Methods of Artificial Induced Spawning and Key Aquaculture Techniques for Snakehead

Artificial induced spawning uses injections of human chorionic gonadotropin and the pituitary glands of carp, bighead carp and bream.

In the Pearl River Delta region, pituitary glands of carp, bighead carp and bream are basically used as spawning agents. The dosage per 0.5 kg of body weight is: for female fish, 7 pituitary glands of bighead carp or bream (1 carp pituitary is equivalent to 2.7-3 bighead carp or bream pituitaries), given in two injections: the first injection of 2, and 5 more after an interval of 12 hours. At a water temperature of 23-25°C, spawning occurs about 18 hours after the second injection. For male fish, 1-2 pituitary glands of bighead carp or bream are used, and generally no second injection is given. At the time of injection, dissolve the hormone directly in physiological saline or distilled water. When using pituitary glands, place the glands in a mortar and grind them into powder, then add physiological saline or distilled water, mix evenly before use, and inject 1 ml per fish. A No. 6 needle is preferable for injection, and the needle insertion depth is about 1 cm. During injection, hold the needle at a 45-degree angle toward the front of the fish body and insert it at the scaleless area at the base of the pectoral fin. The hand must be steady and the movement quick. After injection, withdraw the needle and press the injection site with a finger to prevent the solution from flowing out along the needle. Snakehead (Channa argus) has no strict requirements for the spawning pond conditions. After injection, the brood fish can be placed in a cement pond or earthen pond with an area of 1 sq m and a water depth of 0.6-1 m, or even placed in larger water vats, wooden basins and other containers to spawn. Each spawning pond (or container) can hold one pair of brood fish (1 female and 1 male). The spawning pond or container should be covered with a net on top to prevent the brood fish from jumping out, and some aquatic plants should be placed on the water surface to shade the sunlight, or the container should be placed in a dark place, and the environment should be kept quiet. In this way, at a suitable water temperature, the brood fish can spawn and fertilize on their own, without the need for artificial insemination. Brood fish that have spawned the first batch of eggs can mature again after being reared for about 1 month, and can be induced to spawn again. After the eggs are laid, they initially sink to the bottom, and after absorbing water they float on the surface. They can be scooped out with a ladle or dish and placed in a small cement pond or a large plastic basin about 1 m in diameter for incubation. The day before spawning, disinfect the incubation pond with potassium permanganate solution. Generally, 10,000-20,000 eggs are placed per square meter of water surface. A shade shed is built over the incubation pond to avoid direct sunlight. During incubation, a certain water level and a constant water temperature should be maintained, preferably with a difference of no more than 2°C. Dead eggs (white, opaque) should be picked out at any time and egg membranes removed to prevent deterioration of water quality, and water should be changed in a timely and appropriate amount to keep the water fresh. Generally, fry can hatch in 2-3 days. Newly hatched fry resemble small tadpoles, with a grayish-black body, and rely on their own yolk sac for nutrition. After 4-5 days, the yolk sac is completely absorbed, and live water fleas need to be fed in a timely manner. The amount of water fleas to put in depends on how much the fry eat, and it is better to feed small amounts many times. After 5-6 days of feeding, the fry's body color turns yellow and the total length is about 1 cm, and they can be moved to a small pond for rearing.