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Oyster farming methods (key points of oyster farming technology)

Xinxiang Excellent Vegetable Research Institute 20:30 Editor: Lu Yi 269 Reads

1. Key points of oyster farming technology

The breeding site should be selected in the sea area with small waves, stable water quality, no industrial pollution, muddy or silty bottom, water depth above 8m, stable water temperature, no more than 30℃ in summer, surface flow velocity of about 0.3-0.5m/s, specific gravity between 1.008-1.02. The specific salinity and temperature range depends on the oyster species. For Omi oysters, the suitable temperature range is 10-33℃ and the suitable salinity range is 5-25‰.

For long oysters, the suitable temperature range is 5-28℃, and the suitable salt range is 10-37‰, especially 20-30‰.

2. Oyster farming conditions

How do oysters grow?

Oysters refer to raw oysters, also known as spider oysters, marine molluscs, the meat of which is edible and is a very expensive seafood in restaurants.

Oysters, also known as oysters, oysters, etc., are a type of marine bivalve molluscs that are fixed in life and generally live fixed on rocks in suitable sea areas. There are many species of oysters, which are distributed along the coasts of both north and south my country. The main species suitable for cultivation in southern waters is the pleated oyster; the species suitable for cultivation in northern waters mainly include Pacific oysters and Dalian Bay oysters.

Oysters have different adaptability to various factors in the aquatic environment due to different species, and the differences are even quite large. The suitable salinity range for pleated oysters is 2.2%-2.6%. Higher than 3.0% or lower than 1.0% are not conducive to growth. The suitable water temperature for Pacific oysters is 6-32℃. When the water temperature is higher than 28℃ or lower than 6℃, the growth slows down or stops. It grows fastest when the water temperature is 15-25℃; the suitable salinity range is 0.6%-3.0%, and the optimum is 0.6%-2.6%.

There are many ways to cultivate oysters, including stone-throwing cultivation, bamboo-inserting cultivation, raft-frame cultivation, floating raft cultivation, bottom seeding and proliferation. Due to different cultivation methods, the designed per-acre yield is also very different. Taking the raft-frame cultivation of pleated oysters as an example, rafts are set up at the lower edge of the tidal stream and low tide zone, and oysters are raised on the rafts. Each raft is 50-60 meters long, and a string of oyster seedlings is hung every 30 centimeters, with about 30 pieces in each string; the distance between rafts is 3-4 meters, and 2-2.5 rafts are one acre. Generally, it can be harvested after 7-8 months of cultivation. The harvest season is from January to April. The size of the individual is 7-8 cm in shell length, and the general per-acre yield can reach 6-10 tons (fresh weight with shell).

3. Oyster farming methods

Oyster farming methods

Oysters, also known as oysters, are the richest in zinc among all foods (every 100g of oysters, excluding the weight of the shell, contains 87.1% water and 71.2mg zinc. It is rich in protein zinc and is a good zinc supplement. Oysters live a fixed life from the time they attach themselves to the object and cannot move on their own. They can only open and close their shells. The left shell is fixed, and only the right shell can open and close. They rely on the opening and closing of the right shell to carry out life activities such as breathing, feeding, reproduction, and excretion. When encountering adverse environmental conditions, they close their shells tightly to survive.

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1. Lifestyle

Oysters live a fixed life from the moment they attach themselves to the object they are attached to. They cannot move on their own and can only open and close their shells. The left shell is fixed, and only the right shell can open and close. They rely on the opening and closing of the right shell to carry out life activities such as breathing, feeding, reproduction, and excretion. When encountering adverse environmental conditions, they close their shells tightly to survive. The long oyster is a wide-temperature shellfish that can live in water temperatures of 0-32℃, and the most suitable water temperature for growth is 15-25℃. It also has a wide range of adaptability to salinity, and is distributed in the salinity range of 10-40‰. It grows faster in sea areas with low salinity. Oysters mainly feed on single-celled plankton and organic debris. There is no special regularity in feeding. Generally, feeding is vigorous when the water temperature is 10-25℃, but during the breeding season, the intensity of feeding is relatively weakened.

