The first one is tilapia.
Tilapia is a small and medium-sized fish. At present, it is the focus of freshwater aquaculture in the world, and it is considered as one of the main sources of animal protein in the future. Tropical fish native to Africa, belonging to Cicadellidae, similar to perch. Usually live in fresh water, can also live in salt water with different salt content, and can live in shallow water of lakes, rivers and ponds. Strong adaptability and strong adaptability to water with less dissolved oxygen. Most tilapia are omnivorous and often eat plants and debris in the water. This fish can also breed in small waters. It can even grow in rice fields.
Brief introduction of tilapia
Tilapia, commonly known as African crucian carp, belongs to Perciformes, Perciformes, Cicadellidae and Tilapia (also known as Sparidae, Sparidae). The genus is native to Africa, with more than 600 species, and currently cultivated 15 species. Tilapia is a small and medium-sized fish. Its shape and individual size are similar to those of crucian carp, and its fins are as varied as mandarin fish. Broad-salt fish can live in both seawater and fresh water; Resistant to hypoxia, generally inhabiting the lower layer of water, but inhabiting the water layer with the change of water temperature or fish size.
Tilapia has a wide range of eating habits, mostly plant omnivores, very greedy and eat a lot; It grows rapidly, especially in its infancy. The growth of tilapia is closely related to temperature. The growth temperature is 16 ~ 38℃, and the optimum temperature is 22 ~ 35℃.
Tilapia was first introduced from Singapore to Taiwan Province Province in China in 1965 by Wu and Guo Qikun. In memory of these two people, it was first called "Wu Guoyu". 1957 was introduced to China from Vietnam, also known as "Vietnamese fish". Because it is native to Africa and looks like a local crucian carp, some people call it "African crucian carp".
There are two kinds of tilapia introduced from Yingshan Hot Spring in Hubei Province: one is called Mozambican tilapia, and 1972 was received from jingshan county; The other is Nile tilapia, 1979 was introduced from Hubei Fisheries Research Institute. After they settled down, they all lived well.
Dr. Modadugu Vijay Gupta of India developed and disseminated the cheap technology of freshwater aquaculture (using tilapia) and won the 2005 World Food Prize.
Characteristics of tilapia
Tilapia is omnivorous, resistant to hypoxia, intolerant to high and low temperatures, and strong in reproduction.
1. Omnivorous: Tilapia is a plant-based omnivorous fish. In tilapia ponds, the contents of digestive tract are mostly organic debris and other plant feeds (such as aquatic plants and commercial feeds), followed by phytoplankton, zooplankton and a small amount of benthos.
2. Hypoxia tolerance: Tilapia has strong hypoxia tolerance. When the suffocation point is 0.07-0.23 mg/L and the dissolved oxygen in water is 1.6mg/L, tilapia can still survive and reproduce. When the dissolved oxygen in water is higher than 3 mg/L, the growth is not affected.
3. Not tolerant to low temperature and high temperature: The survival temperature range of tilapia is 15-35℃. When the water temperature is lower than 15℃, tilapia is dormant. The highest critical temperature of tilapia is about 40℃-4 1℃, the optimum growth temperature is 28℃-32℃, and the breeding temperature of tilapia is above 20℃.
4. Strong reproductive ability: Tilapia has early sexual maturity, short spawning cycle, low requirements for reproductive conditions when young fish hatch in oral cavity, and naturally reproduce in large waters. Tilapia reached sexual maturity in 6 months, and about 200 grams of female fish had about 1, 000- 1, 500 eggs. The male fish in the breeding period has beautiful wedding smoke color, and there are two orifices in the abdomen: anus and urogenital orifice, and white semen flows out from the squeezed abdomen. There are three holes in the abdomen of female fish, namely anus, genital hole and urogenital hole. When the water temperature is 18℃-32℃, the mature male fish has the ability of "digging the nest", and the mature female fish enters the nest to mate, lays mature eggs and puts them in the mouth immediately, so that the eggs are fertilized and fertilized eggs develop in the female fish's mouth. When the water temperature is 25℃-30℃, the young fish can hatch in 4-5 days. The young fish leave the mother when the yolk sac disappears and has certain ability.
