Detailed Explanation of Ecological Breeding Techniques for Rice Field Eel Farming

1. Ripening and spawning induction of parent eels: After late May, when the water temperature reaches 25°C, each parent eel is first injected with LRH-A (luteinizing hormone-releasing hormone) 12.5 micrograms, injection volume 0.5 milliliters, to ripen the gonads; 7 days later, inject DOM (domperidone) 0.5 micrograms, injection volume 0.5 milliliters, or LRH-A + HCG (luteinizing hormone-releasing hormone + human chorionic gonadotropin) 0.5 micrograms + 3 international units, injection volume 0.5 milliliters, to induce spawning, then place the parent eels into the breeding pond.

2. Stocking of parent eels: The stocking density should preferably be 1 to 2 pairs of parent eels per sq m; the density must not be too high. 3. Feeding and management of parent eels: After the parent eels are put into the pond, the water level can be appropriately raised and kept at about 50 cm to prevent a sharp rise in water temperature during the day, which is unfavorable to the gonadal development of rice field eels. Generally, no food is given for the first 2 days; from the 3rd day onward, feed a small amount of earthworms to facilitate food attraction, and then artificial feed (the feed used during production farming) can be given. Place the feeding tray beside the water inlet so that the scent of the feed spreads throughout the pond with the water flow to attract the parent eels to feed; continue this for several days until feeding becomes normal. The breeding pond should preferably have a slight water flow to keep the water quality fresh, so that the rice field eels remain in good water quality and water temperature. The water inlet should be filtered with 40-mesh silk gauze to prevent the entry of harmful organisms. 4. Management during the spawning period: Pay close attention to whether bubble nests appear in the breeding pond. Once a bubble nest forms, it indicates that the female eel will spawn in about another 3 days. During this period, the environment should be kept quiet and feeding reduced. During this period, 2 rice field eels can be seen poking their heads out of the burrow entrance to breathe. If another male eel approaches, the original male eel in the burrow will launch a sudden attack; generally the intruder will retreat without further attack. If only 1 rice field eel is seen poking its head out of the burrow entrance to breathe, it proves that the female eel has finished spawning and left, leaving only the male eel to guard. Experiments show that the fertilization rate of this ecological breeding can reach more than 85%. 5. Incubation management of fertilized eggs: Once a foam nest with fertilized eggs is found in the breeding pond, the young eels will generally hatch after 5 to 7 days. At this time, the incubation water temperature should be kept at 25 to 28°C. Some aquatic plants should be appropriately placed in the incubation pond to provide hiding and resting places for the young eels and to facilitate their collection later. Experiments show that the natural hatching rate can reach 80%. 6. Harvesting and rearing of the eels: Within 5 days after hatching, the eels can be scooped out and transferred to the eel fry rearing pond for culture. The water temperature in the eel fry rearing pond should be the same as that in the incubation pond (difference not exceeding 2°C). When scooping the fry, use a small net bag made of fine gauze, and the action should be quick to avoid affecting fry collection because of attacks by the guarding male parent eels. The collected eel fry are put into a dedicated pond for rearing. One week after hatching, after the yolk sac disappears, some cooked egg yolk or water fleas can be fed, and later tubifex, fly maggots, and chopped earthworms, snails, and mussel meat, etc. can be fed. Parent eels that have already spawned should also be carefully reared, and after about 15 to 20 days they can spawn a second time.