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2. Reproduction characteristics

When oysters reach one year old, their gonads mature and they begin to reproduce. There are two types of reproduction: larval and oviparous. Long oysters are oviparous and fertilized in vitro. Most long oysters are hermaphroditic, and a small number are hermaphroditic. When the gonads mature, the males are milky white and the females are light yellow. When the water temperature in the natural sea area rises to 16℃, the gonads of long oysters begin to mature, and the peak spawning period is when the water temperature reaches 24-25℃. Oyster spawning is mostly carried out during high tides. When the water temperature is 23℃, the fertilized eggs develop into D-shaped larvae after 20-22 hours. Under the condition of water temperature of 23-26℃, after about 20 days of cultivation, the average shell length of the D-shaped larvae can reach more than 280μm, and 40%-50% of the larvae have eyespots. At this time, the attachment substrate should be placed so that the larvae can metamorphose and attach.

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3. Breeding methods

There are many methods for oyster farming. With the continuous development of farming, new farming methods and technologies are constantly emerging. Among them, the more common ones are bamboo planting, bottom seeding, strip stone and standing stone farming, and hanging farming. Among them, hanging farming is divided into grid type, longline type and raft type. Regardless of the farming method or method, the selection of the breeding site is the key. It should be determined according to the living habits of oysters and the requirements of oysters for environmental factors and within their adaptability range. In addition, the degree of pollution of industrial and agricultural hazardous wastewater should also be considered.

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3.1. Raft culture

Choose sea areas with smooth tides, abundant bait, calm winds and waves, and a water depth of more than 4m as oyster raft culture sites. Oysters in the vicinity of the estuary with low salinity should be cultivated in the vicinity of the river mouth; oysters in Dalian Bay should be cultivated in sea areas far away from the estuary with high salinity; Pacific oysters and pleated oysters are between the two. There are two main cultivation methods: ⑴ Rope culture: suitable for oysters that use shells as a base for fixation. There are two ways to cultivate them: one is to string the shells with oyster seedlings together with ropes, separate them with bamboo tubes of about 250px in the middle, and hang them on the raft frame; the other is to clamp the shells with oyster seedlings in the twisted seam of a polyethylene rope with a diameter of 3 to 87.5px, clamp one shell every 250px, and hang them on the floating raft. Generally, each rope is 2 to 3m long. Rubber tires can also be used to clamp seedlings for hanging culture. ⑵ Net cage culture: scallop net cage culture. Oyster seedlings without anchorage or attached to shells are placed in scallop nets together with shells and raised on floating ropes. Raft culture generally releases 100,000 oyster seedlings per 667 square meters, using shells as seed collectors. About 10,000 shells can be raised per 667 square meters. Oyster seedlings are released from May and June and harvested at the end of the year. The yield per 667 square meters can reach more than 5,000 kg.

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3.2. Tidal flat breeding 3.2.1. Site selection: Tidal flat breeding should be carried out in inner bays with small waves, smooth tides and no pollution. Sandy muddy beach or muddy sandy beach is the best bottom. The tidal area should be located at the lower part of the mid-tidal area and near the low-tidal area. 3.2.2. Seeding season: Generally, mid-March to mid-April is the most suitable time for seedlings. In terms of production, seedlings can be planted in mid-May at the latest.

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3.3. Oyster and shrimp mixed culture 3.3.1. Shrimp pond selection: For shrimp ponds with mixed culture of oysters, the bottom should be muddy or muddy sandy, the water depth should be more than 1.3m, and the average daily water exchange rate should be about 50%. The transparency should be controlled at 40-1250px in the early stage, and 50-1500px in the middle and late stages. 3.3.2. Site preparation: Before stocking the seedlings, the silt should be thoroughly cleared, and the bottom of the pond where the oyster seedlings are planted should be leveled and compacted with tools such as bulldozers, which should be slightly convex and slightly higher than the surrounding bottom surface to prevent the oyster seedlings from sinking and being buried in the silt and dying. 3.3.3. Seeding: Under the premise of ensuring the normal shrimp stocking density, the seeding amount of oyster seedlings should be about 66703000 grains per 66703000 grains. The seeding time should be selected in early April, and the seedlings should be more than 50px in shell length. The seedling sowing stress should be uniform, and the low-lying areas of the ditch and the feeding area should be avoided. The seedling sowing area accounts for 1/4 to 1/3 of the pond bottom area.

