Key Points of Snakehead Farming Technology and Detailed Explanation of Daily Management Methods
The snakehead has strong environmental adaptability and low requirements for pond water quality, and can be farmed at high density. Each mu of pond can stock 8000-10000 fingerlings, and the yield can reach 4000-5000 kg. The snakehead grows fast, and fry in early spring can be raised into market-size fish in the same year. Snakeheads have few diseases and a high survival rate, and adult fish are easy to transport, facilitating long-distance sales.
Artificial Breeding of Snakehead
1. Selection of brood fish: Mid-May each year is the breeding season of the snakehead. Mature and robust male and female snakeheads should be selected as brood fish at a ratio of 1:1. The method for distinguishing males from females is as follows: the female snakehead has a swollen and soft abdomen, black and white in color, with an obvious outline of the ovary, a groove appearing in the center, and a protruding, pink genital pore; the male snakehead has a purplish-red body color, with neatly arranged transparent white small round spots from bottom to top on the dorsal fin, a darkened abdomen, and a slightly enlarged, slightly concave, triangular, pale pink genital pore. Before induced spawning, place the male and female fish separately in cages to rest for a day without feeding, which is more conducive to spawning.
2. Induced spawning of brood fish: The female fish is injected twice, with the first injection being 1/3 of the total dose, 18-26 hours apart, and the remaining dose injected at once; the dose for the male fish is half that of the female fish, injected at the time of the female's second injection. Most fish are injected via the chest cavity, at 45° to the fish body, with a needle depth of about 1 cm. Commonly used hormones include carp and crucian carp pituitary, with a dose of 4-8 per kg for female fish and half that for males; or human chorionic gonadotropin, with 16000-24000 international units per kg for female fish and half that for males.
3. Egg incubation
① Artificial simulation of the natural environment for incubation: After injection of the spawning agent, place males and females at a 1:1 ratio into a pond to allow them to spawn, fertilize, and hatch naturally. After the fry hatch, use the snakehead's parental care behavior to let them tend the fry freely. This method saves labor and time, but its disadvantages are a low fry survival rate and inconsistent growth and development.
② Artificial cage incubation: After injection for induced spawning, place males and females at a 1:1 ratio into 4-6 sq m cages to spawn and fertilize, then remove the brood fish and put them into a large pond. Place the eggs into 40-mesh cages, with 10000 fertilized eggs per cage, and incubate using a micro-flow water method. The hatching rate depends on the fertilization rate and water quality. At 22-27°C, it takes 32-48 hours. Check frequently and remove unfertilized eggs in time.
4. Fry and fingerling rearing: Before they grow from hatching to 2 cm, they should be placed in cages made of 40-mesh net cloth with specifications of 1 m × 0.5 m × 0.5 m, at a density of 2000 fish per sq m. 4-5 days after hatching, feed rotifers or cladocerans, copepods, etc., using the method of small amounts and multiple feedings, once every 4 hours, for 3-4 days; afterward increase the feeding amount and reduce the frequency, gradually transitioning to twice a day. When the snakehead fry reach 2 cm, transfer them to cages made of 8-16 mesh summer-fry net cloth, with an area of 10-15 sq m, preferably rectangular, at a density of 500-600 fish per
5. Feeding bait: The bait is mainly zooplankton. At 4-5 cm, feed minced fish meat plus zooplankton. To prevent dirt and filamentous algae from clogging the mesh, brush and wash once a day, change cages once a week, and thoroughly disinfect the cages.
Snakehead Rearing Technology
1. Pond construction: Choose an east-west oriented, rectangular pond with a mud bottom, a pond depth of 2-2.5 m, and a water depth of 1.5-2 m. Anti-escape facilities must be installed at the inlet and outlet. Apply quicklime at 100-150 kg per mu 15 days before farming for thorough disinfection.
2. Fingerling stocking: Before the fingerlings are put into the pond, soak them in 3%-5% salt water for 10-15 minutes, then put them into the pond. For fingerlings with a body length of 10-14 cm, the stocking density is 9000-10000 fish per mu; for fingerlings of 16-20 cm, the stocking density is 8000 fish per mu.
3. Daily management: Pay attention to observing the snakehead's feeding, activity, disease trends, and environmental changes. In spring, change 4/5 of the pond water every week; in the high-temperature season, do a small water change every 3 days and a large water change every 7 days. Install anti-escape nets at the inlet and outlet, and it is best for the pond bank to be more than 50 cm above the water surface. The discharged sewage should undergo necessary sewage treatment.
