How to Raise White Snakehead (Opniocepnalus argus var Kimnra)? Detailed Explanation of Breeding Technology Key Points

The white snakehead (Opniocepnalus argus var Kimnra), also called white mullet, commonly known as white snakehead bar, belongs to the order Perciformes, family Channidae, genus Channa. Its flesh is fine and tender, with few bones, and tastes delicious. White snakehead medicinal cuisine can promote lactation, generate muscle and invigorate blood, and is a nourishing treasure for postpartum women, the elderly and children. It is rich in nutrition and can be made into many famous dishes, such as stir-fried fish slices, white chrysanthemum fish shreds, white snakehead bar stewed with snake, etc.
Muscle composition of white snakehead: moisture 77.90, crude ash 1.10, crude protein 20.69, crude fat 0.76. Compared with some other precious freshwater fish: the crude protein content is higher than that of large-mouth catfish (14.85), and the crude fat is lower than that of large-mouth catfish (3.22), indicating that white snakehead is a medium-to-high-grade precious economic fish with low fat and high protein.
The amino acid content of white snakehead muscle nutrition is as follows: aspartic acid 2.08, threonine 0.95, serine 0.86, glutamic acid 3.92, glycine 1.09, alanine 1.32, cystine 0.13, valine 1.00, methionine 0.43, isoleucine 0.92, leucine 1.81, tyrosine 1.66, phenylalanine 0.88, lysine 1.80, histidine 0.52, arginine 1.10, proline 0.54.
The white snakehead has a white body color and a graceful posture, tolerates low oxygen, and has a certain ornamental value.
China has a long history of breeding snakehead bar, but no systematic research on breeding technology for the white snakehead bar had been carried out, leading to a reduction in natural resources. We began researching the white snakehead and its breeding technology in 1992, which received great attention from the fisheries sector and achieved good results. This project won the first prize for scientific and technological progress from the Provincial Water and Hydropower Department in 1997.
1 Biology of the White Snakehead
1.1 Morphological characteristics. The white snakehead has a white body color, a rod-shaped body, a flat head, larger scales on the head, fine scales on the tail, 47 dorsal fin rays, 38 anal fin rays, 63 lateral line scales, 13 gill rakers, 55 vertebrae, and a body length 7.8 to 8.2 times the body height.
1.2 Growth. The suitable survival temperature for white snakehead is 0 to 39°C. The optimal growth water temperature is 25 to 28°C, and at 12°C it basically does not feed. It has suprabranchial auxiliary respiratory organs, and the suitable pH value is 6.0 to 9.0. It likes to gather in groups, is good at jumping, and easily burrows into mud. It gains weight fastest in summer, with a daily weight gain rate of 3%.
1.3 Habits. The mouth is terminal, teeth are distributed on both sides of the upper jaw and the front part of the lower jaw, and it is mainly carnivorous. At the fry stage they will cannibalize each other, and they can be trained to eat compound feed. White snakehead cultured in ponds can reach sexual maturity in two years. In its gonadal development cycle, most eggs are at stage IV in February to March, enter stage III in March to April, are at stage V in May to July, which is the spawning period, and gradually return to stage III in August. The broodstock with a body length of 30 to 35 cm has a fecundity of about 15,000 eggs, with 8 eggs per gram. The relationship between body length and body weight is logW=3.032 logL-1.9433, and the relationship between individual fecundity Y (thousand eggs) and body length is Y=2.68532-79.08513.
　　
2 Artificial Propagation Technology
2.1 Broodstock cultivation. Choose pond conditions with a good water source. The pond size is preferably 60 to 100 sq m, with a pond height of 1.5 m and a water level of 1 m. Anti-escape facilities should be provided, and aquatic plants or water hyacinth should be present in the pond to provide shade and regulate temperature.
The white snakehead has suprabranchial respiratory organs and strong adaptability to the environment, so the stocking density can be higher than that of ordinary fish. Each square meter can hold 1 to 2 broodstock of 2 to 2.5 kg, with a male-to-female ratio of 1:1.
The white snakehead is a carnivorous fish. The broodstock feed generally uses small miscellaneous fish in the pond and some low-quality fry for feeding. It can also be fed terrestrial earthworms, aquatic earthworms, loach, etc. The feeding rate is generally 3 to 5% of body weight.
Before and during the spawning period, frequently flush and replace the pond water to ensure the pond water is fresh, so that the broodstock can develop normally.
2.2 Induced spawning and hatching. During the reproductive season, the female fish's abdomen is enlarged and elastic, and the genital pore is slightly red and protruding, while the male fish's genital pore is sunken. Generally, broodstock with a relatively white body color, robust physique and good maturity are selected.
