Culture techniques of Cynoglossus semilaevis

Cynoglossus semilaevis grows fast and is large. After years of research and tackling key problems, the artificial breeding technology of Cynoglossus semilaevis has made a breakthrough, and the breeding technology has been successfully applied to production. Cynoglossus semilaevis can be cultured in both high-input factory and low-cost pond. Cynoglossus semilaevis is a newly developed fish species and the first artificially cultured sole species. Now this kind of fish is well recognized in both north and south, and the market price can be sold to 320 yuan/Jin. If calculated in this way, raising Cynoglossus semilaevis 1 10,000 1kg can create an output value of 3 million yuan.

Cynoglossus semilaevis can overwinter at 3℃ and spend the summer at 32℃, which is very suitable for aquaculture in most sea areas of China, from Liaoning in the north to Fujian and Guangdong in the south. Seedling densities are generally 400 ~ 150 /m2 of 8 ~ 10 cm, 100 ~ 60 /m2 of 5 ~ 20cm, and 35 ~ 20 /m2 of 25 ~ 30 cm. In the process of industrial aquaculture, the daily water exchange rate of normal-temperature marine aquaculture is 300-500%, the high temperature in summer is 500-800%, and the low temperature in winter can be reduced to 200-300%. In the process of culture, the bottom of the pond is cleaned once a day, and the fish need to be moved to a clean pond for about one month, and the original bottom and wall of the pond should be cleaned and disinfected by potassium permanganate. Because Cynoglossus semilaevis is slow in foraging and takes a long time to feed, it is mainly fed with granular feed. Fish with different body lengths should be fed with different feeds, 2 ~ 3 times a day, and the daily feeding amount is 2 ~ 3% of the fish's weight. Under the condition of industrial culture, the body length can reach more than 50cm and the weight can reach more than 1Kg after two years, and the economic benefit is very high. Practice has proved that Cynoglossus semilaevis can be popularized in industrial culture.

Because Cynoglossus semilaevis has little activity, it is easy to attach dirt to fish gills, so it requires fresh water, less suspended matter and certain fluctuation of water body. The water transparency of the aquaculture pond is 50cm, and the water depth is above1m. The specification of releasing seedlings in pond culture is about 8cm, and the water temperature 15℃ is better.

Pond culture technology

Cynoglossus semilaevis is not suitable for cage culture because of its life habit of attaching to the wall undercover and its feeding mode below the abdomen, and can only be cultured in ponds and factories. Compared with industrial culture, Cynoglossus semilaevis is more suitable for pond culture.

Pond culture has a certain natural ecological environment, rich biological bait, fast fish growth, high input-output ratio, simple management and operation, easy to be mastered by ordinary farmers and easy to popularize. In recent years, due to the decline of shrimp farming, many shrimp ponds have been idle and abandoned. Through the reform, the culture of Cynoglossus semilaevis has gradually attracted the attention of farmers.

I. Pond conditions

Cynoglossus semilaevis has little activity, and dirt is easy to attach to gills and fish, which affects its normal growth. It is required that the pond water quality is fresh, the suspended matter is less, and the water body fluctuates to some extent. Cynoglossus semilaevis has the habit of settling sand, so it is required that the bottom of the pond should be sand, reef or sediment, and the bottom of the pond should not be muddy, otherwise harmful substances such as hydrogen sulfide and ammonia nitrogen will be produced at the bottom of the pond, which will cause harm to fish if the concentration is too high. Not suitable for the growth of Cynoglossus semilaevis.

The location of the breeding pond is required to be in a place with convenient living and transportation, which is convenient for production, operation and living arrangements. There is no industrial and domestic sewage pollution and harmful substances in the sea area near the aquaculture pond. The pond is close to the open sea, so it is convenient and timely to take water and drain. The bottom of the pool is flat, which is convenient for farming and harvesting.