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3.4. Stone throwing aquaculture The stones used as oyster seed collectors now become oyster cultivation equipment. The short-lived Crassostrea gigas can be cultivated locally in the seed collection field; the long-lived Crassostrea gigas must be moved to the cultivation field for cultivation. There are three main cultivation methods: star-shaped, plum-shaped, and determinant: 1. Star-shaped: Oyster stones are placed randomly. 2. Plum-shaped: Generally, 5 to 6 oyster stones form a group. 3. Determinant: The row width is 0.5 to 1m, and the row spacing is 0.6 to 1.5m. Deep-water aquaculture can be left without any management after stone throwing until harvest.

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3.5. Bamboo planting culture uses the method of planting bamboo seedlings to plant the collected oyster seedlings sparsely on the spot. When growing, there are two ways to arrange oyster bamboo: ⑴ Straight planting: 150-179 oyster bamboos are planted in rows, and the row length is 3-5m; or 100-120 oyster bamboos are planted in rows, leaving 2-3 gaps in the middle of the row to facilitate water flow. ⑵ Oblique planting: 23-26 oyster bamboos are planted into a pile, with a bottom width of 45-1500px and a top width of 33-900px. The distance between piles is 20-625px. A row is composed of 5-6 piles, and the distance between rows is about 2.5m. 8,000-10,000 oyster bamboos can be planted per 667O.

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3.6. Bridge culture After collecting seedlings using the bridge method, the stone bars are rearranged, the density is dispersed, and the oysters are grown. Generally, 6 to 7 stone bars form a group, and the groups are connected by stone bars to form a row. The distance between groups is 50 to 1500px, and the distance between rows is 1 to 2m. During the growing period, the shady and sunny sides of the stone bars should be interchanged to ensure that the oysters on both sides grow evenly.

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3.7. Standing rock culture After collecting seedlings in the mid-tidal area using the standing rock method, as long as the seedling quantity is appropriate, it can be left to grow naturally without any management until harvest. This method is mainly used for the culture of Crassostrea gigas.

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3.8. Grid culture This culture method is to set up fixed grids in the inner bay at a depth of 2 to 4 meters, when the wind and waves are calm and the bait is not available. The setting of the grids is the same as that of grid seed collection. Oyster seedlings are mostly fixed on a base such as shells and cement tiles in series, and are hung on the grids in strings. Each string is 1 to 1.5 meters long, and the distance between strings is 0.5 to 1 meter. The culture density should not be too high to prevent the bottom from being touched, so as to avoid the invasion of some benthic pests.

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4. Management during the aquaculture period 4.1. Turning the stones: This is to move the position of the oyster stones. Turning the stones can prevent the oysters from being suffocated by the mud and can also stir up the floating mud, increase the nutrients in the bait, and promote the growth of the oysters. Generally, the stones are turned 2 to 3 times during the aquaculture period.

4.2. Flood prevention: In the rainy season, attention should be paid to preventing floods from flowing in, or digging ditches to prevent floods, or moving oysters to high-salinity deep-water areas for breeding. 4.3. Overwintering: Dalian Bay oysters and Omi oysters cultured in the north generally have to go through 2 to 3 winter ice periods. Before freezing, an inspection should be conducted, and oysters that may be threatened should be transplanted to deep water to ensure safe wintering. 4.4. Fattening: 1 to 2 months before harvest, oysters should be moved to excellent fattening farms for fattening to achieve the purpose of increasing production. 4.5. Preventing human trampling: Beach-sown oysters can only filter water and feed on the beach. Once they fall into the mud, they cannot live normally and suffocate to death. It is strictly forbidden to trample on the beach at will, and management personnel should walk along the ditch when going to the beach. 4.6. Clear the ditches: Check the drainage ditches regularly to see if they are unobstructed. Try to avoid water accumulation on the beach after low tide to prevent oysters from dying due to high water temperatures, lurking enemies, and deep floating mud.

4.7. Pest control: There are many enemies of oysters, which should be removed when turning over rocks. During the peak breeding period of red snails and litchi snails from July to September, diving should be done to catch their broodstock and egg bags. In the season when crabs are active, management should be strengthened to catch enemies. 4.8. Wind protection: Typhoons are very destructive to aquaculture facilities, and mud and sand are also blown up to bury the anchors and oysters. Therefore, after a typhoon, timely rescue is required, rafts should be repaired, and fallen or buried anchors should be supported.