Nutritional value of tilapia
The meat of tilapia is delicious and tender, and it is delicious whether braised or boiled. According to the determination, Nile tilapia contains protein 20.5g, fat 6.93g, 1 48kcal, calcium 70mg, sodium 50mg, phosphorus 37mg, iron1mg, vitamin B 1 mg and vitamin B2 0. 1 mg. Tilapia has become the main cultured fish in the world.
Freshwater culture of adult tilapia
I. Pond culture
1. Pond conditions
The farm should be located in a sheltered, sunny, abundant water, fresh water, pollution-free, quiet and convenient place. The pond area is 3 mu to 5 mu, the water depth is 1.5 m to 2 m, and the thickness of the pond sediment is 20 cm to 30 cm. Each pond is equipped with 1 impeller aerator with power of 1.5 kW.
2. Clean the pond and fertilize it
Clean and disinfect the pond before releasing fish. Generally, in the first ten days of April, the pond is cleaned with 75 kg ~ 100 kg of quicklime per mu. After 7 days, water is added to the depth of 1 m, and then 300 kg ~ 400 kg of decomposed manure is applied per mu, and a small amount of green duckweed or red duckweed can be added.
3. Fish stocking
Every spring, when the water temperature rises and stabilizes above 15℃, winter seedlings are stocked. Generally, pond owners raise 1500 ~ 3000 fish per mu, and 40 ~ 70 silver carp and bighead carp are mixed to control water quality. When mixed with other fish, 200 ~ 500 fish can be raised per mu.
Step 4 feed the bait
Tilapia can be fed 2-3 days after entering the aquaculture water surface. Tilapia has a wide range of food habits. In the case of artificial feeding, it can be fed with various feeds, such as wheat, corn and cake, which are all high-quality feeds. The content of protein in feed should be 32% ~ 35% at first, and the daily feeding amount should be 3% ~ 5% of the total weight of fish. When the individual size is about 200g, the feeding amount can be adjusted to 2% of the total weight of the fish, and the protein content in the feed can be ensured to be 27% ~ 29%. When the individual reaches about 300g, the tilapia enters the fastest growth period, the daily feeding amount is kept at 65438+ 0% ~ 2% of the fish weight, and the protein content in the feed is above 35%. Feed twice a day at 8:00-9:00 am and 3:00-4:00 pm respectively.
5. Daily management should pay attention to patrol the pond day and night.
(1) Measure the water temperature and air temperature every morning, noon and evening, measure the pH value 1 time every week, and measure the transparency twice. Patrol the pond in the morning and evening 1 time.
(2) After the fingerlings enter the pond, the pond water should be kept dark brown with a transparency of 25cm ~ 30cm. Generally, the fertilizer is applied once a week 1 time, and the livestock manure per mu 150 kg ~ 200 kg each time. When the weather is clear and the water transparency is more than 30 cm, the amount of fertilization can be appropriately increased; When the water quality is too fat, we should reduce or stop fertilization and inject new water. In hot season, water is generally changed 1 ~ 2 times a week, and 20% ~ 30% of the pool water is changed each time.
(3) Adhere to healthy farming, standardize operations and prevent fish diseases. Soak the fish 10 minutes to 15 minutes with 5% salt solution or 0. 1 mg potassium permanganate solution per liter before the fry enter the pond. Every 65,438+00 days to 65,438+05 days, 65,438+05 kg ~ 20 kg of quicklime water is sprayed on each mu of the whole pond, the pH value of the pond water is adjusted to be slightly alkaline, and biological agents are used to improve the microbial structure of the pond and improve the water quality. When the dissolved oxygen is low and the fish has a slight floating head, turn on the aerator.
Second, paddy field culture.
Land of fish and rice, can double harvest. Attention should be paid to scientific feeding in interplanting tilapia in rice fields.