It is required that the water transparency of aquaculture ponds should be above 50 cm and the pH value of water quality should be stable. With the help of the water pump, the water in the aquaculture pond does not need to be too deep, and the water depth is generally above 0.5 meters. Cynoglossus semilaevis grows fast at high temperature, and the depth of water is beneficial to improve the water temperature in the pond. The dissolved oxygen in the water is more than 5mg/L, the salinity can be 5-37, and it should be close to the seawater in the surrounding sea area, and the pH value of the water is 7.5-8.5. If the water quality is found to be too fat, the pH value is abnormal, and the transparency of the water body is less than 30 cm, it can be adjusted by changing the water.

Preparation before stocking

1. Layout of aquaculture ponds Every year, after fish are caught, the pond water should be drained, sludge and other pollutants deposited at the bottom of the pond should be removed, and dams, sluices and escape nets should be repaired and strengthened. Before entering the water 1 week, 60-80 kg of quicklime or 0/5 kg of bleaching powder 15 kg should be sprinkled on the whole pond every 667 square meters to kill harmful bacteria, parasites and other diseases. 2. Basic organisms in the pond, such as nereis, grubs, small fish, crustaceans, etc. Before the seedlings are put into the pond, they are cultivated by fertilizing the water quality. The basic biological feed is rich, the survival rate of fry is high, and the growth speed of fry is fast, which can reduce the feed input and improve the breeding efficiency.

Cynoglossus semilaevis likes high temperature and low water temperature, which leads to poor feeding and poor growth. It is better to put seedlings when the water temperature is above 65438 05℃. After pruning and disinfection in winter, water and fertilizer can be fed to the culture pond in early April to cultivate benthic bait.

Second, fish farming.

1. Seed quality and specifications There are few wild seeds of Cynoglossus semilaevis, which are basically cultivated artificially. Cynoglossus semilaevis is slender, swims little, and is easy to be invaded by other organisms, so the specifications of pond-cultured seedlings are too small and the survival rate is low. The specification for releasing seedlings in pond culture requires a total length of 15cm and a weight of more than 20g. The seedlings are required to have normal body color, strong physique, no injury, no disease, no deformity, good food intake and strong ability of undercover to attach to the wall. The qualified rate of seedling length and weight should be above 90%, and the disability rate should be below 5%.

2. For the transportation of fry, Cynoglossus semilaevis has a strong ability to attach to the wall, and the transportation container requires a fixed shape and smooth inner wall. It is not advisable to use containers that are easy to deform or have rough inner walls, such as canvas barrels. Otherwise, when the transport water body bumps, the seedlings are easy to be injured, which leads to the decline of the survival rate of culture.

The water temperature and salinity of transport water can be adjusted in advance according to the water environment requirements of aquaculture ponds. The seedlings should stop eating for more than 1 day before transportation. At present, the transportation of fry mainly adopts plastic bags filled with oxygen in foam boxes. The capacity of plastic bags is generally 20 liters, and the water is 1/4- 1/3. The water temperature in the bag depends on the distance and temperature of the road. When the journey is short and the temperature is low, the seedlings can be transported with the water temperature of 15℃- 16℃. When the journey is long and the temperature is high, the water temperature should be lowered to 1 1℃- 12℃, and the fry should be filled with enough oxygen, then the mouth should be tied tightly, put into the foam box, cover it and seal the foam box with adhesive tape. Each bag can hold 80- 100 fish fry of 15cm, and can be transported for 6- 10 hour. When the temperature is high, you can put some ice cubes inside the foam box and outside the plastic bag to prevent the water temperature in the seedling bag from rising during transportation. During transportation, keep it steady to prevent seedlings from being injured due to violent bumps.

Because it is difficult to disinfect the medicinal bath in pond culture, the seedlings are transported back and put directly into the pond for culture. In order to prevent the occurrence of diseases, oxytetracycline can be used for medicinal bath disinfection during transportation, and the concentration is 2 mg/L. When releasing fry, you should try to choose sunny morning or afternoon to avoid strong sunshine, windy and rainy weather at noon.

