Can Litopenaeus vannamei be cultured in Zhidan County, Yan 'an City, Shaanxi Province?

Penaeus vannamei, also known as white-skinned shrimp, white shrimp and white shrimp, is native to the Pacific coast of South America. Ecuador has the most concentrated distribution along the coast and is one of the three highest shrimp species in the world today. Suitable for farming in tropical and subtropical coastal areas. Penaeus vannamei is similar to Penaeus vannamei in China (the largest individual can reach 23cm), and its normal body color is light blue gray. Compared with other cultured Penaeus vannamei in China, it has the following advantages: the breeding cycle is long, and fry can be produced all year round; Strong ability to resist the change of water environmental factors, which can be cultured in seawater and fresh water ponds: it can survive out of water for a long time, can be sold as live shrimp, and the product price is high; Fast growth, strong adaptability, strong disease resistance, can be used for high-density culture, the survival rate is generally above 70%, and the nutritional requirements for feed are low. When the content of protein in feed accounts for 25% ~ 30%, it can meet its normal growth needs; Shrimp shell is thin, small, and has a large meat content, which can reach more than 65%.

Biological properties

Taxonomically, Penaeus vannamei belongs to Arthropoda, Crustacea, Decapoda, Swimming Suborder, Penaeidae, Penaeidae and Penaeus. Its appearance is similar to that of Penaeus vannamei in China, with thin shell and bluish gray (or white) body. Its forehead is slightly bent downward, and the tip length is no more than 1 the second section of the antenna handle. The head and breastplate are short (so the meat yield is high), and the lateral groove of the frontal angle is short, and the stab disappears in the stomach. There are liver spines and obvious liver ridges on the head and breastplate; The first antenna has a Shuang Bian, which is roughly equal in length. 1 The upper limbs of the third pair of feet are well developed. The fourth and fifth steps have no upper limbs; The abdomen has a back of 1 to 6; There is a central groove in the tail section, but there is no lateral thorn; Female shrimp has no seminal vesicle, which belongs to the open type, and the sperm pod is easy to fall off, so it is difficult to obtain fertilized eggs. The inner limb of the first abdominal limb of the male shrimp is specialized as a connector, which is slightly drum-shaped, and the surface is covered with valleys and protrusions of different shapes and sizes.

I. Morphological characteristics

Penaeus vannamei is similar to Penaeus vannamei and Penaeus vannamei in China. Adult shrimp can reach 23 cm in length, with thin shell, normal blue-green body color, no stripes and feet like chalk, so it is called white-footed shrimp or white-footed shrimp. The length of the front horn tip of Penaeus vannamei is no more than 1 the second section of the antenna handle, and its tooth type is 2 ~ 9/2 ~ 4. The breastplate of the head is short, and the ratio to the abdomen is 1:3, so the meat yield is relatively high. The lateral sulcus of frontal angle is relatively short and disappears below the puncture on the stomach. There are liver spines and antenna spines in the head and breastplate, but there are no spikes and gill nails. The liver ridge is obvious. 1 The antenna has a Shuang Bian. The inner whip is thinner than the outer whip, and the length is roughly equal, but they are all relatively short, which is about 1/3 of the antenna rod length. 1 ~ 3 pairs of walking feet have very developed upper limbs, 4 ~ 5 pairs of walking feet have no upper limbs, and the fifth step has embryonic outer limbs. The fourth to sixth abdominal segments have backs, and the caudal segment has central sulcus, but there is no marginal spur.

Penaeus vannamei has no seminal vesicle. Mature individuals's seminal vesicle is located between the 4th and 5th pairs of feet, and the exoskeleton of the seminal vesicle is inverted "Q". It belongs to the open external genitalia. At present, there are five kinds of prawns with open genitalia, namely Penaeus vannamei, Penaeus vannamei, Penaeus orientalis, Penaeus vannamei and Penaeus schrenckii. The seminal vesicle of open connector is easy to fall off, and it is difficult to artificially propagate shrimp seedlings. The inner limb of male 1 abdominal limb is specialized as a connector, which is drum-shaped, and its surface is covered with grooves and protrusions of different shapes and sizes.