1. Stocking preparation
After the completion of the paddy field project, two weeks before stocking, 75 kg ~ 100 kg of quicklime water per mu was sprayed in the fish ditch and ridge for disinfection, and the bottom of the ditch and ridge was raked 1 time the next day, so that lime slurry and sludge were fully mixed. Before seedling release 1 week, fertilizer water from fermented animal manure was applied, with the dosage of 200 kg per mu, for cultivating natural bait in water.
2. Lead time
Generally, about 5 days after transplanting rice seedlings, the seedlings will be released when they turn green. In some places, in order to increase the growth period of fish, it is also an effective and good way to put fish in the fish ditch in mid-May and put them in the ground after the seedlings turn green.
3. Stocking method
Fish species should be selected with strong physique, strong activity, no damage and neat specifications. The stocking density should be reasonable. Generally, 200 ~ 300 tilapia fingerlings with specifications of 5 cm ~ 6 cm can be released per mu, with grass carp, carp and other fingerlings 150 ~ 200. The specific stocking amount can be flexibly mastered according to paddy field conditions, water quality environment, irrigation and drainage conditions and management level.
4. Inventory operation
Fish should be disinfected before entering the pond. Generally, fish should be soaked in 3% ~ 5% salt water for 5 minutes ~ 10 minute. Fish should be released in sunny morning or evening, but not in rainy day or sunny noon.
5. Feeding and fertilization
Generally speaking, rice farming in Luo Fei is not fed, and it grows entirely by ingesting natural bait. However, the natural bait in rice field is limited, so it is suitable to feed some bait to accelerate its growth and improve its yield. Feed bait twice a day, and the feeding amount can be controlled within 2 hours after eating bait. There is no special requirement for applying base fertilizer and farmyard manure to fish-farming rice fields. Such as urea, ammonium sulfate, etc. They are all used as topdressing, and should be applied in small amounts several times, one and a half fields at a time. It is forbidden to apply fertilizer directly in the fish ditch.
Thirdly, cage culture.
Tilapia can be raised singly, mainly or together in cages. The species of fish should be of large size, and the size of the fish in the box is generally 10g ~ 50g. When the dissolved oxygen is above 3 mg per liter, the stocking density is 3 kg ~ 20 kg per cubic meter.
Fourth, flowing water culture.
Tilapia is one of the main objects of high-density or "factory" culture in running water at present. The aquaculture pond should not be too large, generally it is advisable to raise fish from 30 square meters to 50 square meters, and keep the dissolved oxygen in the pond above 3 mg per liter. Intensive farming needs to be fed with compound feed with comprehensive nutrition, and the protein content of the feed should be about 30%. Feed it 5 ~ 6 times a day, and the feeding amount is 2.5% ~ 3% of the fish weight.
Several key problems in tilapia culture
Among many tilapia seedlings, it is generally believed that the seedlings bred by interspecific hybridization of tilapia have the characteristics of fast growth, large size, good cold tolerance and high male rate, which is widely recognized by farmers. Its commodity names mainly include: Oni, Oza, Wu Guoyu, Androgyny, etc. At present, the quality of fry produced by different fry production units is quite different. Farmers should select a seedling with the fastest growth rate and the highest male plant rate from many varieties through breeding.
The parthenocarpy tilapia produced in China objectively did not reach the male rate of 100%. In the breeding production, there are more or less inferior offspring, which increases the breeding density, consumes a lot of feed, and even fails to meet the commodity specifications (its value is only about 20% of the normal product, so it is called cat fish), which seriously affects the output and benefit of tilapia breeding production. In order to solve this problem, there are the following measures:
1, and standard coarse matching and grading culture is implemented. Breeding producers should be equipped with enough standard thick ponds for secondary fry. The standard thickness of primary fry is about 20-50g, and that of secondary fry is about 200-400g. Then, the male fish will be sorted and put into the ponds to develop commercial fish. This can not only solve the problem of "cat fish" over-breeding, but also avoid the waste of water surface in the early stage of breeding.
