Hezhuang is a remarkable example of goldfish culture, known for its elegant appearance and lively behavior. Its silver-white scales shimmer beautifully, while the red head crest adds a striking contrast, creating a vibrant and eye-catching look. The fish moves gracefully, resembling cranes in flight, making it a popular choice among aquarists.
**1. Breeding Stock Preparation**
Breeding begins in March each year. Female fish selected are typically 2-3 years old, while males are 1-2 years old, with a male-to-female ratio of 1:1.2. Only those with a bright, well-formed red head crest are chosen, while irregular colors like yellow or white are usually excluded. Stocking density is lower than for commercial fish, and feeding increases gradually as temperatures rise. It generally takes about one month for the gonads to mature.
**2. Selection of Broodstock**
In early April, breeders check the gonads in the breeding pond. Females should have a soft, elastic belly and an oval body shape, while males should be robust with full, flowing fins. For females, a micro-infrared method is used to confirm maturity, and for males, visual signs such as active chasing behavior are observed.
**3. Artificial Insemination**
Artificial insemination is usually performed in mid-April when water temperature reaches around 25°C. A disposable pectoral fin injection method is used. For every 100g of female, 1-2 μg of LHRH-A2 is injected, and males receive half that dose. The best time for injection is around midnight, and the fish are left to rest for 18–20 hours.
**4. Artificial Insemination and Hatching**
In the evening, when males begin aggressively pursuing females, both are quickly transferred into a container filled with water. The eggs are gently extracted by squeezing the abdomen, releasing milky white mucus or yellow eggs. One person holds the female’s head and body, while another gently presses the abdomen to release the eggs into a sterile basin containing 25°C normal saline. Males are then processed similarly, and their sperm is mixed with the eggs using a feather. The fertilized eggs are then placed in the hatching tank.
During incubation, clean, oxygen-rich water with a pH of 7.5–8.0 is essential. At 25°C, the eggs hatch within 3–4 days. Daily treatment with 10ppm malachite green helps prevent fungal infections, and regular water changes are necessary.
**Seedling Rearing**
Freshly hatched larvae rely on their yolk sacs for nutrition. After four days, they are fed cooked egg yolk through a 25# plankton net, ensuring even distribution in the water. Feeding once daily, with food consumed within 1–1.5 hours, ensures proper growth. By day 8, the fry grow to over 1cm, showing improved swimming ability and beginning to feed on small plankton. At 3cm, they are ready for more advanced feed, and weekly water changes help maintain health.
**Advantages of Artificial Insemination**
Artificial insemination significantly reduces the physical stress and energy expenditure of broodstock during mating, leading to higher survival rates. Studies show that post-mating survival rates can increase from 50%–75% with natural mating to over 95% with artificial methods. Fertilization rates also improve dramatically, rising from under 40% naturally to over 80% with artificial techniques. Additionally, this method helps maintain genetic purity.
**Important Notes**
Fish nests should be suspended in the upper to middle layers of the water, with weights added on either side. They should be kept fully submerged in the hatching pool. If exposed to air, the eggs may dry out and sink, leading to suffocation. During incubation, especially in the first three days, avoid turning the eggs unnecessarily, as this can lower hatching success and increase the risk of deformities.
(Southwest Agricultural University, Department of Fisheries – Yu Xiaodong)
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