4. What conditions are required for oyster farming?

The suitable water temperature for oyster growth is 6-32℃. The growth will be slow or stop when the water temperature is above 28℃ or below 6℃. The growth is fastest when the water temperature is 15-25℃. The suitable salinity range is 0.6%-3.0%, and the optimum is 0.6%-2.6%.

Oysters are also one of the most stress-resistant aquatic animals. The changeable environment of the intertidal zone over the past 200 million years has trained oysters to have strong resistance to temperature, salinity, air exposure and common pathogens in the sea. When they are exposed to the water at low tide, they can withstand the hot and dry weather in summer, and can also successfully adapt to the freezing weather in winter. They can survive out of water and in the air for 1 to 2 weeks, or even 1 month.

5. Oyster farming process

Answer: Oysters are wild, shelled molluscs that live on rocks and in the sea. Huishan has no sea, so oysters cannot be farmed.

6. Notes on oyster farming

Oysters are also known as raw oysters. When you buy raw oysters from the market, you need to put them in water. This will help the oysters excrete dirt. In addition, the oysters will not die if they are kept in water, so you can use fresh oysters. Oysters, also known as raw oysters, are the richest in zinc among all foods (every 100g of oysters, excluding the weight of the shell, contains 87.1% water and 71.2mg zinc. It is rich in protein zinc and is a good zinc supplement food. To supplement zinc, you can often eat oysters or protein zinc. It is the whole of oysters (ostreagigastnunb) and its closely related animals of the oyster family (ostreae), and is a marine shell. Oyster farming is suitable in subtropical and tropical coastal areas. my country has a wide distribution, from the Yalu River in the north to Hainan Island in the south, and oysters can be produced along the coast. Oysters are soft-bodied, parasitic animals with shells, and those produced at the junction of salt and fresh water are particularly plump. 1. How to clean oysters Oysters generally do not need to spit out mud and sand. When cleaning oysters, it is best to wear latex gloves, put the oysters in water, and use a brush to clean the mud and sand attached to the oyster shells. If you buy fresh oyster meat, it is often mixed with broken oyster shells or other impurities. Just drop a proper amount of vegetable oil (peanut oil) into it and it will be easier to clean. 2. Soaking First prepare a basin of hot water, dissolve a little baking soda in the hot water, and then soak the dried oysters in the hot water. Soaking will not only make it easier to clean but also remove the odor of the dried oysters. After washing, rinse it with clean water. The dried oysters processed in this way will taste good no matter how you cook them. 3. Precautions for eating oysters 1. If you choose to boil them, you must boil the shells of the oysters completely. It is best to boil them for 3-5 minutes after the shells open. 2. If you want to steam them, wait until the water is completely boiled before putting the oysters in. After the shells are fully opened, steam them for another 4-9 minutes. 3. At the same time, please note that when steaming oysters, try to use a small pot to avoid using a large pot to cook too much at a time, otherwise the oysters may be heated unevenly and some oysters may not be cooked thoroughly. 4. In addition, do not eat oysters that cannot open during the steaming process.

7. Oyster farming technology

First, these white liquids are the tadpoles of male oysters. They will meet the eggs of female oysters and hatch into baby oysters the size of dust particles. In recent years, people have overfished wild oysters, causing their numbers to drop sharply. Therefore, 95% of the oysters we eat now come from oyster farms. People raise oysters in soft king barrels on the seashore. Oysters can start breeding when they are six months old. When the breeding season comes, workers will put oysters in breeding grass with a water temperature of 20 to 30 degrees to swim, so that the female oysters can ovulate. At this time, the female oysters will spray eggs, and the male oysters will spray tadpoles. After 12 hours, the baby oysters will be hatched. When the oysters are born, they will dilute the phytoplankton mixture with seawater and pump it into the oyster container. Because these newly born baby oysters are very small, they cannot be seen with the naked eye, and can only be seen under a microscope.

Second, from the moment they start to hatch, they already have shells and can swim. When they are about half a month old, they will grow to 1/3 mm long, at which time the workers will transfer them to circulating water to give them more food and oxygen. As the oysters grow, the workers will also transfer them to larger bottles, and when they are four to six weeks old, they can go to the oyster farm floating in the harbor. Here, they will be placed in cages filled with circulating water to allow the baby oysters to eat phytoplankton. In the next six weeks or so, their size will grow to about four millimeters, at which time the workers will pack them in plastic soft mesh bags, put them on metal racks, and then suspend the metal racks in the sea, allowing them to live in the sea for three months. As the oysters grow, the workers will also transfer them to larger and larger soft mesh bags.

