The selection of broodstock is a critical first step in successful fish breeding. First, the broodstock must be purebred to ensure genetic consistency and quality. Next, they should be healthy, strong, and free from diseases or serious injuries. Third, the male-to-female ratio should be balanced, typically 1:1, to optimize mating success. Female broodstock should be at least 3–4 years old and weigh over 1.5 kg, while males should be 2–3 years old and weigh more than 1 kg. It's also recommended to prepare broodstock one year in advance rather than collecting them just before spawning. Keeping them in ponds for a full year allows their bodies to fully develop, leading to better spawning performance.
Next, the breeding of broodstock requires careful management. The development of their gonads and egg production depend heavily on the quality and variety of feed. A well-balanced diet that includes both plant-based and animal-based foods is essential to meet the nutritional needs of the broodstock. Avoiding monotonous feeding practices is crucial, as it can lead to nutrient deficiencies. Additionally, maintaining an optimal ecological environment is vital. Water quality must be closely monitored, with adequate oxygen levels maintained throughout the process. In autumn, pond water often becomes stagnant, so regular water changes and plankton management are necessary to keep the environment suitable for the broodstock. This helps in maximizing fat accumulation, which is important for high-quality egg production.
Proper care of broodstock in the previous year is also essential. During winter, the eggs develop, and by spring, only minimal feeding is needed to help the fish recover. If broodstock were not properly cared for the year before, their gonads may remain underdeveloped, and their body condition may be poor, leading to low fertility during artificial breeding.
Spawning conditions are equally important. The pond used for spawning should be between 0.2 to 1 mu in size, with a depth of about 1 meter. The bottom should be clean, with good water circulation and access to sunlight. Before use, the pond must be thoroughly disinfected, and incoming water should be filtered to prevent contamination. Fish nests made from materials like palm leaves, aquatic plants, or synthetic fibers should be placed in the pond. These nests should be evenly distributed and positioned 1 meter away from the shore. Common arrangements include suspended or flat columns, with flat columns being the most effective. Nests should be disinfected before use and replaced after each spawning session—typically within an hour—to maintain hygiene and encourage repeated spawning.
Aphrodisiac methods can also be used to stimulate spawning. Administering oxytocin injections, such as type I or II, can enhance spawning behavior. The dosage for females is generally 0.5 ml per kg of body weight, while males require about one-third to one-fourth of that amount.
Incubation is another key phase. Two types of hatcheries are commonly used: earthen ponds (0.5–1 mu, 1 m deep) and concrete ponds (20–50 m², 50–80 cm deep). The hatching density is usually 3,000–5,000 eggs per cubic meter. Drenching hatching involves placing the fish nests in a controlled indoor environment, where water is sprayed to keep the nests moist. The temperature should be maintained between 20–25°C, and the nests must be regularly watered without drying out. For running water hatching, fertilized eggs are washed using methods like mud, talcum powder, or water to remove the sticky coating.
Finally, once the fry emerge and the yolk sac is absorbed, they should be fed immediately. Water quality must be consistently maintained by replacing water gradually, ensuring the temperature difference does not exceed 3°C. Water should not be added while feeding to avoid disturbing the fry. During hot weather, diseases like gas bubble disease can occur, so regular water changes and removal of predators such as frogs, dragonflies, and aquatic insects are necessary to ensure the survival of the young fish.
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