2, artificial regularly eliminate inferior offspring. According to the characteristics of tilapia seedlings swimming in groups, in the breeding season, inferior seedlings are collected and removed from the pond every 2-3 days.
3, moderately stocking carnivorous fish. After the tilapia fry are stocked, some ferocious carnivorous fish such as Silurus meridionalis, barracuda and spotted snakehead (the stocking specifications are based on the tilapia that cannot be stocked) are appropriately stocked to prey on the offspring of tilapia culture. At present, farmers in Gaozhou generally mix 20 catfish per mu. If the pond is cleaned every crop, 20 spotted snakeheads, if the pond is not cleaned.
4. Batch culture and pool cleaning after harvest. Except the small reservoir in the mountain pond, it is really impossible to clean the pond with dry water. In general, the traditional way of catching and releasing is changed, and batch farming is carried out, and the pond is cleaned after harvest.
Due to the lack of funds and other reasons, many farmers first consider the price rather than the quality of feed when choosing feed. Choosing cheap and inferior feed will not only reduce feed cost, but also reduce production efficiency. Generally speaking, tilapia compound feed is required to ensure its crude protein content according to each growth stage, and the key is that it does not contain toxic and harmful substances. Otherwise, the normal growth of fish will be affected, and a large number of fish will die, resulting in reduced production. From the long-term practice of farmers in Gaozhou city, we know that the main influencing factors of feed on tilapia culture are: first, feed mildew, and second, compound feed contains more rapeseed cakes with toxins. Most of the dead fish in tilapia culture ponds in Gaozhou city are the above reasons. In particular, it is most common to produce a large number of dead fish by feeding feed containing about 20% rapeseed cake. Through the anatomical follow-up observation of these tilapia, with the increase of feeding time, the liver and gallbladder of the fish become larger and lighter in color. By the time of death, the liver turns pink, the gallbladder turns pale yellow and transparent, and the liver and gallbladder increase by 2-3 times. After the fish ponds with dead fish were switched to rapeseed cake-free feed and detoxification medicine feed, the phenomenon of dead fish gradually disappeared. We believe that rapeseed cake is highly toxic, and it has not been detoxified in production or the detoxification effect is not good, which leads to the toxicity accumulation of tilapia after eating. When the detoxification ability of liver and gallbladder reaches the limit, it will lead to the death of fish. Therefore, in tilapia production, we should pay attention to not using moldy feed and not using or using less compound feed containing rapeseed cake.
In order to make tilapia culture high-yield and efficient, in addition to stocking high-quality fish and feeding high-quality feed, it is necessary to let the fish have a good growth environment in order to make the fish grow normally and quickly. The key is to ensure the supply of dissolved oxygen in water. Excessive stocking density will lead to insufficient supply of dissolved oxygen in water and affect the normal feeding, digestion and absorption of fish. Therefore, the producer should set the stocking density according to the water capacity (pond depth), water supply, and whether or not an aerator is equipped. The stocking amount is generally controlled at about 1-2 fish per cubic meter of water. Farmers should grasp the best stock in production practice. When the fish reaches the production specification period, the feeding amount of about 2% of the body weight can be eaten under normal weather conditions.
Summary of experience in disease prevention and control of tilapia
In recent years, with the increase of export volume and the continuous improvement of people's quality of life, the quality and safety of aquatic products have been paid more and more attention, and the demand for pollution-free aquatic products has been increasing. Therefore, it is imperative to carry out standardized and healthy farming of tilapia, and one of the keys to standardized and healthy farming is disease prevention. The author summarized the experience of tilapia culture in Huazhou in recent years for reference.