After the seedlings are transported to the edge of the pond, the water in the culture pond is gradually added into the seedling transport container, and after 5- 10 minutes of water quality transition adaptation, the seedlings are put into the pond. When Cynoglossus semilaevis enters the pond, it immediately lies at the bottom. If seedlings are placed in one place, the density of the bottom around the seedling placement point is too high, which will have adverse effects. Therefore, more points should be selected when releasing seedlings, so that the seedlings are evenly dispersed in the pool, which is beneficial to feeding as soon as possible, adapting to the environment and improving the survival rate.

The release rate of fry is determined according to the length of fry, which is generally 8 cm ~ 10 cm 400 ~ 150/m2; 100 ~ 60 tails/m2 belt15cm ~ 20cm; 35 ~ 20 tails/m2, 25 cm ~ 30 cm; 18 tail ~ 10 tail m2 of 35cm ~ 45cm. Depending on the breeding conditions, the seedling density should be 400-500 plants /667 m2. If the water exchange conditions are good, the pond with rich bait organisms can increase the culture density accordingly. The stocking density of Cynoglossus semilaevis should not be too high in ponds with poor water exchange conditions and poor bait organisms, otherwise the growth rate of Cynoglossus semilaevis will be slow, the reproductive cycle will be prolonged, the morbidity and mortality will increase, and the reproductive efficiency will be poor.

Third, feeding management.

Cynoglossus semilaevis

1. Water quality management In the northern winter low temperature season, the pond water temperature is lower than 3℃, so it is difficult for Cynoglossus semilaevis to survive at low temperature, which is not suitable for culture. It is necessary to move the fish into the indoor workshop for wintering preservation. The pond culture of Cynoglossus semilaevis mainly uses the high water temperature season from spring to autumn. Water quality management should be adjusted with seasonal changes. The water depth can be kept at 0.5- 1 m before summer. If conditions permit, the amount of water exchange should be increased as much as possible to keep the pond water fresh and stable. After summer, the water level should be raised relatively, and the water depth should be kept above 1 m, which is conducive to maintaining the water temperature in the pond and reducing the cooling effect of cold air. In the south, semi-smooth tongue pond culture can be carried out all year round, but in the high temperature season in summer, the water level and depth of the pond should be raised as much as possible, and the water temperature at the bottom of the pond should be kept relatively low, which is conducive to safely passing through the high temperature season.

The water temperature in natural sea area is relatively stable, which is lower than the pond water temperature in summer and higher than the pond water temperature in winter. In ponds with good water intake and drainage conditions, the water temperature in ponds can be adjusted by increasing the amount of water exchange.

2. Feed feeding in the process of culture, mainly hard pellet feed, supplemented by feed fish. After the fry enter the pond, they can be fed after 2-3 days of stability. Start feeding, mainly fresh feed fish, cut into pieces and feed. After 1 week, it can be domesticated and fed with feed. The dosage of bait should be adjusted according to the feeding situation, weather, water quality environment, etc., generally, it is 1%-2% of the total fish. Cynoglossus semilaevis has scattered feeding habits and does not compete for food in groups. It should be fed evenly as far as possible and not concentrated in one place, so as to avoid concentration of residual feed and deterioration of the bottom of the pond. Always observe the fish's food intake, satiety and residual bait, and flexibly control the feeding amount. The feeding amount should be slightly insufficient, not excessive. When the water temperature is low, you should eat less or not, and when the water quality is poor, you should eat less. Feed twice a day, morning and evening 1 time. Feed at 5-6 o'clock before sunrise every morning and at 4-5 o'clock in the evening. The quality of feed must be guaranteed, and the feed fish that is spoiled and polluted should not be fed.