Whether the male and female of Penaeus vannamei are mature or not, its big tentacles are obviously bent near the base, which can not be used as a basis for judging sex.

Second, the life history

After the Penaeus vannamei grows into a mature shrimp in the natural sea area, it leaves the shallow water area and lives in the deep sea area far from the shore, with a general water depth of about 70 meters. The seawater temperature is 26 ~ 28℃ and the salinity is 34‰. Adult shrimp develop into a kind of shrimp here, and then mate and lay eggs. Eggs hatch into larvae, from nauplii, flea larvae, mysid shrimp larvae to larvae, which belong to zooplankton and also grow in such stable waters.

When the shrimp larvae develop to the late larval stage, they begin to swim to shallow waters such as estuaries and harbors and settle in coastal shallow waters. In the nearshore shallow water area, there are abundant nutritional bait, and the salinity, temperature and environmental factors change greatly, which is beneficial to the growth and development of larvae. In the near future, after several months of growth and development, it becomes an adult shrimp and returns to the deep water with stable environment again. The gonads begin to mature, mate, lay eggs and complete the cycle of life alternation.

The natural habitat of Penaeus vannamei is muddy seabed, with water depth 1 ~ 72m, water temperature of 25 ~ 32℃, salinity of 28 ‰ ~ 34 ‰ and pH value of (8 0.3). Most adult shrimps live in deep waters far from the shore, while young shrimps like to feed and grow in estuaries rich in bait organisms. Penaeus vannamei, like other shrimps, lies at the bottom of the pond during the day and moves at night. Penaeus vannamei molts in the middle of the night, that is, at 9:00- 12:00 pm. The interval of molting is about 20 days. Penaeus vannamei has a mild temperament, and cannibalism among individuals is rarely seen under experimental conditions.

Three. environmental requirement

Under the condition of artificial culture, the requirements of Penaeus vannamei for water environment are as follows:

1, water temperature requirement: Penaeus vannamei is a tropical shrimp, and the suitable culture temperature is 25 ~ 32℃. Under the condition of gradual warming, Penaeus vannamei can tolerate high temperature of 43.5℃. However, the adaptability to low temperature is general, and feeding stops below 65438 08℃, and death begins at 9℃.

2. Salinity requirements: Penaeus vannamei has strong adaptability to salinity, with the salinity adaptation range of 5 ‰ ~ 45 ‰ and the optimum salinity range of 10 ‰ ~ 25 ‰. Under the condition of gradual desalination, it can also grow normally in fresh water with salinity of 0 ‰ ~ 2 ‰;

3.pH value: In nature, the adaptive range of Penaeus vannamei to pH value is 7.3 ~ 8.6, and the optimum pH value is 8.0 0.3. When the pH value is lower than 7 or higher than 9.5, the activity of Penaeus vannamei decreases.

4. Dissolved oxygen: Litopenaeus vannamei has outstanding anti-anoxia ability, and its tolerable minimum dissolved oxygen value is1.2 mg/L/L. However, in the process of culture, it is required that the dissolved oxygen value of water should be greater than 4.0mg/L and not less than 2.0 mg/L.

5. Water color: oil green or reddish brown is the best water color;

Four. Molting and growth

The growth rate of shrimp is related to two factors: one is the frequency of molting, that is, the interval of molting; The second is the growth and proliferation rate, that is, the weight that can be increased from molting to molting.

1, water temperature. At the seedling stage of Penaeus vannamei, when the water temperature is 28℃, it takes 30 ~ 40 hours to molt/kloc-0 per time. The molting of Penaeus vannamei is also related to the lack of full moon. When there is a full moon on the first day of the lunar calendar or in May, prawns shed a lot. The number of prawns weighing more than 15g molts on the first day of the first lunar month or the fifth day around the fifteenth lunar month accounts for 45% ~ 73% of the total number.

