Rapid breeding of Freshwater White Pomfret

From May to November 2009, five leisure fishing grounds in Yuetang District of Xiangtan adopted an efficient culture model of adult freshwater Pomfret at 80:20 in ponds, that is, 80% of freshwater white Pomfret (feeding fish) and 20% of fish (filter feeding fish) were cultured in ponds. Full-price expanded pellet feed is the main feed. The stocking time of freshwater Pomfret is from May 6 to 10, when the water temperature is stable above 20 ℃. The release time of silver carp and bighead carp was in the first and middle of April. Disinfect the fish before releasing the fish. The release of fish species is that freshwater Pomfret accounts for 80.5% of the total release, and silver carp and bighead carp account for 10.5%, 19.5%. The specification of fish species is 8-15g/ tail of freshwater white Pomfret, and silver carp and bighead carp are self-bred large species. The feed is a special expanded pellet compound feed for freshwater Pomfret, with protein content > 32%, crude fat > 4.5% and crude fiber < 6%. In 2009, 5 fishing farms developed water surface 3.0hm2 for Pomfret culture. At harvest, the average yield per mu was 752kg, and the freshwater white Pomfret accounted for 81.3% of the total yield, 88.6% of the total yield, and the survival rate was 98%. After about 80 days of feeding, the white Pomfret can reach the listing specification (tail weight more than 500g) by the end of July, which is one month earlier than the ordinary breeding method. At this time, the rotation can be carried out or listed through fishing, the market price is high, in order to improve economic benefits. The average net profit of the five fishing grounds is 8000 yuan per mu, and the input-output ratio is 1 ∶ 2.56.The benefit is very good. The main technologies are summarized as follows.

Main measures of Freshwater White Pomfret Culture Technology

1. Pond condition

The suitable area of the adult fish pond is 0.2-0.6hm2, the water depth is about 1.2m, the water quality is fresh, the transparency is 25-40cm, the bottom is flat, the bottom silt is about 10cm, and the drainage and irrigation is convenient. It is best to be equipped with an aerator 0.2-0.3kw per mu, and the pond should be cleaned and disinfected before releasing the fish seed.

two。 Seedling stocking

The breed of freshwater Pomfret requires neat specifications, strong physique, disease-free and injury-free. Fish species into the pond, the operation should be careful to avoid fish injury, and with 3-4% salt for disinfection. After long-distance transportation of fish, the fish should be kept in a cage for a period of time before going into the pond, and the fish should be disinfected after a little recovery. The stocking density of fish species is generally 1000-1100 fish per mu with 8-15g/ tails, and can be mixed with other fish species with 50 silver carp and bighead carp, with a tail weight of 100-150g.

3. Bait and feeding

The main results are as follows: 1) the main culture of freshwater Pomfret in the pond should be fed with full-price expanded pellet feed, and the feeding technology is related to fish yield, commercial fish specification, fish culture cost and economic benefit. The freshwater Pomfret is a fish that is constantly foraging, with short intestines and fast digestion and absorption. Therefore, it is necessary to feed more times. The feeding frequency is 4 times a day, 2 times in the morning and 2 times in the afternoon, 40% in the morning and 60% in the afternoon. The reference formula of compound feed is: fish meal 5%, soybean cake 20%, vegetable cake 30%, rice bran 15%, wheat bran 8%, flour 15%, corn 10%, mineral prepowder 2%. In general, the daily feeding rate of freshwater Pomfret combined with pellet feed is 3% and 6%. Fresh water Pomfret needs domestication and feeding. The fish is easy to domesticate, floating and grazing in clusters. It is domesticated three times a day, each time 30min, and it can be domesticated to the food table within 5 days.

2) the amount of basal fertilizer applied in the pond is the same as that in the four main domestic fish ponds. Before the fry is put into the pond, fermented manure 200kg is applied as the base fertilizer per mu, and a small amount of topdressing is applied 3-4 times according to the water quality during the breeding period, each time 50kg.

3) using black light to lure insects to feed fish. The working principle of black light lamp is the same as that of ordinary fluorescent lamp, which is composed of ballast, starter and lamp tube, but the lamp tube does not emit incandescent light, but a kind of light which can attract flying insects. Just put the black light on the 50cm high above the surface of the water and turn it on at night. Flying insects, especially moths, within a radius of 5m around the light will fly to the light and fall into the fish pond under the lamp, which happens to be eaten by the freshwater white Pomfret. The electricity charge is 0.1 yuan per 10 hours (that is, one night), but the flying insects can reach several kg, or even dozens of kg, which greatly reduces the feed cost of freshwater Pomfret.