3. Daily management Cynoglossus semilaevis is a warm fish with high water temperature, fast growth and metabolism, good water quality and high dissolved oxygen content, which is helpful to food digestion and improve food intake rate. When the water temperature is suitable, change as much water as possible. Not only the water quality is improved, but also the biological bait is increased, and the breeding efficiency is improved. Reasonable arrangement of water change time according to tidal time. Patrol the pond every day. If the water color is abnormal, it is necessary to transfer water in time. It is necessary to check the food intake of fish regularly in order to adjust the food intake. When the fish's behavior is abnormal, analyze the reasons or consult relevant technicians to find countermeasures; When sick fish are found, they should be fished out in time for diagnosis and corresponding treatment. Water temperature and air temperature should be measured and recorded every day, so as to know the changes of climate and environment in time and take corresponding management measures.

Cynoglossus semilaevis has a flat body and likes to swim against the current. When there is a gap in the water inlet or a hole in the escape net, the fish will escape with the current. Check whether the escape net at the water inlet is damaged and whether there are gaps around the net frame. When problems are found, they should be fixed in time.

4. Prevention of diseases Prevention of fish diseases in ponds focuses on prevention. Improve the water quality by increasing the exchange water, and disinfect the water regularly, such as spraying quicklime water (100- 150mg/L), bleaching powder (1mg/L), copper sulfate (0.5mg/L) and so on. When it is found that the feeding situation is declining, feed it in time. The dosage of oxytetracycline as bait is 0.2%-0.3%, and 5-7 days is a course of treatment.

Cynoglossus semilaevis is a new species, and there has never been a serious disease epidemic in the breeding process. General bacterial and parasitic diseases can be treated with stone soles. The unique diseases in the breeding process are rotten tail and bleeding.

(1) rotten tail disease

Time of onset: it can occur in the whole process of breeding.

The main symptoms: the tail fin of the sick fish is rotten, the end is white, the skin and muscles at the wound are congested or inflamed, and then gradually spread to the front of the fish, even reaching 1/5- 1/4 of the body length. The death of fish is not serious, and the food intake has not changed significantly. When the environmental conditions are improved and the feed is nutritious, the eroded parts can heal themselves. The etiology and pathogen of rotten tail disease are unknown, which may be related to malnutrition.

Prevention and control measures: improve water quality, change fresh water frequently, improve feed quality and enrich feed nutrients. Take out the sick fish and take a 5 mg/L oxytetracycline bath to prevent bacterial infection in the wound.

(2) Hemorrhagic diseases

Time of onset: it can occur in the whole process of breeding.

Main symptoms: redness of fin, skin and subscale, fin thickening, untidy body surface, mucus secretion and adhesion of various pollutants. When the fish body is serious, it is red in a large area, and the body surface and fin base bleed. Fish don't eat, which leads to death.

Prevention and control measures: improve water quality conditions and change fresh water frequently. Spraying 100- 150mg/L quicklime water in the whole pond and feeding 0.2%-0.3% oxytetracycline bait for 5-7 days is a course of treatment.

5. Lighting requirements

Cynoglossus semilaevis likes poor lighting conditions, and it can still feed by smell without turning on the light at night.

Cynoglossus semilaevis

Fourth, cultivate the ability to catch Cynoglossus semilaevis, dive in the sand and go undercover. It is timid by nature and easily frightened. After being frightened, it is difficult to catch it with your hands. It is difficult to catch fish simply by releasing water or pulling nets, and it is also harmful to fish. The main ways of aquaculture and fishing are drainage and trawling. First, the water level in the pond is lowered, and after the fish are collected with a net, most of the fish in the pond can be caught manually with a net, and then the water in the pond is drained. Fishermen wear water trousers to enter the pond, then catch the fish with nets and put them in the container for fish.

When fishing, we should pay attention to the following aspects: ① Choose sunny days to work, otherwise it will be difficult for wet vehicles to work in rainy days, and the temperature will be too low when the cold current comes, which will easily frostbite the fish; (2) When the pond culture area is large and no fish can be caught 1 day, pay attention to replenish water and change water during the intermission to prevent fish from dying due to the deterioration of water quality; (3) Because Cynoglossus semilaevis only shows two eyes when diving in the sand, the pool water is turbid when fishing, and the fish body can't be seen clearly. Fishermen should be careful when walking, lest they die by stepping on the fish.

