of eel ponds should take into account the following five design principles: simulate the natural environment; convenient drainage and irrigation, conducive to heat preservation; conducive to taming and feeding compound feed; conducive to the prevention and control of eel diseases and pests; escape prevention, easy capture and convenient management. The area of ​​outdoor static water soilless breeding ponds is 15-20m2, and the indoor breeding area is smaller, generally 6-10 m2. Pool wall height: 20-30cm indoors, 40-50cm outdoors. The wall can be built with a single brick, cement is applied inside, and the top of the wall is horizontally built with bricks in a "T" shape. Plastic film pools can also be used for breeding. Several small pools of the same specifications are strung together in a row, but the inlet and outlet are independent to prevent diseases and pests from spreading to each other. The shape of the fish pond is preferably rectangular or square. The outlet is slightly lower than the bottom of the pool to ensure thorough sewage discharge; the water inlet is set just above the food table, opposite to the outlet, and the position should be high, generally 15-20cm from the bottom of the pool; the overflow outlet is 25cm from the bottom of the pool, and the overflow outlet is not required for indoor breeding. The diameter of each water outlet is about 5-6cm and should be covered with a nylon net to facilitate the discharge of feces and prevent the eels from escaping.

After the cement pool is built, it must be de-alkali treated. Using a new pool without de-alkali treatment is one of the main reasons for the failure of many farmers. The method is: soak it with phosphate fertilizer (1 kg of phosphate fertilizer for 1 ton of water) or acetic acid for a week, drain the soaking water and replace it with clean water; or fill it with water and soak it for 30 days (it is best to put grass piles to ferment), and then drain it. Plastic film pools do not need to be de-alkali treated.

Fish nests are very important in static water and soilless culture. Various pipes, bamboo tubes, brick gaps, water plants, etc. can be used as fish nests. Since eels have a certain degree of aggregation, the area of ​​the fish nest should not be too small. The general principle of setting up eel nests is: it is convenient for eels to enter and exit freely, the interior is dark and lightless, and there is enough space. In production, it is generally better to use waste bicycle tires disinfected with potassium permanganate solution as eel nests. The tires are placed under the water plants, and 5-6 tires can be placed in each small pool. Bamboo tubes of about 2m can be used. The size of the hole depends on the eel body. It is appropriate to be larger than the eel. Every two bamboo tubes are in a row, and each pool has 3-5 rows, with a spacing of about 0.3m between each row. Bricks are placed under each row of bamboo nests to make a large space under the bamboo nests, which is convenient for water flow and sewage discharge. In order to fix the bamboo nests, it is best to press bricks above the hole, which also plays a role in shading and shading.

3. Aquatic Plant Stocking

"To raise fish, you must first raise water, and to raise water, you must first raise grass." The placement of aquatic plants is one of the key technologies for static water soilless aquaculture. Reasonable placement of aquatic plants to purify water quality can reduce the number of water changes in the eel pond to once a month, saving water and labor, and can prevent heatstroke, reduce stress reactions, provide fish nests, and prevent diseases and insect pests. Aquatic plants are selected according to the standards of "preventing fish from escaping, growing fast, purifying water quality, and facilitating fish hiding." Common ones include water peanuts, water hyacinths, water lilies, and fine green duckweed. The planting area of ​​aquatic plants should not exceed 2/3 of the total pond area. At least 1/3 of the fish pond area should be left empty to set up a feeding table and facilitate the activities of yellow eels. In different seasons, aquatic plants should be reasonably matched in a certain proportion. In summer, water hyacinths and water lilies are the main ones, while in spring and autumn, water peanuts and fine green duckweed are the main ones. In winter, no aquatic plants are left to prevent yellow eels from freezing under the aquatic plants. Generally, aquatic plants are put in 15 days before stocking eels. Before putting in, they should be disinfected by soaking in 100g/m3 potassium permanganate solution for 0.5h, or by soaking in 10g/m3 copper sulfate solution for insecticide.

In daily management, excess aquatic plants should be removed in time or overly long aquatic plants should be cut. In combination with eel pond disinfection, 10g/m3 quicklime or 0.7g/m3 copper sulfate solution should be sprinkled on the grass to prevent aquatic plant pathogen infection.

