This article is one of the exceptions to the rules of snakeheads.org. We usually publish original articles. This article is a summary of a book's chapter. The title of the book is Aquaculture in Taiwan by Chen Lo-chai, Fishing News Books, 1990. We were unable to contact the author for a request for publishing. Maybe he comes across this site and mails us his approval :-))))))
Four species of snakeheads occur naturally in Taiwan: Channa asiatica, Channa gachua, Channa argus and Channa maculata. The last is the largest species and is the one used in aquaculture. Since the early seventies snakeheads have been used in polyculture ponds for trash fish removal or for the control of juvenile tilapia resulting from excessive reproduction. There have also been attempts to monoculture snakehead. This fish is a favourite on the dining tables of the Cantonese. In some of the Cantonese communities in North America where snakehead is not available, the superficially similar bowfin (Amia calva) is sometimes marketed.
In Taiwan the snakehead becomes sexually mature in the second year of life and reproduces naturally from April to September when the water temperature is between 20 ° and 30 °. In January or February, brooders (600g minimum) are stocked into 60 to 1500 m 2, 30 to 100cm deep conditioning and spawning ponds which are earthen, rich in aquatic vegetation and low in plankton growth. Every brooder pair has 1 to 3 m2 of the tank, at a sex ratio 1 male for 2 female or 1 male for 3 female. During conditioning the snakeheads are fed with live tilapia of 30 to 40g each. Prior to spawning, a male fish clears the vegetation from a 1 m2 area as a nest site. During spawning the female takes an upside down posture near the surface at the nest site and releases a load of eggs. The male takes the same posture to ejaculate. Fertilized eggs are positively buoyant and are about 2 mm. in diameter. A 35 cm female can produce about 10000 eggs per spawning. A fish can spawn once a month, up to five times in a single season. After spawning parental fish stay in the nest site to guard eggs and fry. During the spawning season hatchery operators inspect spawning ponds every morning and gather eggs with fine mesh nets. .
In a ripe condition, males are more firm and slim, darker, have better defined dark marks on the body, particularly the dorsal fin, and have a smaller genital opening than females.
Ovulation and spermiation is induced through hypophysation. Every kg of females receives two intramuscular injections of a mixture of 10 rabbit units of HCG ( Synahorin, Puberogen, or Gonagen-forte) and pituitary homogenate from 1 to 1.5 kg of common carp (minimum size 500 g each) in 1 ml physiological saline. The interval between injections is about 12 hours. Male brood fish receive a single injection of the same dosage at the time females receive the second injection. In May and June during the peak of the spawning season, about 80% of the treated fish spawn naturally in about 30 hours after the first injection, with more than 90% fertilization. Artificial fertilization is not necessary. To ease management, every pair of injected fish is normally isolated into a 3 m2 compartment in the spawning pond partitioned by nettings, into a 3 m2 concrete trough, or into a 500 litre to 1000 litre plastic container where natural spawning will take place.
Fertilized eggs are transferred indoors into 60 cm diameter plastic tubs with 15 cm of water, 5000 to 8000 eggs per tub. Dead eggs turn opaque in about 10 hours and are removed manually. Sterilization through a 30 minute bath in 0.1 ppm malachite green solution or 0.5 ppm methylene blue solution may be necessary to control the spread of mould from dead eggs. At 20 to 22 °, hatching takes place in 45 to 48 hours; at 26 to 27° 36 hours, and at 30° 32 hours. Newly hatched yolksac larvae are about 4 mm long and float on the water surface. In three to five days, they reach 9 mm, exhaust the yolk supply and begin feeding. At this time they are fed with rotifers, daphnia, and copepods of less than 200 microns in size collected with 60meshper cm plankton nets from ponds.
After a month, the fish of different sizes are segregated into different ponds or into different compartments partitioned by nettings within the same pond. The stocking density is reduced as fish get larger. In five months the fish reach 400g and in 10 months, 600g. With a survival of 70%, the unit yield is about 12 metric ton/ha.
The snakeheads are fed with live fish such as tilapia and mosquito fish. A 10 cm long snakehead can swallow a 6 cm tilapia and a 600 g snakehead can swallow a 40g tilapia. The supply of live feeder fish is always a problem and many farmers instead use mixture of 80% trash fish paste and 20% wheat flour, soybean meal and eel feed. Such mixture is placed in a wire cage suspended in the water and is applied twice daily at a ration level of 57%. The feed conversion factor is between 8 and 12. When such artificial feed is used, a strict training programme must be maintained beginning from the nursery stage. Once a snakehead has acquired the taste of live feeder fish, dead artificial feed mix is no longer acceptable.
This summary was originally as chapter 4: Snakehead Culture published in: Aquaculture in Taiwan by Chen Lo-Chai; Blackwell Scientific Publication; pp. 39-42; ISBN 0852381654. The text was reduced to the facts snakeheads.org considered important for breeding snakeheads. In case, the author comes across this summary, snakeheads.org would be happy, if the author mails us and give us the permission to publish the original text.
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