Polyculture techniques of prawns in ponds in China.

Proper mixed culture of China shrimp in Cynoglossus semilaevis culture pond, feeding on fish scraps, not only saves bait but also improves the bottom environment, achieving the effect of double harvest of fish and shrimp, with broad prospects.

1 Selection of culture pond

1. 1 water source conditions

Choose a place with sufficient water, stable tidal current, no pollution, fresh water quality, less suspended matter and convenient transportation; Salinity is 15 ‰ ~ 34 ‰.

1.2 culture pond conditions

Separate water inlet and drainage channels to avoid water pollution in aquaculture; There is no leakage in the pond, and the bottom material of the pond is preferably sand bottom, sand mud bottom or sediment bottom, which is beneficial for fish to lurk in the bottom and dive in the sand. The size of the culture pond is 3 ~ 10 mu, and the existing shrimp culture pond can also be modified. The shape of the aquaculture pond should be rectangular or long, the average water depth should be above 1.2m, and it is equipped with a drainage gate, so that the water can be discharged quickly.

2. Preparation before seedling raising

2. 1 pool arrangement

Before stocking fry, the bottom of the pond should be ploughed, exposed and renovated; The bottom of the pool should be drained smoothly, and finally the bottom should be washed repeatedly.

2.2 Disinfection and pest control

Before the fry are put in, the culture pond should be disinfected. Commonly used disinfection drugs include quicklime (generally 350 ~ 400 mg/L water), bleaching powder (containing 25% ~ 30% available chlorine, generally 50 ~ 60 mg/L), chlorine dioxide (generally 1 mg/L) and tea seed cake (generally 1mg/L).

2.3 Water fertilization to cultivate bait organisms

Before the seedlings are released 10 ~ 15d, the water is filtered by a 60 ~ 80 mesh screen for 50 ~ 60 cm, and the bait organisms are fertilized and cultivated. Fertilizers can be selected according to local water quality. Use inorganic fertilizers, such as urea, ammonium sulfate, ammonium bicarbonate, calcium superphosphate, diammonium phosphate, etc. 2 ~ 5mg/L of nitrogen fertilizer and 0.2 ~ 0.5mg/L of phosphorus fertilizer; Organic fertilizer is used to ferment and disinfect the feces of chickens, pigs, sheep, cattle, etc., generally 100 ~ 200mg/L water, which is used to cultivate plankton in ponds, such as nereis, slugs, cladocera, copepods, etc., so that fish and shrimp fry can eat palatable and nutritious bait as soon as they enter the pond. Fertilizing fertilizer and water is an important technical measure to improve the survival rate of seedlings, promote growth, reduce bait input and improve breeding efficiency. Through fertilization, the water in the pond is yellow-green, yellow-brown, and new water or topdressing is added according to the water color in the pond.

3. fry stocking

3. 1 stocking Cynoglossus semilaevis

3. 1. 1 Fish species source: fish species cultivated artificially or caught in natural waters.

3. 1.2 The quality of fingerlings requires that they should be physically strong, with normal body color, smooth body surface, no injury, no disease, no deformity, good food intake, strong ability to bury the bottom and wall, and the total length should be above 10cm; Fish caught in natural sea areas should be domesticated and raised artificially in indoor nursery ponds or aquaculture ponds, and released after domestication and feeding for a period of time (generally 20-30 days).

3. 1.3 stocking time and conditions of fish species in Shandong coastal areas, the stocking time is generally from the end of April to the beginning of May; The water temperature of the pool must be kept above 14℃, with a water depth of 50 ~ 60 cm and a transparency of 30 ~ 40 cm.