Third, their average length is about 20 mm now, and in six months, their size will be twice as large as it is now. Then the workers spread them on the seabed. At this time, the harvest is no longer determined by the length, but by the weight of the oysters. When it is time to harvest the oysters, the workers will put down the machine that is responsible for digging in the front and transporting in the back. It will spray a strong stream of water to flush the oysters from the bottom of the sea, put them into the conveyor bag, and then transmit them to the sorting station. The workers pick out the oysters that meet the size standards and put them into baskets. Oysters that do not meet the size standards and other debris will return to the sea. Then the oysters will be placed in a tank filled with ultraviolet sterilized seawater for 24 hours to rinse out all the bacteria. Oysters treated in this way can be eaten raw with more confidence.

8. What conditions are needed to cultivate oysters?

Generally, a small amount of hormones or other drugs are used.

Because if oysters are allowed to grow normally, even if the conditions are good and the nutrients are rich, it will take 15-18 months to harvest.

Oysters are not only a food material, but also a medicinal material. They are rich in protein, fat, and many trace elements and vitamins that are needed by the human body. Oysters are especially rich in taurine, which can improve brain function and reduce weight, and promote the decomposition of cholesterol. More and more people are beginning to eat oysters.

9. What are the key points of oyster farming technology?

When triploid oyster seedlings are cultured, the density should not be too dense, otherwise they will grow too fast and easily fall into the sea, causing waste. When the oyster seedlings weigh 1 to 2 taels, it is best to move them to cages, so that the yield will be higher.

Compared with diploid oysters, triploid oysters have obvious advantages. First, the growth rate of triploid oysters is at least 30% to 50% faster than that of diploid oysters. Second, the meat quality of triploid oysters is better than that of diploid oysters, and the economic benefits are higher.

10. Introduction to the key points of oyster farming technology

Oyster farming techniques

1. Growth habits of oysters

Oysters are distributed in tropical and temperate waters, ranging from high seas to more than 10 meters in depth. Oysters are sessile shellfish, generally fixed on shallow sea objects or seaside reefs. Long oysters are wide-temperature shellfish, which can live in water temperatures of 0 to 32°C, and the most suitable water temperature for growth is 15 to 25°C. It also has a wide range of adaptability to salinity, and is distributed in the salinity range of 10 to 40‰. It grows faster in sea areas with low salinity. Oysters mainly feed on single-cell plankton and organic debris. There is no special regularity in feeding. Generally, feeding is vigorous when the water temperature is 10 to 25°C, but during the breeding season, the feeding intensity is relatively weakened.

2. Oyster farming technology

(I) Seedling breeding

Currently, there are two methods of oyster farming: fully artificial seedling cultivation and semi-artificial seed collection.

The operating procedures of fully artificial seed breeding include: temporary rearing and ripening of broodstock, egg collection, hatching and selection, bait and larval cultivation, preparation, processing and release of attachment base, and removal of juvenile spat from the pond; the operating procedures of semi-artificial seed collection include: selection of seed collection site, examination of broodstock gonad development, collection and investigation of planktonic larvae, preparation, processing and release of attachment base, etc.

(II) Breeding methods

1. Raft cultivation

Choose sea areas with smooth tides, abundant bait, calm winds and waves, and a water depth of more than 4m as oyster raft culture sites. Oysters from the Yangtze River should be cultivated near estuaries with low salinity; oysters from Dalian Bay should be cultivated in sea areas far from estuaries with high salinity. There are two main cultivation methods:

(1) Rope culture: Suitable for oysters that use shells as a base for anchoring. There are two ways to cultivate them: one is to string the shells with oyster seedlings together with ropes, separate them with bamboo tubes about 10 cm in the middle, and hang them on the raft; the other is to clamp the shells with oyster seedlings in the twisted seams of polyethylene ropes with a diameter of 3 to 3.5 cm, clamp one shell every 10 cm, and hang them on the floating raft. Generally, each rope is 2 to 3 meters long. Rubber tires can also be used to clamp seedlings for hanging culture.