2. Environmental factors and nutrition. The main reasons for molting of Penaeus vannamei are related to environmental factors and nutrient intake of Penaeus vannamei. As far as environmental factors are concerned, low salinity and high water temperature will increase the number of molting. Changes in the reproductive environment or the use of chemical drugs can also cause urgency and stimulate molting. Furthermore, whether the nutrition supply is balanced is also related to whether the molting is smooth. Every molting of prawns is a big test for their growth. There are two common problems: first, when the molting shell is weak, it is eaten by other prawns; Second, the oxygen absorption rate is low when molting. If it is not smooth, it may cause hypoxia complications and die.

The growth rate of Penaeus vannamei is faster. Under the conditions of salinity of 20 ‰ ~ 40 ‰, water temperature of 30℃ ~ 32℃ and no feeding, the average weight of each prawn can reach 40 grams within 180 days, and the body length will increase from 1 cm to more than 14 cm.

Under pond culture conditions, the ovary of Penaeus vannamei is not easy to mature. However, in the natural sea area, when the length of the breastplate reaches about 40 mm, individuals will be pregnant with eggs.

Generally, it takes more than 12 weeks for a female to mature, and the average life span can be at least 32 months.

Five, eating habits

Traditionally, shrimp is regarded as saprophytic omnivore, but the latest research report shows that shrimp should be carnivorous in nature, feeding on small crustaceans or copepods. The results of Hawaii laboratory show that the growth of Penaeus vannamei in a completely clear laboratory is only 50% of that of outdoor artificial culture. Because the substrate of outdoor culture pond is loam and the water is rich in algae and microorganisms, the growth rate of Penaeus vannamei cultured in outdoor culture pond is faster than that in laboratory.

The nutritional requirements of Penaeus vannamei are not high. In artificial compound feed, the content of protein can reach 25% ~ 30%, which is better than other prawns. In the artificial compound feed, the content of protein is high, but its growth is poor, because prawns have a certain absorption capacity for protein, beyond a certain range, which not only increases the burden in the body, but also affects the environment. According to research, soybean meal is a palatable feed ingredient for Penaeus vannamei, and its dosage can be as high as 53% ~ 75%. The weight gain rate of Penaeus vannamei fed with 53% and 68% soybean meal was better than that of Penaeus vannamei fed with only 30% soybean meal.

In terms of feeding, although the wild Penaeus vannamei in nature does not actively seek food, practice shows that Penaeus vannamei will eat if fed during the day, because it is stimulated by feed at close range. It was also found that the growth rate of Penaeus vannamei in culture ponds was related to the feeding times, and the more feeding times, the faster the growth of Penaeus vannamei. When feeding, feed 25% ~ 35% during the day and 65% ~ 75% at night, which is the most ideal ratio.

The curing efficiency of Penaeus vannamei to feed is high, and the food intake accounts for about 5% of its weight under normal growth conditions. However, in the reproductive period, especially in the middle and late stages of ovarian development, the food intake will increase significantly, usually 3 to 5 times that of the normal growth period. In the culture of Penaeus vannamei, the expensive animal raw materials can be replaced by plant raw materials, thus greatly saving the feed cost and shrimp culture cost.

Six, reproductive habits

1, reproductive characteristics. The breeding period of Penaeus vannamei is long, and brooding parent shrimp can be seen in the main distribution areas all year round, but the breeding period of parent shrimp in different distribution areas is not completely consistent. For example, the breeding peak on the northern coast of Ecuador generally occurs from April to September. Shrimp seedlings appear in large numbers along the coast from March every year, and the duration can be as long as 8 months. The distribution can sometimes be extended to san pablo Bay in the south, which is the golden season for local shrimp catching, while the breeding peak in the central coastal areas of southern Peru is generally from 65438+February to April of the following year.

Penaeus vannamei belongs to the open seminal vesicle type, and its reproductive characteristics are quite different from those of the closed seminal vesicle.

