Culture of snakehead

Snakehead, commonly known as snakehead and talented fish, is a fierce fish at the bottom. It likes to live in water with dense aquatic plants and more silt, and has strong adaptability to water quality, water temperature, dissolved oxygen, pH value, etc., and dives into the silt for wintering in winter.

First, the biological characteristics of snakehead

The head of snakehead is pointed and flat, with a large mouth and a slightly flat cylindrical body. The whole body has irregular black patterns, the fins have black and white patterns, and the caudal fin is round. Snakehead is a ferocious carnivorous fish. Before its body length is 3 cm, it mainly feeds on copepods, cladocera and chironomid larvae. When the body length is 3 ~ 8 cm, it mainly feeds on aquatic insects, shrimp and small wild fish, and feeds on various fish in the adult stage.

The growth rate of snakehead is relatively fast. Generally, in lakes with good food conditions in the middle and lower reaches of the Yangtze River, the weight of 1 year-old fish can reach about 200 grams, that of the second-year-old fish can reach about 500 grams, and that of the third-year-old fish can reach more than 800 grams. It grows fastest at 2 ~ 3 years old. But in the waters with poor food conditions, the growth is also slow.

The sexual maturity age of snakehead is generally 2 years old and its weight is over 500 grams. The fecundity is about 1 10,000 ~ 20,000 eggs. The spawning period is from April to August, depending on the difference of water temperature conditions in different places. When the temperature is suitable (mid-June), spawning can generally reach its peak, and it is often empty at one time. For example, in areas with low water temperature, eggs can also be laid in batches. The spawning ground is generally located in the lush aquatic plants with more silt at the bottom of the water. Before spawning, the female and male parent fish * * * collect leaves, water plants and so on to build oval ovaries. Oviposition is mostly carried out in the early morning or evening when the weather is sunny and warm and the environment is quiet. After spawning and in vitro fertilization, golden eggs separated in beads can be seen floating on the fish nest. There are couples of male and female fish under the fish nest. This behavior of protecting the offspring of snakehead, from laying eggs until the young fish live independently (body length is about 10 mm). People often take advantage of this juvenile protection characteristic of snakehead to catch its parent fish in the grass where snakehead eggs are found. Snakehead eggs are floating eggs with large oil balls, which can float in running water or still water. After hatching, the larvae are black, suspended on the water surface by the buoyancy of oil balls, lying on their sides and inhabiting by secreting mucus clusters. The survival rate of eggs and newly hatched larvae is low, because they are suspended on the water surface and easily swallowed by other fish and frogs.

Second, artificial propagation of snakehead

The breeding period of snakehead in natural water is from April to August. In artificial breeding, the time of inducing labor varies according to the water temperature in different areas, and it is generally from mid-May to mid-June in the Yangtze River basin. The criteria for choosing spawning parent fish are: mature parent fish with age of two winters and body length of about 30 cm. At present, there are mainly pituitary gland and gonadotropin in Cyprinus carpio. There are 4 pituitary glands per kilogram of female parent fish (about 8 mg), and the hormone is 800 ~1200 international units per kilogram of body weight. One or two injections can be used, or two oxytocin agents can be mixed. The dose of male parent fish is halved. From the test results of production units around the world, the effect of fish pituitary gland is better than that of hormone, and the effect of inducing labor is better than that of 1 injection. However, there are also failures in inducing labor, mostly due to the poor gonad development of the female parent fish of snakehead. Therefore, selecting parent fish with good gonad development is the key to improve the artificial spawning rate of snakehead.

According to the experience of various places, after injecting oxytocin, putting 1 into the pool has a better oviposition effect on snakehead. If more than one pair of parent fish are put in the spawning pond, the male fish will be injured by fighting for the female fish. If the male fish is bitten, it will affect its sperm output and reduce the fertilization rate of eggs. When the paired parent fish is put into the spawning pond, it should be shaded immediately to avoid head injury when the parent fish jumps. Another point to note is that the number of injections is determined according to the spawning situation of female fish. Because the eggs of snakehead are produced in batches at one time, if there are still spawning or spawning parent fish after1~ 2 injections, another injection can be made, and spawning can be basically achieved after about 20 hours. But the later, the lower the fertilization rate. In general small-scale production, a small cement incubator can be used, with the specification of10× 5× 0.8m.. Set up a shed for shade on the incubator to avoid direct sunlight. Disinfect the pond water with 0.07 mg/L malachite green solution 24 hours before spawning (no obvious blue color can be seen in the pond after applying the medicine), and apply malachite green twice after spawning and before leaving the membrane to prevent water mold. When transferring fish eggs from the spawning pond to the hatching pond, it is not appropriate to fish them directly with nets, but to take them out with water in a fish tray to prevent them from breaking. When the water temperature is about 25℃, they can hatch in about 40 hours.