(2) Cage culture: Cultivation using scallop cages. Oyster seedlings without a fixed base or oyster seedlings fixed to shells are placed in scallop cages together with shells and suspended on floating ropes. Raft culture generally releases 100,000 oyster seedlings per mu, using shells as seedling collectors, and can be suspended for about 10,000 shells per mu. Oyster seedlings are released from May and June and harvested at the end of the year, with a yield of more than 5,000 kg per mu.

2. Tidal flat farming

(1) Site selection: For tidal flat farming, the best choice is an inner bay with small waves, smooth tides, and no pollution. The bottom should be sandy muddy beach or muddy sandy beach. The tidal area should be located at the lower part of the mid-tidal area and near the low-tidal area.

(2) Seedling planting season: Generally, the most suitable time for seedling planting is from mid-March to mid-April. In terms of production, the latest time for seedling planting is mid-May.

(3) Seedling planting method:

Low tide seeding: seeding is done when the beach is dry and exposed after low tide. The beach should be leveled or built into a ridge before seeding. For low tide seeding, try to make sure that the tide starts to rise right after seeding to shorten the time when the oyster seedlings are exposed to the sun and avoid seeding during the midday sun exposure.

Water seeding: It means seeding by boat after high tide. Before seeding, the beach is divided into strips, and bamboo poles and wooden poles are inserted as marks. After high tide, oyster seedlings are scattered on the boat with a shovel. Since the distribution of oyster seedlings cannot be directly observed during water seeding, seeding is often uneven. The seeding density should be determined according to the quality of the beach and the fatness of the water. For excellent beach, about 120,000 seedlings are planted per mu, for medium-quality beach, about 100,000 seedlings, and for poor-quality beach, 60,000 to 80,000 seedlings can be planted.

3. Oyster and shrimp mixed culture

(1) Shrimp pond selection: For shrimp ponds that are mixed with oysters, the bottom material should be muddy or muddy sandy, the water depth should be more than 1.3m, and the average daily water exchange rate should be about 50%. The transparency should be controlled at 40-50cm in the early stage and 50-60cm in the middle and late stages.

(2) Site preparation: Before stocking the seedlings, the silt must be thoroughly cleared and the bottom of the pond where the oyster seedlings are to be planted must be leveled and compacted using a bulldozer or other tool to create a slightly convex shape that is slightly higher than the surrounding bottom surface. This can prevent the oyster seedlings from sinking and being buried in the silt, causing their death.

(3) Seeding: Under the premise of ensuring the normal shrimp stocking density, the appropriate amount of oyster seedlings to be sown is about 30,000 per mu. The sowing time should be chosen in early April, and the seedling size should be more than 2 cm in shell length. The sowing stress should be uniform, and avoid the low-lying areas of the ring ditch and the feeding area. The sowing area should account for 1/4 to 1/3 of the pond bottom area.

4. Stone throwing farming

The stones used as oyster seed collectors now become oyster cultivation equipment. The short-lived Crassostrea gigas can be cultivated locally at the seed collection site; the long-lived Crassostrea gigas must be moved to the cultivation site for cultivation. There are three main cultivation methods: the star-shaped method, the plum blossom method, and the determinant method:

(1) Starry sky: Stars scattered all over the sky, scattered around in a disorderly manner.

(2) Plum blossom style: Generally, 5 to 6 oyster stones form a group.

(3) Determinant: row width 0.5-1m, row spacing 0.6-1.5m. Deep water aquaculture can be done without any management after stone throwing and seedling collection until harvest.

5. Bamboo planting

The oyster seedlings are collected by planting bamboos and cultured sparsely on site. There are two ways to arrange the oyster bamboos during cultivation:

(1) Direct insertion: 150 to 179 oyster bamboos are inserted in a row with a length of 3 to 5 meters; or 100 to 120 oyster bamboos are inserted in a row with 2 to 3 gaps in the middle to facilitate water flow.

(2) Oblique insertion: 23 to 26 oyster bamboos are inserted into a pile, with a bottom width of 45 to 60 cm and a top width of 33 to 36 cm. The distance between piles is 20 to 25 cm. 5 to 6 piles form a row, with a distance of about 2.5 m between rows. 8,000 to 10,000 oyster bamboos can be inserted per mu.

6. Bridge culture

After collecting seedlings using the bridge method, the stone bars are rearranged to disperse the density for growing. Generally, 6 to 7 stone bars form a group, and the groups are connected by stone bars to form a row. The distance between groups is 50 to 60 cm, and the distance between rows is 1 to 2 meters. During the growing period, the shady and sunny sides of the stone bars should be interchanged to ensure that the oysters on both sides grow evenly.