Open (e.g. Penaeus vannamei):

Molting (female shrimp) → maturity → mating (fertilization) → spawning → hatching.

Closed (e.g. China prawn):

Molting (female shrimp) → mating → maturity → spawning (fertilization) → hatching.

However, the open seminal vesicles and pods are easy to fall off, so it is difficult to raise seedlings. The oviposition process of open seminal vesicle type is first mature and then mate, while that of closed seminal vesicle type is first mate and then mature. Therefore, the mating and spawning forms of the two shrimps are slightly different.

2. mating. The mating of Penaeus vannamei occurs at sunset, usually a few hours or more before the female lays eggs, and most of them are within 2 hours before laying eggs. Mature females before mating do not need to molt. In the process of mating, courtship occurs first, the male shrimp approaches the female shrimp and chases the female shrimp, and then lives under the female shrimp for synchronous swimming. Then the female shrimp turns up, and the abdomen of the male and female shrimp is opposite, and the head and tail are the same, but occasionally the head and tail are upside down. The male shrimp hugs the female shrimp, releases the sperm pod and sticks to the position between the third pair of feet and the fifth pair of feet of the female shrimp. If the mating fails, the male shrimp will immediately turn around and repeat the above actions until the mating is successful. Male shrimp can also chase female shrimp with immature ovaries, but only mature female shrimp can accept mating behavior.

Fresh sperm pods are very sticky in seawater, and it is easy to stick to female shrimp during mating. Under the condition of reproduction, the probability of successful natural mating is still very low, and the reason is still unclear, which needs further study.

3. The number of eggs laid and pregnant. The mature eggs of Penaeus vannamei are red, but the eggs produced are bean green. The leaves of the head, chest and ovary are all clustered, only the head leaf is a big and curved finger, and the leaves behind it start from the front of the heart, cling to the stomach wall and extend to the front. The ovaries in the abdomen are generally small and wide, and will not droop to the sides of the body when they are fully mature. Generally, the brood size of prawns with a body length of1.4cm is only1.5000 ~1.5000.

Penaeus vannamei, like other prawns, can mature again after ovarian emptying. Spawning interval is 2 ~ 3 days, and the initial breeding period is only about 50 hours. The number of spawning can reach more than ten times, but after three or four times of continuous spawning, it will be accompanied by 1 molting.

The spawning time of Penaeus vannamei is between 9 pm and 3 am. It takes only 1 ~ 2 minutes from spawning to ovarian emptying.

Male sperm pods of Penaeus vannamei can also be formed repeatedly, but the maturity period is long, and it usually takes 20 days from the discharge of the former sperm pod to the full maturity of the latter. However, after unilateral eyestalk removal, the development speed of spermatopod will be obviously accelerated.

Dark (less than 50 Joules) and low temperature (below 20℃) can effectively inhibit ovarian development, especially before the third stage.

Unmatched females can lay eggs normally as long as their ovaries are mature, but the eggs laid cannot hatch.

Desalination culture technology of Penaeus vannamei

Penaeus vannamei has wide adaptability, strong disease resistance, fast growth, low requirement for feed protein content, high meat yield and long survival time out of water, and is an excellent variety for intensive and high-yield cultivation.

I. Basic conditions

1, origin requirements. Choose a place with sufficient water, good water quality, convenient irrigation and drainage, convenient transportation, complete power supply and no pollution source within 3-5 kilometers.

2. Pond requirements. The suitable area of the shrimp pond is 5- 10 mu, rectangular, east-west, with a water depth of about 2.0 meters, a flat bottom, a dike width of not less than 2 meters, and drainage ditches are arranged at both ends of the pond.

3. Mechanical support. Breeding ponds must be equipped with generators and aerators. Generally, the power of aerators per mu of ponds is required to be around 1 kW, that is, each pond should be equipped with 2-5 aerators 1.5 kW or 3 kW. The matching aerator should be combined with impeller aeration, waterwheel aeration or nanotube bottom aeration.

