Carp is the most widely distributed and highest-yielding freshwater fish in China, making it a key species for aquaculture. Autumn is an ideal time to use family-owned aquaculture ponds to breed eel fry. This practice can help meet the needs of spring stocking, shorten the breeding cycle, and boost overall production. The following are the techniques for artificial propagation of eel fry in autumn:
First, selecting the right broodstock is crucial. Choose mature fish weighing over 500 grams. Female eels should have a swollen, soft belly, with redness and swelling around the anal and genital openings, along with signs of congestion. Male eels, when gently pressed, should release white milt, and their anal area should not be swollen.
Second, the ratio of males to females should be carefully maintained at 1:5 to 1:7. Adding more males can accelerate the spawning process of the females, improving efficiency.
Third, for spawning, place the male and female eels into a fish bowl filled with water and provide a suitable spawning nest. Position the fish so that their backs are about 3 cm below the water surface. This temperature difference and gentle water flow can stimulate spawning. To enhance the effect, inject 2 ml of 50% glucose solution at the base of each pectoral fin of the female eel.
Fourth, during incubation, ensure the water in both the spawning and hatching pools is not too rich or turbid, as this can cause floating heads and prevent proper spawning. Use clean, fresh water with good water flow, and maintain a temperature between 18-22°C. Oxygenation can be achieved using fibrous roots, avoiding materials like daffodils or other plants that may stick to the eggs or cause sunburn.
Fifth, to increase fertility and control spawning timing, artificial aphrodisiacs can be used. During the breeding season, inject 3–5 ml of 50% glucose solution into the base of the female’s pectoral fin at a 45-degree angle, depending on her size. After injection, place the female in the spawning pool and pair her with two male eels. The spawning pool should be kept in a well-circulated environment. Spawning usually occurs 10–15 hours after injection, and egg production increases by approximately 40% compared to natural spawning.
The eggs are adhesive, so they need to be placed on a suitable substrate. Use aquatic plants or sessile narcissus roots to create a nest. Once the eggs are attached, move the nests into a cleared area where young fish larvae are already present, ensuring optimal conditions for hatching and early development.
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