Eel is loved by people for its tender meat, delicious taste and extremely high nutritional value. Together with "eel and loach", it is called the "three freshwater ginseng". At present, eels are mainly captured from nature, which cannot meet people's needs. The most critical problem in artificial breeding of eels is the difficulty in source of seeds. Therefore, artificial propagation and seed cultivation of eels are particularly important.

1. Selection and cultivation of brood eels

The brood eels currently used for breeding are fished from reservoirs and lakes using eel cages, traps and other fishing tools. Due to the unique sex reversal phenomenon in eels, it is difficult to 100% distinguish between males and females. Generally, the male body length should be above 40cm, with the best around 50cm, and the female body length should be around 25cm. To be a pro-eel, you need to be fat and strong, with a bright yellow body color, an enlarged and soft lower abdomen, an obvious outline of the ovaries, a light orange-red abdomen, and red and swollen genital pores.

Female and male parent eels are cultivated separately at a ratio of 2:1 or 3:1. After the parent eel pond is cleaned and disinfected, 20-25 parent eels are released per square meter. After artificially taming silkworm pupae and other animal baits, during the cultivation period, attention should be paid to frequently infusing new water, adjusting the water quality, and keeping the water depth at 10-25cm. The water should be changed twice a week, 1/3 of the water each time, to ensure long-term growth. Time microfluidic water is beneficial to stimulate the normal development of gonads.

2. Induction of labor and hatching

1. Aphrodisiac spawning: When the water temperature reaches 25-28 degrees Celsius, chorionic gonadotropin solution is injected to induce labor, and each female eel is injected with 400 -500 international units (iv), half for male eels. Intraperitoneal injection has better effect and shorter effect time.

After the eels are injected with drugs, the male and female eels are mixed in a ratio of 2:1 or 3:1 and placed in the spawning tank. After 45-50 hours, the eggs can be produced by themselves or squeezed out artificially. During insemination, the eggs of the female eel are usually collected first (eggs are squeezed or taken by cesarean section), and then the male eel is dissected to remove the semen, and dry insemination is used.

2. Incubation management: The optimal water temperature for incubation is 22-28 degrees Celsius. Within the optimal range, the higher the temperature, the higher the hatching rate. Generally, at 25 degrees Celsius, it takes 150 hours (7- 8 days) to hatch. The total length of newly hatched eel seedlings is 12-20mm. 3-4 days after hatching, the eel seedlings can be placed in the nursery pond for special cultivation. At this time, the temperature difference between the two water temperatures should not exceed 3-5 degrees Celsius.

3. Seedling cultivation:

Put the eel seedlings into the nursery pond. After the yolk sac gradually disappears (about 1 week), start feeding zooplankton (cladocerans). , copepods and some large rotifers), and then use cooked egg yolks and soybean powder to make a paste for feeding. You can also use clam meat, earthworms, various animal blood and scraps to make a paste and spread it evenly into the pool every day. Feed 4-6 times, and the daily feeding amount accounts for 2-5% of the fish body weight. If the stocking amount is 450-500 eels/m2, you can harvest 20-40 eel/kg standard eels in winter.

4. Water quality adjustment

Although eel seedlings are highly resistant to sewage, hypoxia, and disease, in high-density intensive breeding, water quality adjustment must be paid attention to every week. Inject water or change the water once, and each water change accounts for 1/3 of the total pool water. In midsummer, mushrooms, wild rice, water peanuts or turnips can be planted in the nursery pool to provide shade. A small amount of loach seedlings can also be put into the pond with a density of 30-50 fish/m2, which can effectively remove residual food, control water quality, and prevent young eels from wandering around.

5. Prevention and treatment of eel disease

To prevent eel disease, clean and disinfect the pond before the eel seedlings enter the pond, and bathe the eel seedlings with 3-4% salt water. 2-5 minutes, generally young eels have few diseases.

Saprolegnia, also called skin mold, is caused by wounds being infected by saprolegnia when young eels bite each other or are invaded by harmful organisms. Once infected with saprolegnia, a layer of white hair will appear on the surface of the body, commonly known as "hair growth" or "white hair disease". The diseased eel will show signs of irritability, rotten muscles in the affected area, loss of appetite, and eventually become emaciated and die. Eggs infected with Saprolegnia will also cause mass death of eggs.

Prevention and control methods:

1. Use 400g each of table salt and nahc03 per cubic meter of water, and pour the water into the entire pond for three days.

2. Soak eel eggs in 0.7ppm malachite green solution for 10-15 minutes and use for three consecutive days.