The colony biology carp, also known as the Chinese silver carp, is capable of breeding in our country. In the northern regions, its spawning season typically occurs from September to November, while in the southern areas, it extends from November to January. These fish reach sexual maturity at 3 to 4 years of age. Female individuals can produce approximately 100,000 eggs per kilogram of body weight. Spawning occurs in batches, with mature eggs containing a single oil globule, making them buoyant. The egg size ranges from 1.22 mm to 4.5 mm, with some reaching up to 1.50 mm. Fertilized eggs are incubated at water temperatures between 16°C and 19°C, and hatch after 3 to 4 days of incubation. Newly hatched larvae measure about 4.42 mm to 4.6 mm in total length. Four days after hatching, their yolk sac is nearly depleted, and their mouth opens to approximately 0.75 mm to 0.80 mm, marking the start of feeding.
Broodstock for breeding comes from two main sources: wild mature individuals captured from the sea or selected from breeding groups. The best method for capturing broodstock is using fixed nets, which minimizes injury and improves survival rates. Broodstock are transported in water tanks within vehicles and held in pools with oxygen supply. For injured individuals, surface disinfection with potassium permanganate or malachite green is recommended, and if necessary, gentamicin injections can be administered to aid recovery.
Oxygen production, fertilization, and broodstock rearing are adapted to the environment, and artificial oxytocin is often used. Common oxytocin agents include gonadotropin-releasing hormone analogues (LRH-A) and human chorionic gonadotropin (HCG). These can be used alone or in combination, depending on the maturity level of the broodstock. Since maturation varies among wild individuals, mature broodstock are typically injected with ovulation-inducing agents 24 to 36 hours before spawning. When mature eggs are ready, either dry or wet fertilization is performed in a box, with seawater stirred for 5 minutes to ensure even mixing and high fertilization success.
For incubation, fertilized eggs are placed in conical cages with specific dimensions: a box diameter of 80 cm, a height of 60 cm, and a cone height of 40 cm. Egg densities range from 1.1 million to 500,000 eggs per cubic meter. Bottom air stones are used for aeration, ensuring gentle and uniform water movement. The best hatching water is filtered through sedimentation. Water changes are done 2 to 3 times daily, with full water replacement each time. Walls are washed every 2 hours to prevent embryos from sticking and to remove dead eggs promptly. Incubation duration depends on water temperature, with hatching occurring after 3 to 5 days. Maintaining clean water and sufficient dissolved oxygen can result in an 80% hatching rate.
Larval rearing and young fish cultivation can take place in controlled indoor environments or in outdoor earth ponds. Indoor breeding uses static water with micro-aeration and regular water changes, gradually transitioning to continuous flow. Larval stocking density is maintained at 0.5 to 1.0 thousand per cubic meter. Feeding typically starts with rotifers, artemia, copepods, and other suitable live feeds. Outdoor pond cultivation can also utilize ecological fertilizers to support natural food chains.
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