4. Feed feeding: The feed for raising snakeheads includes artificial compound feed, freshwater or marine small trash fish, and offal from livestock and poultry slaughter. Before feeding small trash fish, they need to be sorted to remove fish with hard spines, such as yellow catfish. Before feeding, use tapping as a signal to gather distant fish near the feeding platform, reducing feed waste. The initial feeding amount is 10% of body weight, and later it can be appropriately reduced to about 5% of body weight. It should be fed spoonful by spoonful, which reduces feed waste. Feeding should follow the “four fixed” principle, and 3-4 feeding points should be selected for each pond. Using intensive farming methods, for fish with a body length of more than 10 cm, after 8-9 months of farming, the survival rate is 75%-80%, the average body weight is 0.5-0.7 kg, and the yield per mu is 4000-5000 kg. Plant some aquatic plants in the pond, such as cattail, tape grass, alligator weed, etc., with the planting area controlled at 1/3 of the pond area.
Prevention and Treatment of Common Diseases
At present, in the process of snakehead farming, common diseases include hemorrhagic disease, white skin disease, saprolegniasis, ichthyophthiriasis, and trichodiniasis. This article will provide a brief overview of the common diseases.
1. Hemorrhagic disease
[Pathogen] Various bacteria and viruses.
[Symptoms] There are bleeding stripes perpendicular to the lateral line on both sides of the body wall at the base of the pectoral fins and near the posterior edge of the gill cover; after bleeding symptoms appear, mass sudden death occurs in 3-4 days; outbreaks are likely from June to September.
[Prevention and treatment] After winter fishing, thoroughly clear the pond, and disinfect the bait fish with salt water before feeding; splash formalin over the whole pond to make the pond water concentration reach 20-30 ml per cubic m, or splash chlorine dioxide solution over the whole pond to make the pond water concentration reach 0.5 g per cubic m, and repeat once after 4-6 days. Oral administration of Yufukang No. 2 or Yuxuesan or Yuxuekangtai is acceptable, with the dosage used according to the instructions.
2. Red skin disease
[Pathogen] Pseudomonas fluorescens.
[Symptoms] Local bleeding on the body surface and loss of scales, especially on both sides of the abdomen, with fin erosion. The fish moves slowly, and diseased fish often float on the water surface, weak and powerless. It often secondarily develops saprolegniasis until death.
[Prevention and treatment] Thoroughly clear the pond with quicklime to avoid injuring the fish body; disinfect with 0.5 mg/L Xiaoling or other chlorine-containing disinfectants, such as trichloroisocyanuric acid, sodium dichloroisocyanurate, chlorine dioxide, etc.; orally administer Yufukang or Yuxuekang, using 250 g per 100 kg of fish weight or according to the instructions, mix into the feed and feed continuously for 3-5 days.
3. Saprolegniasis
[Pathogen] Saprolegnia.
[Symptoms] It occurs at all stages of snakehead growth. Early infection is not easy to observe, and it breaks out in large numbers when the water temperature rises to about 18°C; blood spots appear on the body surface, appetite decreases, the fish body becomes emaciated, melanin at the lesion site fades, appearing grayish white, dull and lusterless, and the fish swims alone away from the group. Finally, cotton-like white filamentous bodies grow out, and the muscles become turbid white until death.
[Prevention and treatment] Before stocking, use 100-150 kg per mu of quicklime for dry pond clearing, and regularly disinfect adult fish ponds with quicklime or bleaching powder; during the disease outbreak period, potassium permanganate at 30-50 g per cubic m can also be splashed over the whole pond. Be careful during fry and fingerling capture, transport, and handling to prevent injury to the fish body, and soak in 3%-5% salt solution for 10-20 minutes
4. Trichodiniasis
[Pathogen] Trichodina.
[Symptoms] It mainly harms the fry and fingerling stages of the snakehead. It can occur all year round, but is more prevalent from April to July, with a suitable temperature of 20-28°C. It is prone to occur in cases of small ponds, shallow water, poor water quality, insufficient bait, excessive stocking density, and continuous rain; diseased fish have excessive mucus, most or all of the body appears white, swim slowly, become emaciated, and die from difficulty breathing.
[Prevention and treatment] Splash a mixture of copper sulfate and ferrous sulfate (ratio 5:2) over the whole pond to make the pond water drug concentration reach 0.7 mg/L. This can effectively kill Trichodina on the body surface and gills of snakehead fry and fingerlings.