4. Eel species selection

The key to successful eel farming is the quality of seedlings. At present, the large-scale breeding technology of eels has not yet been mastered, and the seedlings used in production are basically from wild resources. There are many ways to catch wild eels, including cage catching, hook fishing, electric shock, shovel digging, clamp catching, net lifting and drug catching. Some wild eels have been transferred and stored and transported many times, and some wild eels themselves carry diseases and insect pests. Therefore, the quality of wild eel seedlings purchased from the market is uneven, and strict screening is very important in production.

There are many methods for screening eel seedlings. The sensory screening method (based on body color, external injuries, strength, mucus, etc.), water flow screening method, behavioral screening method, and burrowing screening method are highly subjective and cannot screen eels with latent diseases in the body. It is also rather troublesome to screen them one by one. The drug immersion method is highly irritating to eels, the drug concentration is difficult to control, and the operation is rather troublesome. The feeding screening method has a better screening effect, but there are no reports on its specific operation process and quantitative method.

The eel selection method we use in production is: put the eel seedlings in a plastic container in shallow water at a certain density, soak them in medicine, feed them a fixed amount of empty mealworm larvae for 5 consecutive days, change the water once every morning, and check the eel's food intake. In the range of 18-30℃, if the average daily food intake of the eel exceeds 0.5% of the eel's body weight, then keep the seedlings; if the average daily food intake of the eel is less than 0.5% of the eel's body weight, then eliminate the seedlings. The eel stocking time is generally 10-15 days after the water plants are released.

5. Semi-artificial breeding technology of yellow eel

The semi-artificial breeding technology of the yellow eel has the advantages of high fertilization rate and hatching rate, concentrated breeding time, convenient management and high efficiency, and is an inevitable trend for the large-scale breeding of yellow eels. The breeding pond is designed and built according to the requirements of static water soilless breeding, with an area of ​​20-30m2. The types of aquatic plants vary from place to place, including water hyacinth (Eichhornia Crassipes Solm.), water peanut (Alternanthera Philoxeroides Griseb), water lily (Pistia stratiotes), and goldfish algae (Ceratophyllum demersum). From March to July each year, 10 parent eels are stocked per square meter of the breeding pond (female: male ratio is 6:4). The management method is the same as static water soilless ecological breeding, but the number of water changes is increased during the breeding season (May to August), that is, the water is changed once every 7 days, the water depth is 20-25cm, and the pH is 6.0-8.5. After the yellow eel lays eggs, it is promptly fished out for artificial incubation, and the unfertilized eggs should be removed in time. The method of drip incubation is: the incubator is a shallow dish of 40cm×40cm×7cm, with 2cm thick disinfected river sand at the bottom, the water drips in from the container at a high place, overflows from the side wall of the dish, the water depth remains about 5cm, and the daily temperature difference does not exceed 2℃. When the fertilized egg just enters the incubator, the number of water drops is 10 drops/min, lasting for 24 hours, and gradually increase the water drop speed until the seedlings are hatched.

6. Eel food

Eels have strict selectivity for food, and it is difficult to change their food after adapting to a certain food. At present, artificially cultivated eel species mainly come from wild eels that feed live bait. If you simply feed live bait when raising eels, it is not conducive to the healthy growth of eels, and it increases the investment cost. It may be restricted by the fact that feed resources cannot be owned for a long time. If feeding compound feed or adding a small amount of live bait into compound feed, it is possible to effectively reduce the cost of feed, ensure comprehensive nutrition, facilitate the addition of additives and drugs, and prevent and control diseases and diseases. Therefore, feeding compound feed is an important measure to develop the eel breeding industry.

1. Conditions for domestication

(1) The feeder must be patient and the food-drying process should take at least 7-10 days. It is normal for the food-drying process to be successful in 10-30 days.

(2) The area of ​​the eel pond should be small, generally 15-20m2. Eel feeding is a comprehensive use of the sense of smell, taste and sideline system. It must be within an effective range before eels can discover and prey on food.

(3) Domestic food should be based on the four certainty that eel feeding can be "fixed point, timed, fixed quality and quantitative".

(4) Domestic food should be determined according to the season, weather and the specifications of the eel species. For example, eels are very conducive to domestic food when hibernation is just over, the temperature rises, and the start of feeding.

(5) If it is a wild eel species, leeches should be carefully screened and killed, and then stabilized for a period of time to eat.

(6) It is not advisable to stock loaches and other fish before domestication. Putting them in too early will cause scrambling with eels and will be unfavorable to domestication.