4) to open up a wide range of feed sources and add some animal scraps to feed the fish. Freshwater Pomfret is an omnivorous fish with a wide range of food habits. Farmers can feed freshwater Pomfret with the scraps of poultry and livestock in slaughterhouses. On the one hand, freshwater Pomfret likes it very much, on the other hand, the growth rate of freshwater Pomfret is faster when fed with poultry and livestock. The launching price of poultry and livestock is low and easy to obtain, which can greatly reduce the feed cost. Freshwater white Pomfret is also very fond of snail, clam and earthworm meat. Farmers can use their spare time to obtain these easily available natural feed to feed freshwater white Pomfret, and they can also raise some screws, clams and earthworms for freshwater white Pomfret. In terms of plant feed, green fodder such as goose grass and Sudan grass can be planted in free space. Using idle water surface to raise duckweed to feed freshwater Pomfret, the effect is also good.

4. Daily management

1) keep patrolling the ponds regularly and observe the changes of water quality, adding fresh water every 3-5 days in summer and 7-10 days in autumn. You can turn on the aerator at noon on a sunny day for 2 hours to increase the amount of dissolved oxygen in the water; in cloudy, rainy or muggy weather, once you find a fish floating head, turn on the aerator or add new water in time. Although the freshwater Pomfret is resistant to hypoxia, it will float its head or even flood the pond when the dissolved oxygen in the water is below a certain limit. As long as a floating head occurs in freshwater Pomfret, there will be no food intake for 3-4 days or very little food intake, and it will take 5-6 days to return to normal. These 5-6 days not only do not grow, but also consume, that is to say, each floating head equals no growth for 10 days. Therefore, the management of water quality in the process of culture is very important. New water should be replenished in time, transparency should be kept around 25cm, and mechanical oxygen enrichment measures should be taken if necessary.

2) Disease prevention should be done well. May-September is the season for the onset of freshwater white Pomfret, so we should regularly disinfect the pond water with quicklime or bleaching powder to prevent the occurrence of fish diseases. In addition, floating aquatic plants such as duckweed can be raised near the fish pond, which can be used as fish feed and as a shade place for fish in high temperature season. It can also increase the amount of dissolved oxygen in the water, prevent water quality from being over-fertilized and regulate water quality.

5. Disease treatment technology

Freshwater Pomfret has strong disease resistance, and the survival rate is generally more than 90% when the water temperature is above 26 ℃. When the water temperature is 15-20 ℃, young fish are easy to suffer from melon disease, white skin disease, ring disease and so on. During the overwintering period, freshwater Pomfret is also prone to skin rot, water mildew, rotifer and so on.

1) small melon disease: the pathogen is the larva or adult of many-bearing small melon insects. A large amount of mucus appeared on the body surface of the diseased fish, and when it was seriously infected, it appeared as a white cloud in the water. At the same time, there is congestion at the base of dorsal fin and caudal fin. The first control method is to raise the water temperature as much as possible, and the other is to use crushed red pepper 2.5kg to boil and sprinkle all over the pond.

2) White skin disease: the pathogen is Pseudomonas aeruginosa. The body surface, dorsal fin, caudal fin and forehead of the diseased fish are slightly whitish at first, and the scales fall off as soon as they are touched. In severe cases, the fish lose balance, spin in the water, swim slowly, or hang on the surface of the water head up or tail down. The time from onset to death is short, and the mortality rate can reach more than 60% within 3 days. The first control method is to sprinkle the bleach solution of 1mg/L concentration in the whole pool, once a day for 3 days. The other is to soak the diseased fish 30min with oxytetracycline solution of 25mg/L concentration.

3) skin rot: the pathogen is bacteria. The skin of the diseased fish is inflamed, and in severe cases, the scales fall off, the muscles rot, are round, swim slowly, lose balance, and die soon. The control method is to sprinkle the bleach solution with 1mg/L concentration all over the pool.

4) Water mildew: the pathogen is water mold. The diseased fish had clustered hyphae on the body surface, moved slowly, tissue necrosis, and soon lost balance and died. The method of prevention and treatment is to sprinkle methylene blue with 0.1mg/L concentration in the whole pool once a day for 3 consecutive days.

5) finger ring disease: the pathogen is ring worm. Sick fish are extremely disturbed by Gill stimulation, or swim crazily on the surface of the water, or swim sharply at the bottom of the water, lose appetite, lose weight and gradually die. The control method is to soak the diseased fish in potassium permanganate solution with 20mg/L concentration for 20-30min. Or sprinkle all over the pool with the mixture of 0.5mg/L concentration copper sulfate solution and 0.2mg/L ferrous sulfate solution.

6) rotifer: the pathogen is rotifer. The fish gets sick only after it is parasitized by a large number of rotifers. The control method was sprinkled all over the pool with the mixture of copper sulfate and ferrous sulfate (5 ∶ 2) of 0.7 mg/L.