The prevention of fish diseases is mainly based on prevention, and measures are mainly taken, such as strictly controlling stocking density, adjusting aquaculture water quality, feeding fresh feed with comprehensive nutrition, and regularly sampling and dissecting fish. Once fish diseases are found, aquatic professionals should be asked to diagnose them in time and prescribe the right medicine under the guidance of professionals. General measures are:
1, thoroughly clean and disinfect the pond; 2, fry, fish into Tang Qian strict disinfection; 3. After the fry and fingerlings enter the pond, spray 90% trichlorfon crystals of 1g/m3 once in the whole pond. Spray with 1-2g/m3 bleaching powder (28% available chlorine) once after half a month; 4. Keep the water quality fat, lively, tender, refreshing and slightly alkaline; 5. The dead fish should be fished out in time, disinfected and buried in the soil; 6. The equipment used in the sick fish pond shall be dipped and disinfected, and the water in the sick fish pond shall not be discharged at will without disinfection.
The use of fishery drugs must be strictly in accordance with the relevant provisions of the State Council and the Ministry of Agriculture. The usage and dosage of external drugs and oral drugs shall conform to the provisions of the aquatic industry standard "Guidelines for the Use of Fishery Drugs for Pollution-free Food (NY507 1-2002)".
The second kind is freshwater pomfret.
brief introduction
Short-tailed pomfret: Also known as freshwater pomfret. Piaractus mitrei: Also known as freshwater pomfret. Piaractus brachypomus (Cuvier, 18 18) is a tropical and subtropical fish native to the Amazon River in South America. Freshwater pomfret (hereinafter referred to as freshwater pomfret) has the characteristics of miscellaneous eating habits, fast growth, large size, less diseases, easy fishing, less meat, delicious taste and rich nutrition. It is a valuable fish to expand the pond culture object and increase the output per unit area, and can also be used as an ornamental fish in the juvenile stage. Freshwater pomfret was introduced to Taiwan Province Province, China in 1982, and it was popularized in freshwater fish ponds after successful artificial propagation. 1985 was introduced from Taiwan Province province to Guangdong province for trial planting, and 1987 was successfully propagated artificially. Later, it was gradually popularized throughout the country and became one of the famous and special varieties with the highest annual output.
morphological character
The fin has no hard spines. Dorsal fin18 ~19; Gluteal fin16 ~18; Abdominal fin 8. There are two swimming rooms, the back room is longer than the front room. Sideline scale 82 ~ 98. There are two rows of upper and lower teeth, with notches on the tooth surfaces and protruding tips. The number of gill rakes in the first branchial arch is 30 ~ 36. Have an obvious belly. The gastric sac is U-shaped and relatively enlarged, and its length is about 1/5 of that of the intestine. There is pyloric caecum (pyloric prolapse) at the junction of stomach and duodenum, and there are fat blocks around intestine and viscera.
According to 42 specimens with body length 1 18 ~ 144 mm, the average body length is 1.87 times the body height, 3.35 times the head length and 13.73 times the tail stalk length. The head length is 1.92 times the body thickness; 4. 18 times the length of the kiss; 4.27 times the diameter of the eye.
It's a bit like a sea pomfret, with a flat side and a thick back, and the mouth is in one position, which is unnecessary. The head is small, equal in length and height. Eyes of the same size are slightly higher than the corners of the eyes. The tail is bifurcated, and the lower leaf is slightly longer than the upper leaf. There are fat fins on the back, the starting point of the dorsal fin is slightly opposite to the ventral fin, the body surface is covered with small round scales, and there are slightly serrated ventral ridge scales from the base of the pectoral fin to the anus. The body color is silver gray, the chest, abdomen and buttocks are red, and the tail fin edge is black. Fish have black spots on their bodies. The stars of adult fish disappear, but the body color of adult fish will change somewhat due to the influence of environment. The short-covered giant fat carp raised in the indoor water cluster box in alkaline water lacking sunlight is dark in color, dark gray to black, while those raised in the pond are white body, silver scale, black tail and red fin with four colors, and the fish species are extremely beautiful and dotted. This kind of fish is a good ornamental fish because of its size and color characteristics.