2. How to eat

Taking advantage of the characteristics of eels' swallowing and gluttony, mix live bait with compound feed for food and food. You must master the time for eels' start feeding, peak feeding time and time for eating, so as to facilitate artificial food training.

(1) Before eating, the eels should be hungry for 1-2 days and do not feed them.

(2) Before starting to eat, feed live bait with about 1% of the weight of the eel for 2-3 days, such as river frogs, earthworms, mealworms, etc., and achieve the "four fixed".

(3) After stop feeding for 1-2 days, the compound feed and live bait are made into a "cake" type, that is, some live bait is cut and crushed together with the compound feed, and partly stick to the periphery, or press it into thin strips with a dough press. The total amount is about 1% of the weight of the stocked eels. On the first day, it is 20% of the compound feed of 80% live bait, on the second and third days, it is 60% live bait and 40% compound feed, on the 4-5 days, it is 40% live bait and 60% compound feed, and so on. Generally, it can be completely domesticated and eaten in 7-10 days.

(4) During the food-drying process, observe the residual food, water quality and discharged feces every day to judge the feeding situation of the eel. If the food intake is not normal, take out the residual bait and reduce the proportion of compound feed or appropriately reduce the feeding amount. In this way, if the feeding is still not normal, stop feeding for 1-2 days before continuing. If the eel can be eaten, gradually increase the proportion of compound feed until the food is successful. After the food is successful, immediately mix medicine in the compound feed to kill parasites. For eels after the food is successful, feed the feed into dried pellets as large as mung beans or peas for feeding. The total amount should also be gradually increased to 2%-10% of the eel weight, and then enter daily management work.

7. Summer and shade

The eels are small in still water and soilless aquaculture pool (15-20m2), and the water level is shallow (about 15-20cm), and the water temperature is very likely to exceed 30℃ in summer. Shading and summer escape is an indispensable link. Generally, you should set up a shade net on the pond, and plant grapes, loofah, squash and other climbing plants such as grapes, loofah, squash, and pumpkins by the pond. However, please note that there should be 10%-30% light on the water surface of the pond. At the same time, when the temperature exceeds 33℃, the water level in the pond should be deepened, the density of eels should be reduced, and fresh water should be slowly injected. Groundwater can be used to adjust the water temperature of the eel pond.

8. Water quality control

The pH value, transparency, dissolved oxygen, ammonia nitrogen, temperature, nitrite and sulfide of aquaculture water are the main ecological factors that induce fish diseases other than pathogens. To maintain good water quality in the eel pond, the following are generally required:

(1) Drug regulation. Water bodies are sprinkled with 10g/m3 quicklime or bleach powder every 10~15 days, and the water quality in the north is alkaline, and the bleach powder is used more often; the water quality in the south is acidic, and the quicklime can be used more often. Mix the oleracin, sulfonamide and other drugs into the feed and take them internally. Each medicine is used for 3~5 days, and cross-use once every 20~30 days.

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(3) Maintain biodiversity. Eel ponds should be stocked with snails, field snails, small fish, loaches, etc. to remove residual baits to regulate water quality. Many organisms are also indicators of good or bad water quality. But pay attention to the reasonable proportional relationship between these organisms. Generally, the feeding amount (dry weight) of eels is 1% to 2% to 2% of their weight, and the dry weight of fish manure is 2% to 10% of the feeding amount. Generally, the stocking density of eels does not exceed 3kg/m2. Calculated as the dry feeding amount of loaches is 2% to 4% of their weight, then the loaches should not exceed 0.3kg per m2 eel pond. Loaches should be stocked after feeding with feed, so that the role of loaches eating eels can be fully utilized to prevent the unique plum blossom spot disease of eels. Generally, 1 to 2 cans should be placed in each small pond. The stocking density of field snails should not exceed 0.25kg/m2. In addition, an appropriate amount of green algae can be cultivated and photosynthetic bacteria (PSB) can be added.

Observing the water color is the key to regulating water quality. Generally, yellow-green, blue and clear-headed are better. If the water color is tea brown, gray or black, it is abnormal. Remedial measures should be taken in time.

9. Diseases and prevention of eel farming

The disease prevention and treatment of eels have relatively strong resistance to disease prevention and treatment. They are generally rarely affected during artificial breeding. However, if they are poorly managed or have serious environmental factors, they may affect their growth rate and survival rate.