7. Standing Stone Farming

After the seedlings are collected in the mid-tidal area using the standing stone method, as long as the seedling quantity is appropriate, they can be left to grow naturally without any management until harvest. This method is mainly used for the cultivation of Crassostrea gigas.

8. Fence culture

This method of breeding is to set up fixed racks in the inner bay at a depth of 2 to 4 meters, when the wind and waves are calm and the bait is not available. The racks are set up in the same way as the rack-type seedling collection. Oyster seedlings are mostly raised in strings on the racks with shells, cement tiles and other fixed bases in series. Each string is 1 to 1.5 meters long, with a spacing of 0.5 to 1 meter between strings. The breeding density should not be too high to prevent the bottom from being touched, so as to avoid the invasion of some benthic pests.

3. Disease prevention and control of oysters

1. Oyster disc virus disease

This disease is caused by the oyster veliger virus. In the nursery, the disease usually occurs from March to August, and it is seasonal. The shell height of the affected larvae is greater than 150μm. The disease may be transmitted from latently infected parent oysters, resulting in longitudinal infection, and the loss of nursery can reach 50%. The activity of the diseased larvae decreases, and the viscera retract into the shell. The veliger is not active normally, the epithelial cells of the veliger lose their flagella, and some cells separate and sink to the bottom of the culture container and become inactive.

Prevention and control methods: After the pathogen is identified, the diseased oysters and broodstock are destroyed and the culture facilities are completely destroyed. The disease-free broodstock population is identified and preserved.

2. Oyster herpes virus disease

This disease is caused by herpes virus. It often occurs in oysters cultured in hot water discharged from power stations. The water temperature at which the disease occurs is 28-30℃. When the water temperature drops, the disease disappears. The onset is closely related to the water temperature. The digestive glands of infected oysters are grayish-grey and sporadic deaths occur.

Prevention and control methods: After the disease is discovered, transfer the oysters to natural seawater with low temperature to prevent further infection and death.

3. Larval oyster canker

The disease is caused by Vibrio anguillarum and Vibrio alginolyticus. Because Vibrio exists in seawater, sediment, and on the surface of oysters, it is an opportunistic pathogen and can occur in all kinds of oyster seedlings cultivated in hatcheries across the country.

Prevention and control methods: (1) Keep water clean and strengthen bacterial inspection of water bodies and sediments;

(2) If diseased larvae are found, they shall be destroyed immediately;

(3) The algae fed are guaranteed to be free of Vibrio contamination;

(4) Use seawater that has been disinfected by filtration, ozone, ultraviolet light, etc.

(5) Use 50-100 grams of compound streptomycin per cubic meter of water and spray it throughout the pond.

4. Pit necrosis

The disease is caused by an unknown bacillus. When infected, oysters have punctate necrotic tissue, diffuse cell infiltration, and a large number of bacilli when dying, with pale digestive glands, open shells, and sporadic deaths.

Prevention and control methods: Separate and destroy diseased oysters in time.

5. Vibrio disease

The disease is caused by Vibrio bacteria, which primarily infect young oysters and can cause more than 50% mortality in young oysters. Infected oysters have deformed shells with large, uncalcified chitinous areas around them, and the bacteria infect deep into the ligaments, preventing the shell from growing and impairing ligament function.

Prevention and control methods: Disinfect the breeding facilities, soak the diseased oysters with 10PPM sodium hypochlorite and then rinse with clean seawater.

6. Blight

The disease is caused by the fungus Oxyphylla sphaeroides. The fungus grows in a curved pattern with a few branches, which can attack juveniles of all stages, causing mass death. Soon after the young oysters are infected, they stop growing and moving and die soon after.

Prevention and treatment methods: Filtration, ultraviolet disinfection of seawater and other methods have a certain preventive effect, but there is no effective treatment after the onset of the disease.

4. Harvesting and processing of oysters

1. Harvesting: Harvesting is done from May to June every year, when the oysters' reproductive glands are highly developed but they have not yet reproduced and the soft parts are the fattest. When harvesting, scoop up the oysters.

2. Processing: Shell the harvested oysters, remove the meat, take out the shells, wash them and dry them.

Juvenile oysters can be attached to the shell.