Second, the preliminary preparation

1, dredging the whole pond. In winter, remove weeds and excessive silt from the bottom of the pond, trim the pond, expose the bottom of the pond to the sun, and crack the bottom of the pond.

2, disinfection and sterilization. About one month before sowing, the pond should be cleaned and disinfected with quicklime 100- 150 kg, bleaching powder 15-20 kg or 50 kg of tea seed cake per mu to kill germs and fish eggs. The medicine for clearing the pond, especially quicklime.

3. The shrimp pond is flooded. The medicinal properties of Qingtang medicine disappear, and it can be fed with water about 10 days before stocking. But before the water enters the shrimp pond, it is necessary to observe whether there are filamentous algae in the pond. If there is, the high-grade water in the pond is about 10 cm, and then the whole pond is splashed with clean water to kill filamentous algae. This can achieve better fertilizer and water effect. When entering the water, you must also do:

A filter screen is arranged at the water inlet. The filter screen adopts 60 mesh nylon mesh cloth or nylon mesh wire, and the mesh length is more than 2 meters, depending on the diameter of the water inlet pump.

Grasp the water inflow scale. 40-50 cm is suitable for the first water inflow, so as to cultivate bait organisms through fertilization, and then gradually raise the water level, and the water level will reach 80- 100 cm when stocking.

4. Cultivate bait organisms. Cultivating and breeding bait organisms (basic bait) in shrimp ponds is an effective measure to solve the palatable bait and accelerate the growth of shrimp after shrimp seedlings enter the ponds, and it is also one of the effective ways to make full use of the natural productivity of shrimp ponds and reduce the cost of shrimp culture. Basic food organisms have become an indispensable production link in the breeding process because of their advantages such as fast reproduction speed, simple and feasible culture method and obvious nutritional effect. Practice shows that if the basic bait is rich, shrimp seedlings will survive and grow quickly after entering the pool. The method of fertilization in shrimp ponds is as follows:

Use organic fertilizer to fertilize water: the organic fertilizer used must be fully fermented, and the dosage depends on the environmental conditions at the bottom of the pool. Generally, the dosage per mu is about 25 kg, and the specific dosage depends on the fatness of the pond. But before use, it is best to use lime to kill insects and disinfect to avoid pests.

Ammonium bicarbonate phosphate water: the dosage is about 20kg, and the ratio of ammonium bicarbonate to phosphate fertilizer is 3: 1.

Compound organic fertilizer: such as special organic fertilizer for Penaeus vannamei. The dosage is 20-40 kg per mu, and the effect is faster and better when combined with compound fertilizer.

Other varieties: such as bio-fertilizer and active fertilizer and aqua which can be bought in the market.

Description: Generally speaking, organic fertilizer, chemical fertilizer, biological fertilizer, etc. Organic use has the best effect. The specific dosage depends on the basic situation of the pond, the degree of fatness and thinness, and the source water quality.

After fertilization and watering, the water color is yellow, green or brown, and the transparency is 30-40 cm.

Third, shrimp fry stocking

1, shrimp selection.

Select improved shrimp seedlings. You should choose the first or second generation seedlings, not the seedlings with degraded quality, especially SPF seedlings.

Choose healthy shrimp. In the process of raising seedlings, there has never been any disease or stress reaction, that is, there has never been a phenomenon of dead seedlings. The selected shrimp seedlings require healthy seedlings, good vitality, strong physique, complete appendages, clean body surface and appendages, normal body shape, neat specifications and full and clear gastrointestinal tract.

Specification: 1 cm.

Salinity: it is required to be below 3‰, which is basically close to the stocking pond.

2. Test the seedlings. Seedlings must be tested before stocking. First, put the water from the culture pond into the seedling pot, and then filter the selected desalted seedlings and put them in. Observe 12 hours or more. If there are no dead seedlings, release them. If there is a phenomenon of dead seedlings, the reasons should be found from salinity, PH, ammonia nitrogen, nitrite and so on.

3. lead time. It is better to choose the water temperature above 23℃, that is, it is more suitable to put seedlings in our area from early May to early June.

