A Complete Analysis of the Key Technical Points for Snakehead Fry Rearing

Snakehead is the common name for the northern snakehead (Channa argus), also known as snakehead mullet, snakehead fish, wealth fish, snake fish, fire-head fish, and so on. It is fierce by nature, highly prolific, and has an enormous appetite, often able to eat all the other fish in a given lake or pond. In China it is a common food fish, large in size, fast-growing, and of economic value. Let us now take a look at the techniques for rearing snakehead fry!

The Breeding Habits of Snakehead

1. Spawning time: The spawning season of snakehead varies with climatic conditions in different regions. In South China it runs from mid-April to mid-September, peaking in May and June; in central China it runs from May to July, concentrated mostly in June. The breeding water temperature is 18°C-30°C, with the optimum being 20°C—25°C.

2. Sexual maturity: The age at sexual maturity of snakehead also differs slightly between regions. In South China, fish that have overwintered once and generally measure over 20 cm in body length already have mature gonads, whereas in the Yangtze River basin area they need to have overwintered twice and reach a body length of about 30 cm before they can spawn. They can reproduce naturally in waters such as ponds, ditches and reservoirs, and spawning grounds are generally found in shallow-water areas with lush aquatic plants.

3. Number of eggs released: The fecundity and number of eggs spawned by snakehead are related to the size of the parent fish. Fecundity is usually about 20,000-30,000 eggs per kilogram of body weight. A 0.5 kg snakehead (Channa maculata) generally spawns 8,000-10,000 eggs, with individual cases reaching 11,000-12,000 eggs.

Artificial Breeding of Snakehead

1. Breeding equipment: The breeding facilities for snakehead use the equipment employed for breeding the four major Chinese carps. The spawning pond is round, 8 m in diameter and 1.5 m deep. The fry hatching equipment consists of splash-type hatching jars, each holding about 500 kg of water, with a 60-mesh filter screen on the jar. The spawning nests are made of palm fibre sheets and mussel shells.

2. Selection and rearing of broodstock: For broodstock, natural catches from nearby ditches and lakes should be chosen as far as possible, with a size of over 80 g per fish, normal body shape, and no disease or injury. They are reared in ponds. When the water temperature is above 15°C, feed small fish and shrimp, snail and clam meat, soybean cake, etc. in small amounts, patrol the pond frequently to observe, and appropriately add fresh water.

3. Identification of male and female: The female is noticeably smaller than the male. The female has a circular urinary pore and an almond-shaped genital pore; when mature, the abdomen is swollen and soft, and the genital pore is slightly red and everted. The male has only one urogenital pore. The male-to-female ratio for pairing is 1:1.2.

4. Method of induced spawning: For natural spawning in ponds, no spawning-inducing drugs are injected. In early April, when the water temperature reaches 18°C and the sleeper goby (Odontobutis obscura) is seen swimming around in the upper layer of water at the pond edge, palm fibre sheets are laid and several large mussel shells are hung at the pond edge, and water is added so that the pond water forms a slight current to stimulate the broodstock into oestrus, allowing them to spawn naturally among the palm fibre sheets and mussel shells. For broodstock induced to spawn in the spawning pond, luteinizing hormone-releasing hormone analogue 2 (LRH—A) and human chorionic gonadotropin (HCG) are injected, in 2 injections, at the base of the pectoral fin. Each year on 6 April, when the water temperature is 19°C, the first injection of LRH—A is given; after an interval of 12 hours, a second injection of a mixture of LRH—A and HCG is given. After injection the fish are placed in the spawning pond, stimulated into oestrus with a slight flow of water, and palm fibre sheets and large mussel shells are laid out to let them spawn naturally.

5. Artificial incubation: The fertilised eggs are pale yellow and round, with a transparent egg membrane and strong adhesiveness. After the broodstock in the pond and spawning pond have finished spawning, promptly take out the palm fibre sheets and mussel shells bearing the fertilised eggs, gently wash off the mud and dirt, move them to the hatching jars, and hang the palm fibre sheets and mussel shells in the water.

Management of Snakehead Fry Rearing

1. Stocking of fry: Static-water cement ponds are used for rearing 1-year-old fingerlings, stocking 200-300 summer fry per sq m; slightly flowing-water cement ponds are stocked with 300-500 per sq m, reaching 0.05-0.10 kg per fish by the end of the year. Before stocking, the fish should be bathed in 2%-3% salt water for 3-5 minutes to kill pathogens and pests.

2. Feeding: The feed is mainly mosquito larvae, minced fish, and small fish and shrimp. The daily feeding amount is 5%-80% of the total body weight of the fish, fed 2-3 times a day. When feeding, use tapping sounds as a signal so that the fry form a conditioned reflex and rise to the surface in groups to compete for food.

3. Water quality regulation: When rearing in above-ground static-water cement ponds, the pond should be drained of waste once every 1-2 days, with a simultaneous water change of 1/3. When rearing in above-ground slightly flowing-water cement ponds, although there is no need for special water changes, the bottom should be drained of waste once every 7-10 days. When using semi-buried or fully buried cement ponds where waste removal is difficult, the siphon method can be used, cleaning out the waste once every 5-7 days. At the same time, add fresh water.

4. Netting and grading: Whenever the fry grow by one size grade, that is, every 3.5 cm of growth, they should promptly be netted, sieved and graded for rearing, so as to keep the fry stocked in each pond as uniform in size as possible.

5. Pond patrols and disease prevention: Persist in patrolling the pond twice a day, morning and evening. During patrols, pay attention to observing the fry's feeding and activity and changes in water quality, and solve any problems promptly. To prevent fish diseases, also regularly splash quicklime or bleaching powder solution.