3. 1.4 before disinfection and stocking of fish species, the fish must be disinfected to prevent them from entering the pool with diseases. Generally, the method of medicinal bath is adopted. Commonly used drugs, dosage and bath time are: 40 ~ 50mg/L PVP-I (containing available iodine10%)15 ~ 20min; 1.5 ~ 20mg/L potassium permanganate 5 ~10min; 0.25 ~ 0.3 mg/L formaldehyde 1.5 ~ 20 minutes; The concentration and time of medicinal bath should be flexibly controlled according to the size and water temperature of the fish species, and the severity of stress on the fish species of Cynoglossus Cynoglossus should prevail. When disinfecting fry, the action should be quick and light to prevent fish from being damaged, and the number of medicated baths should not be too many at a time.

Fish stocking should choose sunny and windless weather. The place where the fry enter the water should be in the lee of the sun, and the container for the fry should be tilted in the water of the breeding pond, so that the fry can swim in the pond by themselves.

3. 1.5 For fish with total length greater than 10cm, the stocking density is 800 ~ 1000 fish per mu.

3.2 Stocking of prawn fry in China

3.2. 1 Shrimp seedlings mainly come from artificially cultivated shrimp seedlings.

3.2.2 The quality of shrimp requires that the shrimp should be healthy, vigorous, robust, neat in specifications, fresh and tender in color, smooth in surface, free from trauma, germs and diseases, and the total length should be above 1cm.

3.2.3 Time and conditions for stocking shrimp fry. The release time of shrimp seedlings in Shandong coastal areas is generally May-June; The water temperature of pond water must be kept stable above 65438 06℃, the salinity and temperature difference between pond water and seedling water should not exceed 5, the pH value of pond water should be 7.8 ~ 8.6, the climate is suitable, and there is no strong wind, rainstorm and cold current. Seedlings should be placed in the upwind of deep pool water, not in the upwind, but in shallow water or near the gate.

3.2.4 Stocking density of shrimp fry: the total length of shrimp fry is more than 65438±0cm, and the stocking density is 2000 ~ 3000 per mu.

4 feeding management

4. 1 water quality management

Cynoglossus semilaevis and Penaeus China are polyculture in northern ponds, mainly in the hot season from spring to autumn. The management of water quality should be adjusted with the change of seasons. Before summer, the water depth is about1m. If conditions permit, change water as much as possible to keep the pond fresh and stable. After entering summer, making the water level in the pond reach the highest level is conducive to maintaining the water temperature in the pond and reducing the cooling effect of cold air.

In the south, Cynoglossus semilaevis and China shrimp can be mixed in ponds all year round. Only in the high temperature season in summer, the water level and depth of the pond should be raised as much as possible, fresh water should be replenished in the morning and evening, and the water temperature at the bottom of the pond should be kept relatively low, so as to help the cultured fish and shrimp survive the high temperature season safely.

4.2 Feed supply

In the process of breeding, granular compound feed is mainly used, supplemented by fresh feed fish, such as jade fish and scaly fish. Fish and shrimp seedlings can be fed after 2 ~ 3 days of stabilization. Start feeding, mainly fresh small fish, cut into pieces and feed quickly. 15 ~ 20 days later, it can be domesticated and fed with granular compound feed. The feeding amount of bait should be properly adjusted according to the eating situation of fish and shrimp, weather and water quality environment. The feeding amount in the early stage is generally 5% ~ 8% of the weight of fish and shrimp; 2% ~ 3% of the weight of fish and shrimp in the later stage. Cynoglossus semilaevis feeding is scattered, so it should be fed evenly as far as possible, not concentrated in one place, so as to avoid the concentration of residual bait and the deterioration of the bottom of the pool. It is necessary to constantly observe the feeding and satiety of fish and shrimp and the amount of residual bait, and flexibly control the feeding amount of bait. Feed twice a day from 6: 00 to 7: 00 in the morning and 16:00- 17:00 in the evening. The quality of the bait must be guaranteed.

4.3 Daily management

4.3. 1 Strengthen the detection and management of water environment in aquaculture ponds, and regularly detect seawater salinity, chemical oxygen consumption, red tide biomass, feed composition and density, etc. The management of water quality should be checked and observed frequently, and the old water should be discharged in time according to the water quality situation, and the new water should be supplemented to effectively improve the water quality conditions.