Eating habits
Freshwater pomfret is an omnivorous fish with a developed digestive system. It has an enlarged stomach and pyloric sac like a carnivorous fish. It not only feeds on animal feeds such as small fish, shrimp and benthos, but also feeds on plant feeds such as aquatic plants, vegetables and algae. Under artificial feeding conditions, peanut bran, bean cake and compound feed can be fed. In the fry stage, it mainly feeds on unicellular algae such as diatom and dinoflagellate and zooplankton such as rotifer, cladocera and copepod. It was observed that the newly hatched larvae were nourished by yolk, and the intestine formed after 4 ~ 5 days. When it grows to 5.6 mm, it begins to eat plankton, mainly micromonospora and rotifers. When the total length is about 16 mm, the food in the digestive tract is mainly Daphnia; When the total length is 4 ~ 5 cm, the main food in the stomach is Daphnia and cladocera; When the total length is about 6 cm, the food composition of the digestive tract includes not only various plankton, but also plant debris and artificially fed feed. When the total length is more than 7 cm, its food composition is mainly various plant debris and feed. Therefore, plankton is the main food in the fry stage.
Growth characteristics
Freshwater pomfret is large and grows rapidly. The largest individual can reach 20 kg, and the weight in the first year can reach 1000 g or more. In Guangdong, the fry hatched in that year can grow to the market specification of more than 500 grams by the end of the year, and the maximum can reach more than 1000 grams; In the second year, it can grow to about 2000 grams. In Zhejiang Province, the artificially propagated freshwater pomfret seedlings were cultivated into summer flowers from late April to early May of that year. After more than four months, the tail weight was about 240 grams, which also reached the standard of edible fish. The population growth of freshwater pomfret is relatively uniform, and individual differences are small. In the case of adequate feed, species generally don't kill each other. But fish will bite each other when they are hungry, and some will die because their tail fins are eaten. Therefore, on the one hand, it is necessary to ensure sufficient feed in the feeding process, on the other hand, it is best to adopt the method of polyculture with other fish.
Adaptability to some ecological factors
Freshwater pomfret belongs to tropical fish, and the suitable temperature range is 12 ~ 35℃, and the optimum growth temperature is 24 ~ 32℃. If the water temperature is lower than 12℃ for two consecutive days, there is a danger of freezing to death. The fish has strong hypoxia tolerance, and can still survive when the dissolved oxygen is 0.5 mg/L. It is suitable for breeding in fat fish ponds or in salty fresh water with salinity of 10‰. Freshwater pomfret likes to live in the middle and lower layers of water, has a gentle temperament, has the habit of moving in groups, is easy to catch, has small and dense scales, is not easy to be injured, and is suitable for long-distance transportation.
Overwintering techniques of freshwater pomfret
Freshwater pomfret is a tropical and subtropical fish, and it will die when the water temperature is lower than 12℃. When the water temperature is 18℃ ~ 19℃, it can survive, but it is easy to get sick or even die in large numbers. Therefore, the overwintering management of freshwater pomfret is particularly important.
First, the selection method
According to the overwintering conditions and production needs, the overwintering of freshwater pomfret can be divided into two types. One is low-temperature seed preservation, that is, the water temperature in the overwintering pool is maintained at 18℃~ 23℃, but only seeds can be preserved and cannot grow. The other kind is temperate culture, that is, keeping the water temperature in the overwintering pond between 24℃ and 32℃ can keep the appetite of freshwater pomfret, and insist on proper feeding, which can not only survive, but also grow and develop, enhance physical fitness and improve disease resistance. The overwintering water temperature of parent fish is preferably between 26℃ and 32℃, which can not only ensure its vigorous feeding, but also promote its gonad development. In the specific operation, all localities should flexibly choose the wintering mode according to the thermal energy resources and the needs of wintering production. General wintering methods are:
1. Plastic shed overwintering
In other words, plastic greenhouses are used to keep warm for the winter. Set up an arched shed with steel pipes or bamboo above the wintering pool, seal it with nylon cloth, and open the shed doors on both sides to facilitate air circulation and artificial feeding.
2. Geothermal water for winter
Where there are geothermal resources, hot water can be used for winter. Choose a suitable place to drill a hot water well, and introduce geothermal water into the wintering pool with a thermal insulation pipe, which should be buried deep underground to avoid heat dissipation. The wintering pool covers an area of more than 5 mu and the water depth is more than 2 meters. It is necessary to detect the temperature and quality of geothermal water to make it suitable for the survival and growth of freshwater pomfret.