4. stocking density. Generally, it is appropriate to put 40,000-60,000 tails per mu. Seedlings should be planted in sunny morning or evening, and should not be planted in the sun at noon or rainy day.

5. Water quality requirements.

Water color: yellow-green or brown is preferred;

Transparency: 30-40 cm;

PH value, 7.8-9.0;

Salinity: the salinity of the pond should be basically close to that of the nursery pond;

Water temperature: the temperature difference should not exceed 2℃. If there is a big difference, try to adjust it. Generally, when shrimp seedlings are transported to the shrimp pond, the seedling bags should be put into the shrimp pond 10- 15 minutes. After the water temperature is balanced, the shrimp seedling bags should be opened and put into the pond, which is conducive to improving the survival rate of shrimp seedlings.

Fourth, feeding technology.

1, feed selection. Choose pollution-free feed for Penaeus vannamei.

2. Feed requirements. The food requirements of Penaeus vannamei at different growth stages are slightly different. During the juvenile shrimp period within 6 cm, the requirements for protein and unsaturated fatty acids are higher, and the content of protein in feed is generally required to be above 38%; 6- 10 cm shrimp can reduce protein and unsaturated fatty acids, and the content of protein can be between 36-38%. Generally, the content of protein in 10 cm adult shrimp is 32-36%.

3. Control of feed rate. The dosage of bait should be determined according to the weather, survival rate, pond storage and residual bait.

Within half a month after the shrimp seedlings are put into the pond, a small amount of open feed or broken feed can be fed to Penaeus vannamei;

Young shrimp stage: 1 feed, with protein content above 38%, and the feeding time is controlled within 2-3 hours;

Mid-shrimp stage: when feeding No.2 feed, the content of protein can be between 36-38%, and the finishing time should be controlled at 1-2 hours;

Adult stage: Feed No.3, with protein content of 32-36%, and the feeding time should be controlled at about 1 hour.

3. Feeding skills.

Adhere to frequent feeding and less feeding, and the number of feedings per day is generally not less than 2 times. If feeding twice, the feeding time is: 5-8 am and 4-6 pm;

When the water temperature is below 15℃ or above 32℃, feed less or stop feeding;

Feed more in windy and warm days, feed less or stop feeding when thunderstorm, rainstorm and cold current strike (cooling above 5℃);

Feed shrimp less on the day of molting and more after molting 1 day;

Feed more when the water quality is good, and feed less or stop feeding when the water quality becomes worse.

Verb (abbreviation of verb) water quality management

The water environment in shrimp ponds directly affects the growth and survival of Penaeus vannamei, and shrimp culture is hydroponics. If the water quality can be effectively treated and the living environment of shrimp is good, shrimp will be healthy and grow rapidly. The pollutants in the water environment exceed the tolerance of prawns, which will cause poor growth and chronic poisoning of prawns, as well as decreased physiological function, induced diseases, abnormal activity and behavior, poisoning death and so on. Therefore, water quality management plays a very important role in shrimp culture, and the quality of water quality is affected by water source, climate, aquatic organisms, residual bait and biological excreta. These effects are sometimes not only single, but also comprehensive. Therefore, we must pay attention to control various influencing factors, make the water quality stable and good, and promote the healthy growth of prawns. Do a good job:

1. Control water color: The ideal water color for Penaeus vannamei culture is yellow-green or yellow-brown. The transparency should be controlled between 30-40cm in the early stage of culture and about 30 cm in the middle and late stage. Fresh water should be added every 7- 10 days, preferably every 10- 15 days, so as to improve water quality and reduce organic biological content, ammonia nitrogen, nitrite content and organic oxygen consumption.

2. Adjusting PH value: The most suitable PH value of Penaeus vannamei is 7.8-8.6, and the low pH value should be adjusted with quicklime, preferably not exceeding 9.0.