The induced spawning agents include carp and crucian carp pituitary gland (PG) and chorionic gonadotropin (HCG), at 1 g PG and 1800 to 2000 international units HCG per kg of body weight. Injection can be given once or twice; the dose for male fish is halved, and the male-to-female ratio is 1:1 or 2:1. The effect time is related to water temperature: at 22 to 23°C it is 26 to 36 hours; at 24 to 25°C the effect time is 25 to 30 hours; at 26 to 30°C it is 18 to 22 hours. Generally, spawning should be controlled as much as possible before dawn. Snakehead spawning requires a quiet environment; if frightened during spawning, it will stop spawning. Place the fertilized eggs in an incubation box. The incubation facility controls the water exchange volume, with a circulating water volume of 50 cubic meters per hour, water temperature controlled at 22 to 27°C, dissolved oxygen controlled above 4 mg/L, and pH 7.0 to 8.0. Indoor incubation avoids the adverse factors of outdoor incubation, such as light, because the eggs float on the water surface and strong radiation causes embryo death; and enemies, as other wild miscellaneous fish eat the eggs. As long as favorable incubation conditions are ensured, the hatching rate can reach 90%. Static water incubation can also be used.
　　
3 Fry and Fingerling Rearing Technology.
Newly hatched larvae are black in body color, float on the water surface or lie on their sides near aquatic plants or suspended matter, gather at the pond edge and corners, and are quiet and not easy to move. The yolk sac accounts for about half of the body length. When the yolk sac gradually disappears and the fry can swim horizontally, transfer them to outdoor fry ponds for rearing.
3.1 Fry rearing. The stocking rate is generally 200 to 400 fry per square meter. At this time the pond water should be fresh and living, with sufficient suitable daphnia; otherwise the fry will cannibalize each other due to lack of food. At this stage, the suprabranchial respiratory organs of the fry are not yet fully developed, and their respiration depends entirely on dissolved oxygen in the water, so water quality must be maintained well. The key to high fry survival rate and fast growth lies in sufficient dissolved oxygen in the water and abundant suitable bait. During the fry rearing stage, enemies such as frogs and water centipedes must be removed. After 12 to 25 days of rearing, the fry can reach 5 to 8 cm in length, and the body color gradually changes from black to white starting from the top of the head. At this stage, the auxiliary respiratory organs of the fry are fully developed, their activity is very strong, and their food intake continuously increases. As the fry grow and develop, individuals enlarge, and pond density increases, they should be screened and transferred by grade to fingerling ponds for rearing.
3.2 Fingerling rearing. The rearing pond is 25 to 60 sq m, with a water depth of 0.5 to 0.8 m. Stock 5 cm long fry at 50 to 80 per square meter, and feed aquatic earthworms, terrestrial earthworms, sand earthworms, and the newly hatched fry of low-quality fish such as grass carp. White snakehead should be fed small meals more frequently, because this fish has the bad habit of greedy and gluttonous feeding; if fed too much at one time, it may die from overeating. The pond water should be changed frequently. Generally, one third of the water is drained from the bottom once a week, and then new water is injected from the inlet, so as to provide a comfortable living environment for normal growth and development. After 25 to 30 days of rearing, the fingerling size can reach 8 to 13 cm.
We adopt the following technical keys to improve the survival rate of fry and fingerlings: 1) improve water quality and keep the pond water fresh and living; 2) use reasonable stocking density and select suitable bait; 3) regularly screen the fry to keep the size relatively uniform.
　　
4 Adult Fish Culture. The white snakehead has strong adaptability and can be cultured either alone or as a supplementary species.
4.1 Supplementary culture: The white snakehead can chase and eat small wild miscellaneous fish in the pond, reduce feed waste in the pond, reduce dissolved oxygen consumption in the pond, and increase fish yield. Because its mouth diameter is smaller than that of large-mouth catfish, it does not pose a threat to the commercial fish being cultured, so farmers in various places can accept choosing this fish as a good supplementary culture species.
4.2 Pond conditions
(1) Culture conditions: Both earthen ponds and stone-built ponds can be used for culture, with a water depth of 1.5 to 2.0 m and a pond depth of 2.0 to 2.5 m. An appropriate production and sales management area is 1 to 1.5 mu. The pond should have convenient water inlet and drainage, and anti-escape facilities should be installed at the inlet and outlet and around the pond. Before stocking, pond clearing and preparation must be done well. Generally, quicklime is used, spreading 100 to 150 kg of quicklime slurry per mu, ensuring no dead corners are left unsprayed. After disinfection, add water after 1 week, and stocking can be carried out about 10 days after adding water.
(2) Culture technology: The stocking size should be above 10 cm (3 to 5 cun). During stocking, the size should be kept as uniform as possible. Before entering the pond, soak in 3 to 5% salt water for 10 to 12 minutes.
The stocking density is 2 to 3 fish per square meter, that is, about 1500 to 2000 fish per mu.
Types of feed to be fed: First, fresh animal bait, such as small miscellaneous fish, small crucian carp, wheat-ear fish, Hemiculter leucisculus, and fish beside fish skin. White snakehead loves to eat fish beside fish skin fish. Some river mussels can be appropriately placed in the pond to let them naturally reproduce fish beside fish skin fish to meet its needs. Second, fresh fish meat paste mixed with powdered compound feed, stirred with eel feed for feeding.