4.3.2 Insist on patrolling the pond every morning, noon and evening, observe the dynamics of fish and shrimp and the change of pond water, and take corresponding measures in time when problems are found.

4.3.3 Measure the growth of fish and shrimp regularly. Every 15 days, 20 ~ 30 fish and 50 ~ 100 prawns were randomly sampled with nets to check their food intake, measure their total length and body length, analyze their growth, and adjust management measures appropriately according to specific conditions.

4.3.4 Strengthen daily management. Be careful in your daily work to prevent fish and shrimp from being injured. Pay attention to the environmental sanitation of the aquaculture pond, diligently remove the miscellaneous algae in the pond, and diligently remove the weeds beside the pond; If sick fish, shrimp or dead fish and shrimp are found, they should be fished out in time. After examining and analyzing the causes of diseases and deaths, they will be destroyed in a centralized way, and corresponding measures will be taken according to the severity of diseases. In severe cases, the diseased fish and shrimp ponds should be isolated from other ponds.

5 Prevention and control of diseases

Prevention is the key to prevent fish and shrimp diseases. First, through a series of ecological disease prevention measures, such as increasing water exchange, increasing dissolved oxygen, fertilizing, topdressing, and regularly disinfecting water bodies (such as spraying quicklime, bleaching powder, calcium peroxide, etc.). ), create a good ecological environment for fish and shrimp, so that fish and shrimp are not sick or less sick; Second, feed high-quality compound bait. Feed compound bait containing various vitamins, polysaccharides, allicin, seaweed powder, cod liver oil and other ingredients regularly to enhance the disease resistance of fish and shrimp and effectively prevent the invasion of diseases.

6 harvest

6. 1 Harvest time

Fishing time should be flexibly determined according to market demand, price, fish and shrimp specifications, sanitary conditions, tidal conditions and water temperature changes. Under normal circumstances, fish and shrimp should leave the pond before the water temperature drops to 12℃. Fish can be moved indoors for temporary culture. If the fish meets the specifications, it will be sold in time according to market demand. If it can't meet the specifications, it can be cultivated indoors.

6.2 Feeding specifications

After fish and shrimp culture 150 ~ 180 d, the average individual weight of Cynoglossus semilaevis was over 300g, and the survival rate was over 60%. The average weight of China prawns can reach more than 35g, and the survival rate can reach more than 25%.

6.3 harvesting methods

More than 80% can be harvested by net fishing and shrimp shoveling. Finally, the remaining fish and shrimp can be harvested through a net with a gate. No matter what harvesting method is adopted, it should be carefully operated to avoid fish and shrimp injury and ensure a high survival rate.

Effect of vitamin C supplementation in feed on juvenile Cynoglossus semilaevis

Six kinds of experimental diets were made by adding 0, 10, 50, 150, 450 and 1 500mg/kg vitamin C (in the form of multivitamin C) to the basic diet of Cynoglossus semilaevis. Six groups of Cynoglossus semilaevis with initial body mass of (4.265438 0.02) g (experiment ⅰ) and (65438 0.65438 0.06.93 0.965438 0) g (experiment ⅱ) were fed for 65438 0 weeks. Three replicates were set in each group, with 60 fish in each replicate (experiment ⅰ) and 8 fish in each replicate (experiment ⅱ), to study the effects of vitamin C in feed on the survival, growth and ascorbic acid content in tissues of Cynoglossus semilaevis larvae. The results showed that the survival rate, weight gain rate, specific growth rate and feed conversion rate of Cynoglossus semilaevis increased with the increase of vitamin C content in feed, but the difference was not significant (P & gt0.05). With the increase of vitamin C content in feed, ascorbic acid content in liver, kidney and muscle increased significantly (P 0.05), but vitamin C in feed had no significant effect on weight gain rate and specific growth rate (P & gt0.05). When the added amount of vitamin C in feed exceeded 50mg/kg, the content of ascorbic acid in liver, kidney and muscle increased significantly with the added amount, which was higher than that in control group (P