3. Improving the bottom material: With the growth of shrimp and the increase of feed, especially in the middle and late stage of Penaeus vannamei culture, the bottom material environment is relatively poor, so it is necessary to improve the bottom material. If the water quality is too strong or too clear, the sediment environment is often poor, so it is necessary to put some sediment improvers to improve the sediment environment to reduce the adverse effects on Penaeus vannamei.

4. Pay attention to dissolved oxygen in ponds: In the process of Penaeus vannamei culture, the demand for dissolved oxygen in water is increasing with the growth of Penaeus vannamei, so in the early stage of culture, the aerator is started intermittently according to the water quality. In the future, with the growth of shrimp, the start-up time should be gradually extended to ensure that the dissolved oxygen in the pond is above 5 mg/L and the dissolved oxygen in the bottom of the pond is above 3 mg/L. If necessary, the bottom aerator should be put into operation to increase the dissolved oxygen in the whole pond.

5. Start the aerator at the right time: start it for 2-3 hours in rainy days and when adding water within one month after sowing, which can better cultivate good water quality; After one month, start the machine for 2-4 hours at noon and night every sunny day, and gradually extend the start-up time with the growth of shrimp. In rainy days, poor water quality and other weather, the start-up time should be extended or started 24 hours, which is conducive to maintaining stable and good water quality and preventing white shrimp from floating head due to lack of oxygen.

6. Do a good job in water quality measurement: the main measurement indicators are PH value, dissolved oxygen, ammonia nitrogen, nitrite and transparency. Once some 1 indicators have problems, effective measures should be taken in time.

Six, disease prevention technology

The occurrence of diseases in Penaeus vannamei is very complicated. On the basis of desilting and disinfection in ponds, stocking healthy shrimps and feeding high-quality feed reasonably, the following measures should be taken:

1, enhance the compressive strength. Spraying "stress king" in the pond and adding shrimp multivitamins and Nutrilite to the feed can enhance the anti-stress and disease resistance of Penaeus vannamei.

2. Solve the problem of insufficient dissolved oxygen in the pond. Start the aerator and put it in. Increase the dissolved oxygen in the upper and lower water bodies to prevent the floating head or dark floating head phenomenon of Penaeus vannamei.

3. Improve the environmental conditions of the pond. Biological agents and matrix modifiers are used to improve the water quality and bottom environment of ponds and maintain the balance between algae and bacteria.

4. Conduct regular water quality tests to maintain good water quality.

5. Drug prevention. Dibromohydantoin, chlorine dioxide and povidone iodine are generally used for water disinfection. Generally, drugs with anti-stress ability are used in internal medicine, such as multivitamin for shrimp, vitamin C and immune polysaccharide.

6, found that sick shrimp, dead shrimp should be fished out in time, immediately check the cause and cause of death, and suit the remedy to the case, or take other effective measures.

Seven. harvest

1, get ready. After 90 days of culture, the fish can be caught when the specifications reach 120/kg. Before fishing, you should make all the preparations for harvesting shrimp in advance.

Do a good job in market research, find out the market situation of shrimp sales, and contact the sales channels;

Ask the local meteorological department about the recent weather conditions and temperature changes;

Carefully and comprehensively check the growth status of prawns in shrimp ponds and the biological carrying capacity of aquaculture water;

Get the shrimp collection tools ready.

2. Fishing. The fishing methods of Penaeus vannamei include cage trapping, net traction and dry pond fishing, but it should be noted that:

Where Litopenaeus vannamei meets the commodity specifications, shrimp should be caught in batches in time, prawns should be caught and shrimps should be kept;

Before the typhoon comes, according to the size of shrimp, it is best to take turns fishing to reduce the shrimp load in the pond;

When the cold wave strikes, the temperature drops sharply (above 8℃), and shrimp can't be caught;

When the water quality suddenly deteriorates or shrimp is abnormal, shrimp should be caught as soon as possible.

Daily management of Penaeus vannamei

The daily management of Penaeus vannamei includes water quality management, bait management, pond patrol management and wintering management.