The feeding method adopts the four fixeds: fixed time, fixed quantity, fixed quality, and fixed location. The feeding amount is 6 to 10% of the fish body weight, gradually decreasing to about 6% as the fish body weight increases. During feeding, a lively scene can be seen of groups scrambling for food, and some even jumping out of the water.
Throughout the entire rearing stage, persist in patrolling the pond: first, see whether the anti-escape measures are appropriate; second, observe whether the fish activity is normal; third, observe changes in water quality. Especially in high-temperature seasons, water quality changes frequently and is prone to turning black and smelly. At this time, pond water should be exchanged frequently: a small exchange every three days, replacing one third of the pond water; and a large exchange every 10 to 15 days, replacing two thirds of the pond water, to keep water quality fresh. In winter and high-temperature seasons, the water level should be relatively raised to keep the water temperature relatively stable.
Under certain culture conditions for white snakehead, stocking fingerlings of 16 to 20 cm, after 5 months of growth, the survival rate is above 80%, and the yield per mu can reach above 500 kg.
The main growth period of white snakehead is from July to October, especially September is the best. From July to September, the average water temperature is in the range of 21.4 to 30.8°C. At this stage, seize the opportunity and strengthen cultivation to bring out the best growth effect.
　　
5 Feed.
The white snakehead is a fierce carnivorous fish and must undergo the domestication step of dietary conversion to achieve the goal of using compound feed to culture adult fish. At present in China, it is relatively difficult to use ultra-fine feed for food conversion, that is, the opening feed has not yet been solved. We began using powdered and small pellet feed for food conversion when the fry and fingerling size reached about 13 cm, and completed conversion to compound feed within 18 to 20 days. From 1994 to 1996, formula screening tests were carried out respectively. In a trial pond with an area of 25 sq m and a stocking density of 30 fish per square meter, after 22 days of rearing, 70% of the fingerlings could feed well on compound feed. Inspection began one hour after feeding, and the fullness of the test fish was grade 3 to 4. Because under natural conditions white snakehead has a habit of favoring wild miscellaneous fish, based on this, only by working hard on the color, smell and taste of the attractant and improving the feed formula could 91.8% of the test fish feed on compound feed after 15 to 20 days.
The basic feed for adult fish culture is composed of fish meal, soybean cake, wheat and corn, with minerals and special additives. The feed coefficient is 2.5 to 2.8. Nutritional components: crude protein 42.3 to 44.3; crude fat 5.65 to 6.51; crude fiber 1.23 to 2.83; ash 11.3 to 12.4; moisture 8.01 to 9.91.
　　
6 Disease prevention and control of white snakehead. Implement the principles of giving priority to prevention, combining prevention and control, emphasizing prevention over treatment, and treating early.
Enhance the disease resistance of the fish body, select fingerlings with a robust physique and uniform size, use reasonable dense culture, divide and rear in a timely manner, strengthen management, and achieve the four fixeds. Adjust the nutritional composition of the feed. Be cautious in fishing, transportation and handling to prevent injury to the fish body, and feed medicated bait for prevention.
Eliminate pathogens, thoroughly clear the pond, disinfect fingerling ponds in advance, disinfect before fingerlings enter the pond, disinfect the water body regularly, and when feeding live bait such as earthworms and miscellaneous fish, disinfect them with salt water before feeding.
Improve the environment, change water regularly, plant green plants, and increase oxygen.
Common diseases of white snakehead:
6.1 Ichthyophthiriasis. The pathogen is Ichthyophthirius multifiliis. After parasitism, the fry move slowly, and the harm is great. Use 2 ppm methylene blue for whole-pond splashing and soaking for prevention. For treatment, use 0.1 to 0.2 ppm mercurous nitrate for soaking, or whole-pond splashing; use malachite green at 0.2 ppm for whole-pond splashing for three consecutive days, with good results.
6.2 Trichodiniasis. Pathogens: several species of Trichodina can cause disease. They parasitize on the fish body surface and gill filaments, destroy muscle function and tissues, and affect respiration, leading to death.
Prevention and control methods: Use quicklime to clear the pond, keep water quality fresh, and splash the whole pond with 0.7 ppm copper sulfate and ferrous sulfate (5:2).
6.3 Saprolegniasis. The pathogen is a kind of Saprolegnia fungus. When the disease occurs, the muscles at the places where cotton-like masses grow on the body surface become stiff, the fish move slowly, float near the pond edge on the water surface without sinking, and gradually die.
Prevention and control methods: Try to avoid injuring the fish body during handling, especially in low-temperature seasons. Use formalin 20 to 30 ppm or potassium permanganate 30 to 50 ppm for whole-pond splashing, and 3 to 5% salt water can also be used for soaking for 5 to 10 minutes.
6.4 Hemorrhagic septicemia. It is common at the adult fish stage. The diseased fish has reddened fin bases and lower jaw, protruding eyeballs, loose scales, and swollen muscles. There is still no obviously effective treatment for this disease. Only prevention can be prioritized: thoroughly clear the pond, splash the whole pond with formalin 30 to 50 ppm, then inject new water, and avoid sewage sources as much as possible.