The cultivation of hatched snakehead fry is an important link in the process of artificial reproduction. After hatching, the remaining egg membranes should be taken out in time to prevent the rotten egg membranes from polluting the water quality. The feeding of fry begins when the yolk sac disappears on the sixth day after hatching, so it is better to feed artificially cultivated Daphnia.

Third, adult fish culture

1. Mixed culture of snakehead carp

The mixed culture of snakehead in carp pond is mainly aimed at removing wild miscellaneous fish in fish pond. 450 ~ 600 snakeheads with body length less than 10 cm can be stocked on each hectare of water surface. When stocking, carp should be longer than snakehead to avoid being preyed by snakehead. The mud pond does not need to be specially fed with snakehead feed.

2. Mixed culture in the "domestic fish" pool

In the fish pond where four big fish are mainly raised, 450 ~ 750 fish are mixed per hectare, and the body length is less than 50% of that of domestic fish.

3. Mixed culture with tilapia

When mixed with tilapia, a bamboo fence or nylon net curtain with a height of 1.5 meters should be set around the pond to prevent fish from escaping. Water hyacinth can be planted on the surface of fish ponds with a water depth of about 1.5 meters, which can play a dual role in shading and hiding snakehead. At first, 7,500 snakehead fish with a body length of less than10cm can be stocked per hectare, and after two or three times of dragnet classification, the large ones are retained and the small ones are removed, and the density is reduced to prevent eating and eating. The final breeding density is 1500 fish/hectare. If there are not many fish ponds, nylon net cloth can be used to divide the fish ponds into several small ponds to raise snakehead with different specifications. In order to make the snakehead eat enough tilapia, the tilapia can be kept in a part of the pond with a suitable mesh nylon net. The young fish bred by tilapia can be used as feed for snakehead fish after passing through the mesh. In this way, after about half a year's feeding, the snakehead fish can grow to about 500 grams of commercial fish when it is released 10 cm.

4. Single rearing

Monocultured snakehead is full of fresh fish, and the cost is very high. It must be domesticated to swallow artificial compound pellet feed. The domestication method is to mix 80% minced small mixed fish with 20% flour or other adhesives to make granular bait. At the beginning of domestication, this feed can be mixed with Daphnia and fed, and the number of live baits such as Daphnia will be gradually reduced, until finally, Daphnia is not used and all artificial compound feed is fed. High-density single-culture snakehead generally uses domestic fish or carp culture ponds, and bamboo fences or net fences are set around the ponds to prevent snakehead from jumping up easily when the density is high. The depth of the pool is about 1.5 meters, and aquatic plants such as water hyacinth and water hyacinth should be planted on the water surface to achieve the purpose of shade and concealment. From mid-May to mid-June, the snakehead fish will be stocked. The stocking density varies with the size of fish species. About 90,000 fish can be stocked per hectare for 3-5cm fish, 45,000 fish can be stocked per hectare for10-0/5cm fish, and 7,500 fish can be stocked per hectare for fish over 20cm. In addition to the artificial feed mentioned above, it is best to feed enough fresh small fish and shrimp, earthworms, fly maggots and so on in areas where there are sources of small miscellaneous fish. In places where natural feed sources are insufficient, in addition to the above feed used for taming snakehead, the following feed formula can also be used: 70% of wild fish sauce, 20% of soybean powder, 5% of yeast powder and appropriate amount of trace elements. The other feed formula is 50% animal feed (fish meal, leftovers of livestock and aquatic products, blood meal, etc.), 48% plant feed (bean cake, wheat bran, etc.) and 2% bone meal. No matter whether fresh feed or artificial compound feed is fed, "four settings" should be implemented, and it should be flexibly mastered according to the water temperature, weather and feeding situation of snakehead (whether there is residual feed or not).