I. Preparation for Breeding Conditions
1. Selection and Cultivation of Broodstock
As autumn begins, select goldfish aged 1 to 3 years that meet species standards in terms of body shape, swimming posture, and overall health. These fish should be kept in cement pools or pots. Since goldfish do not show clear non-breeding signs, the male-to-female ratio is not a major concern at this stage.
Stock the selected broodstock in a culture area ranging from 2 to 10 square meters. This allows sufficient space for movement, promoting both health and comfort. Maintain a stocking density of 5 to 10 fish per square meter. The pool must have good drainage, with water depth between 25 to 40 cm depending on fish size. Aeration and oxygenation equipment are essential to maintain water quality.
Feed the broodstock high-protein, low-fat food 2 to 3 times daily. Each feeding should last about 8 to 10 minutes, ensuring they eat everything without overfeeding. Include floating pellets and live bait like leeches or red worms to support gonad development and overall growth.
Maintain clean and lively water, ideally with a light green tint. If the water becomes too rich, adjust it by partial water changes. If the water turns old (dark brown or green with suspended particles), consider changing the water or turning the pond. During nighttime or rainy weather, use an air pump to supplement oxygen levels.
2. Spawning Pool Preparation
Prepare a spawning pool of 1 to 5 square meters with a depth of 40 cm. It can be a smooth cement pool or a large pot. After cleaning and disinfecting, fill the pool with 25 cm of water and let it sit for 2 to 3 days before introducing the broodstock. Cover the pool with plastic film to raise the temperature and equip it with an aeration system.
II. Breeding Process
Breeding typically occurs during autumn and winter. When the water temperature drops to 15°C, cover the breeding pond with plastic film or move the broodstock indoors to increase the temperature. Once the temperature rises above 20°C, breeding can begin. The key to this technique lies in controlling temperature shifts—cold stimulation helps synchronize the fish’s reproductive cycle, while a temperature rise triggers spawning.
1. Selection of Broodstock
The selection criteria for breeding stock are similar to those for reserve broodstock, but gender identification is easier. Transfer the selected fish into the prepared spawning pond at a ratio of 1:1.5 to 2 males to females. Alternatively, inject them with oxytocin to stimulate spawning.
2. Drug Injection
Use 0.65% physiological saline as a solvent. Administer a solution containing LRH-A at 25 micrograms and HCG at 500 units/ml. Inject 1 ml per female weighing 250 grams. Males receive half the dose. Inject the solution from the base of the pectoral fin into the abdominal cavity. A single injection is common, though a two-step approach (first LRH-A, then HCG after 12 hours) may yield better results.
3. Preparing the Spawning Nest
Once the broodstock is placed in the spawning pool, immediately install a spawning nest. Use materials such as goldfish plants, water hyacinth, brown silk, willow roots, wool, or plastic ropes. Ensure the nest is thoroughly disinfected, soft, finely branched, and not too loose to avoid damaging the fish.
III. Hatching Process
After drug injection, goldfish typically spawn within 12 to 24 hours. If the water temperature exceeds 22°C, females can release fully mature eggs within 24 hours. Inspect the nests the following day and remove attached eggs. Soak them in a 20 mg/l methylene blue solution for 15 minutes before transferring them to hatching ponds.
The hatching tank should be indoors or covered with plastic to maintain a temperature above 20°C, ideally around 25°C. A cement pool of 5 to 10 square meters is ideal, as it also serves as a fry culture area. Avoid small tanks, which are prone to rapid temperature and water quality fluctuations, and large tanks, which may affect fry development. Disinfect the hatching pool in advance and fill it with 20 to 25 cm of water 2 to 3 days before use.
Fertilized eggs should be hatched at a density of 1,000 per square meter. After about 10 days, check the eggs’ development and perform a second hatching if needed. Alternatively, hatch at a density of 10,000 per square meter. After 3 to 5 days, carefully collect the fry using a fine net.
IV. Fry Rearing
During hatching, introduce a small number of fry into the hatching pond with fertilized water. Two days after hatching, when the yolk sac is fully absorbed, the fry will start swimming horizontally and can feed on zooplankton such as rotifers and paramecia. Use 150 to 200 mesh nets to collect wild zooplankton, filter through a 100 mesh sieve, and feed the smaller individuals.
In colder seasons, wild zooplankton often consists of larger species unsuitable for newly hatched fry. A more practical approach is to feed them egg yolk for 5 to 7 days before introducing collected zooplankton or commercial fry feed.
Once the fry can consume artificial feed, their rearing method is similar to that of spring-grown goldfish. However, maintaining stable water temperatures above 15°C is crucial. Lower temperatures can weaken the fry, affecting their health and appearance.
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