Artificial Fattening and Fry Breeding Techniques in Rice Field Eel (Monopterus albus) Farming

Methods for artificial fattening of rice field eels:

Rice field eel farming ponds should be built in wind-sheltered, sunny locations with a guaranteed water source and relatively solid soil. Cement ponds, earthen ponds, and rice field culture are all acceptable. The pond area for farming rice field eels depends on the scale of farming, generally 20-100 sq m is suitable, with a pond depth of 70 cm, and the pond walls should extend about 30 cm above the water surface to prevent the eels from escaping.

The pond shape is best as a long oval, with the pond perimeter built of bricks, and the top of the pond side walls made into a “t” shape with an overhang of about 20 cm. The pond bottom is paved with cement, and then about 25 cm of pond mud is spread on top, to facilitate the eels burrowing and hiding. The cement in the pond should not be too deep, preferably maintained at about 15 cm. The drainage holes should be equipped with low-lying escape-proof ponds and old nylon mesh. One-third of the pond water surface area should be planted with aquatic plants such as water hyacinth, to serve as shade and hiding habitat for the rice field eels. The seedlings are best sourced from artificially bred and domesticated superior dark-yellow large-spotted rice field eels. The eel fry are required to be mainly wild, selecting seedlings with no body damage, no parasites, strong physique, and uniform size, 60-80 per kg, with about 1 kg of rice field eel fry stocked per sq m. For fry of 20-30 per kg, the stocking density is 3-4 kg/sq m; for fry of 10-20 per kg, the stocking density is 4-6 kg/sq m. Fry of different sizes should be raised in separate ponds, and at the same time a small amount of loach should be added at a ratio of 10%. Feeding management.

1. Feed feeding: Rice field eel feed can be earthworms, river clam meat, snail meat, small miscellaneous fish, small tadpoles, small insects, animal offal, and fruits and vegetables, etc. Rice field eels hide by day and come out at night. Within one week after stocking the seedlings, feeding is generally done after dark in the afternoon, then the feeding time is gradually moved earlier, domesticated to the fullest extent to feeding at 2 pm; the feeding rate for fresh bait is 5%-6%, and the feeding rate for dry bait is 1%-2%, and increase or decrease as appropriate according to water temperature. The animal-based bait to be fed must be fresh

2. Daily management: mainly to keep the water quality “fertile, lively, tender, and refreshing.” When the seedlings are just stocked, the pond water should be shallower, preferably 10 cm, and then gradually deepened, generally maintained at 15-20 cm. The water should be changed frequently, once every 3 days, with 1/2 of the water changed each time. During high temperatures in summer, change the water once a day, and the best time to change the water is in the early morning, when the temperature of the water source is basically consistent with the temperature of the pond water, to prevent the rice field eels from getting a “cold” due to too large a temperature difference (greater than 3 degrees). Every morning, promptly remove dead eels, diseased eels, and weak eels. Vine plants such as loofah and grapes can be planted along the pond edge for shade and cooling.

For new fish, select eel species for breeding. For female eels, it is advisable to select eel species with a body length of more than 35 cm, a weight of 50—150 g, an enlarged abdomen with a transparent band, and red and swollen genital pores; those with egg grains are best. For male eels, it is advisable to select eel species with a length of more than 55 cm, a weight of more than 150 g, blood-streak markings on the ventral surface, a transparent fluid that can flow out when the abdomen is squeezed, and sperm visible under a microscope. It is advisable to pair 2—3 female eels with 1 male eel.

For induced spawning and breeding, measures such as aeration, increasing the water exchange volume, adjusting the breeding density, and providing high-quality bait can be used to naturally induce spawning in the brood eels and improve their reproductive capacity. A one-time injection of lrh—a can also be given, with female eels injected with 10 micrograms per 50 g of body weight, and male eels injected with 15—25 mg per eel. Male eels should be given the thoracic injection 24 hours earlier than female eels. During injection, the depth should not exceed 0.5 cm, and the injection volume should not exceed 1 ml, for the best induced spawning effect.

For artificial insemination, hold the front part of the female eel with one hand using a towel, and squeeze the abdomen backward with the other hand. If the cloaca is blocked, it can be cut open, and then the eggs can be squeezed out. The squeezed eggs are placed in a disinfected jar or basin. Kill the selected male eel, cut the testis into pieces and grind them fine, wrap the minced testis with a 100-mesh sieve, squeeze the semen into the egg-containing container, stir thoroughly for 5 minutes, wash away the testis residue and blood stains with clean water, and place the fertilized eggs in a temperature-controlled incubator or indoors for incubation. Regardless of the number of eggs, at least 2 or more male eels should be used for insemination.

For temperature-controlled incubation, the incubation water depth is preferably about 10 cm, and the water should be changed frequently during the process, but the temperature difference must not exceed 4 degrees C. The higher the water temperature, the shorter the time required for incubation.

For fry rearing, cement ponds are preferable, with a small amount of manure fertilizer water appropriately applied in the pond for the reproduction of tubifex worms, and aquatic plants such as water hyacinth stocked on the water surface. The fry stocking density is about 200 per sq m. After 1—2 months, when the eel fry grow to about 10 cm, they can be moved to adult eel ponds for rearing.