3. Factory waste heat for winter
Excess hot water can be used to overwinter freshwater pomfret in places where there is waste heat from factories, but attention should be paid to the analysis of excess hot water to make its water quality suitable for freshwater pomfret to survive. For example, the remaining hot water in a closed power plant can only be used for seed conservation, and its water quality is not conducive to embryo development, so that fertilized eggs of freshwater pomfret cannot hatch and emerge.
4. Other ways
For example, areas rich in resources such as industrialized fish farming and raw coal and crude oil can use boilers to boil water for the winter; In small-scale wintering areas, large-capacity solar water heaters can also be used to supply water for wintering.
Second, be prepared.
Freshwater pomfret should be cultivated in autumn before entering the wintering pond, so as to strengthen their physique and improve their disease resistance. In order to strengthen feed feeding, the daily feeding amount should be 5% ~ 8% of the fish weight, and the protein content in feed should be about 30% ~ 35%. The formula can be fish meal 10%, bean cake 25%, vegetable cake 20%, rice bran 10%, and mixed impurities 6544. Because pomfret often inhabit the middle and lower layers of water, the pellet feed should be made heavier, which is convenient for eating as soon as possible and reduces waste. Before stocking, the pond should be cleaned and disinfected, and the wintering pond should be thoroughly disinfected with quicklime or bleaching powder. When freshwater pomfret moves into the wintering pond, it is necessary to pay attention to the change of water temperature and catch it before the arrival of the first cold air. Fish caught when the water temperature is lower than 16℃ cannot be used as overwintering fish species. At the same time, fish of different specifications must overwinter in different pools, and the fish species should be healthy, smooth and trauma-free. The overwintering density should be appropriate, generally 40,000 to 50,000 fish per mu, and the parent fish should not exceed 200 kilograms per mu.
Third, feed correctly.
Results the water temperature in the overwintering pool can be maintained at 24 ~ 32℃ for a long time, and the freshwater pomfret can still eat normally. Generally, after the pomfret enters the overwintering pond for 3-4 days, it can be fed with artificially mixed heavy pellet feed, and the crude protein content in the feed should reach about 30%, and fresh leaves or duckweed should be fed appropriately to adjust its appetite. When feeding, we should adhere to the principle of "more times, less quantity and no bait".
Fourth, strengthen management.
The following work should be done:
1. Personnel management, patrolling the pond day and night.
It is necessary to measure the water temperature every day, observe the fish situation, and deal with problems in time.
2. Reasonable water transfer to ensure water temperature.
Do a good job in water quality adjustment, and change the water every month 1 time, and each change of water shall not exceed 1/3. When changing water, pay attention to control the water temperature to keep it at 24℃ ~ 32℃, and the temperature difference before and after changing water shall not exceed 2℃.
3. Put prevention first, and prevent diseases and harms.
Freshwater pomfret is easy to get sick because of its long overwintering period, high density, poor water quality, so it should be soaked in methylene blue for 10 to 15 minutes before entering the pool. When the water temperature is 18℃ ~ 20℃, the young fish are easy to suffer from gourd disease, white skin disease, third generation disease and so on. , especially gourd disease, is easy to cause explosive death. In addition, it will also be infected with trichuris, wheel disease, gill flagelliasis, bacterial gill rot and so on. If you find sick fish, you should prescribe the right medicine in time and be careful not to use trichlorfon.
4. Improve conditions and strengthen management.
Be sure to remove the dirt from the bottom of the pool. If there is no sewage drainage equipment at the bottom of the pool, you can use siphon to suck out feces, residual bait and other dirt, and change water regularly. Keep the wintering area quiet and try to avoid scaring the wintering fish. Birds and livestock are prohibited from entering the pool, enemies such as snakes and eels are eliminated, birds are prevented from attacking fish, and a good wintering environment for freshwater pomfret is ensured.