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Breeding techniques of carp seedlings
Whether carp pond aquaculture can achieve good economic returns largely depends on the seedling cultivation stage. This phase is critical, as it lays the foundation for healthy growth and high yields later on.
1. **Seed Acquisition**
Fertilized eggs are purchased from Heilongjiang and hatched on-site. The fertilized eggs have a diameter of approximately 2 mm and are kept in water with a temperature maintained between 19.5°C and 20.6°C. After 80 to 120 hours, the larvae hatch, with an overall hatching rate of about 80%. During the hatching process, there is a time lag between the emergence of each batch of larvae. Therefore, as soon as the first fry appears, they are collected separately to ensure optimal survival rates.
2. **Seedling Cultivation**
**Stage 1:**
Newly hatched larvae are placed on a hatching ring plate with micro-flowing water. The stocking density is set at 6,000 per square meter. At this early stage, the fry do not yet feed, so their primary needs are oxygen and careful handling. After 4–5 days, when the yolk sac is absorbed by two-thirds, feeding can begin. Due to the sensitivity of the fry during this period, many may die. To address this, I prepared specialized powdered feeds (S1, S2, S3) with crude protein content above 45%, combined with Artemia and water puffer (without worms), which significantly improved survival rates. Within half a month, the feeding rate reached 45%. At this point, the fry grow to about 3 cm and can be transitioned to feed S3.
**Stage 2:**
Once the fry reach over 3 cm, they are moved to a cultivation pond. The pond is designed with three layers: 3 meters, 1 meter, and 0.5 meters deep. The top layer is filled with water, while the drainage hole is controlled via an overflow pipe. The pond must be covered to protect the fry from direct sunlight, heavy rain, and other environmental hazards.
Feeding is done according to 25%–45% of the fish’s body weight, with small portions given 8 times daily. Before each feeding, the system is cleaned, air supply is stopped, and water flow is halted to ensure proper digestion and reduce stress.
**Stage 3:**
When the fry grow beyond 10 cm, they are transferred to a larger pool measuring 6 meters by 4 meters. Before moving them, the cement pool is disinfected using a 20 ppm potassium permanganate solution, then thoroughly cleaned. When transferring the fry, each fish is dipped in a 10 ppm Dimethicin solution for 3–4 minutes to prevent disease. Once the fish reach 25 cm or more, weighing 50–100 grams, they are considered ready for breeding. At this stage, the breeding phase is deemed successful, and the fish are safe for further cultivation.