I. Water quality management

Keep the water level and change the water. It is best not to change water in the early and middle stages of culture. At the initial stage of culture, add a small amount of water for 3-5cm every day until the water level reaches 1.6m, and keep the water level. In the middle and late stage of culture, if the transparency is lower than 20cm or higher than 80cm, it is necessary to change the water as appropriate, slowly add a small amount of water to the upper pond water, and control the daily water change rate at 5- 10cm, and add quicklime at the same time, with the water surface area of 10- 12g/ m2.

Use an aerator. Every 0. 1-0. 15hm (square) shrimp pond is equipped with an impeller aerator with the power of1.5kw. The function of the aerator is not only to increase the dissolved oxygen in the water and promote the decomposition of organic matter, but also to concentrate the organic debris, feces, algae residue and residual bait in the pond and increase the space for shrimp to stay and eat. Under normal circumstances, within 30 days after seeding, it should be turned on twice a day, starting at noon and evening, 1-2 hours. After 30-60 days of culture, the starting time can be extended, preferably 2-3 hours before dawn every day. After 60 days of culture, due to the increase of the total weight of prawns, too much feces are excreted every day, which aggravates the pollution of the water itself. Basically, it needs to be turned on all day to ensure that the oxygen content in the water body is above 5 mg/L.

Using light and bacteria. In the process of culture, high-concentration light and bacteria are used once every 20 days, and the addition amount is 3-4ML per cubic meter of water, which can effectively prevent the deterioration of sediment and the increase of pathogenic microorganisms. It is best to arrange the time of light and bacteria release on the third day after disinfection in shrimp ponds. On the one hand, drug poisoning can be avoided, and on the other hand, microbial ecological balance suitable for shrimp growth can be quickly established after application.

Second, the bait management

Feeding time. Within 30 days after the seedlings are released, the pond water is rich in basic bait and fed twice a day; Feeding white shrimp for 30-60 days, 3-4 times a day; In the later stage, as the number of shrimp individuals reaches more than 8g, the daily feeding amount will increase, so the feeding should be dispersed and the feeding can be increased to 5 times.

Feeding amount. The daily feeding amount of Penaeus vannamei is 7%-9% (less than 3g), 5%-7%(3-6g) and 3%-5% (more than 6g) according to its weight. However, the factors affecting the daily intake of prawns are very complicated. We can take it within 1.5 hours after feeding, or after feeding for two hours, we can randomly collect 80- 100 white shrimps, adjust the feed according to the full feeding rate of 70%, and master the following principles: feed less when molting a lot, feed more one day after molting, and be rainy and lack of oxygen.

Third, the management of patrol ponds.

1. Check the changes of water environment and shrimp activities in the shrimp pond and adjust the water quality in time.

2. Check the feeding situation of the bait table and adjust the feeding amount of the day in time.

3. Observe whether there is lack of oxygen and floating head, replenish fresh water in time and start the aerator if found.

4, check whether the sick shrimp, found that the sick shrimp to take corresponding measures in time.

5. Check the infiltration of shrimp ponds to prevent losses caused by pond collapse.

Fourth, overwintering management.

Water quality control. According to the water quality requirements of Penaeus vannamei, the water color of the pond should be controlled to be green or yellow-brown. This kind of water contains green algae and diatoms, which are natural food organisms for shrimp. The transparency of the pool water should be kept at 30-55cm. If the transparency of the pool water is too large or too small, it can be controlled by fertilization or water transfer. The ph value of the pool water should not be too high, and the oxygen holding capacity should be kept above 5mg/L, and the oxygen holding capacity at the bottom of the pool should be kept above 3mg/L, and the minimum should not be lower than1.2 mg/L. When the oxygen amount is too low, the aerator or or water pump can be turned on for flushing.

Hello. Make sure to eat well. The daily feeding amount is 5%-6% of the shrimp's weight, divided into four times, 1 time in the morning, 1 time at noon and twice at night. The feeding method is to feed evenly along the pool, which can be cast farther during the day and closer at night.