CATDOLL : CATDOLL: What types of oysters are farmed in my country?

What types of oysters are farmed in my country?

my country is rich in oyster resources. According to the Atlas of China's Marine Bivalves published in 2008, there are about 23 species of oysters in China. Through a joint investigation by Chinese and American scientists over the past 10 years, it was found that the oysters farmed in China are basically all oysters of the genus Crassostrea. Among them, the southern production is relatively large, including the Omi oyster and the Hong Kong giant oyster, as well as some Portuguese oysters. The northern production is mainly Omi oysters and long oysters.

How to prepare the site for oyster farming?

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. They are rich in protein zinc and are 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.

Oysters are suitable for cultivation in subtropical and tropical coastal areas. They are widely distributed in my country, from the Yalu River in the north to Hainan Island in the south. Oysters can be produced along the coast. Oysters are soft-bodied, parasitic animals with shells. Oysters produced at the junction of salt and fresh water are particularly plump. 1. Raft culture Choose sea areas with smooth currents, abundant bait, calm winds and waves, and a water depth of more than 4m as oyster raft culture sites. Near-river oysters should be selected near estuaries with low salinity; Dalian Bay oysters should be selected far from estuaries and in sea areas with high salinity; Pacific oysters and pleated oysters are between the two.

There are two main cultivation methods: ⑴ Hanging rope culture: It is suitable for oysters that use shells as a fixing base. There are two cultivation methods: one is to string the shells with oyster seedlings fixed into strings with ropes, separate them with bamboo tubes of about 10 cm in the middle, and hang them on the raft frame; the other is to clamp the shells with oyster seedlings fixed in the twisted seam of a polyethylene rope with a diameter of 3 to 3.5 cm, clamp one shell every 10 cm or so, and hang them on the floating raft.

Generally, each rope is 2-3m long. Rubber tires can also be used to clamp seedlings for hanging culture. (2) Net cage culture: Use scallop net cage culture. Put oyster seedlings without a fixed base or oyster seedlings fixed on shells together with shells into scallop net cages and hang them on floating ropes. Raft culture generally releases 100,000 oyster seedlings per 667㎡, and shells are used as seedling collectors. About 10,000 shells can be hung per 667㎡.

Oyster seedlings are stocked from May to June and harvested at the end of the year. The yield per 667 square meters can reach more than 5,000 kg. 2. Tidal flat sowing 1. Site selection: Tidal flat sowing should be selected in inner bays with small waves, smooth tides and no pollution. The bottom should be sandy muddy beach or muddy sandy beach. The tidal area should be selected in the lower part of the mid-tidal area and near the low-tidal area. 2. Seedling sowing season: Generally, mid-March to mid-April is more suitable for sowing.

In production, the latest time for seeding is mid-May. 3. Seeding methods: 1) Low tide seeding: seeding when the beach is dry and exposed after low tide. The beach should be leveled or built into a ridge-shaped base before seeding. For low tide seeding, try to grasp the tide that starts to rise after seeding to shorten the time when the oyster seedlings are exposed to the air and avoid seeding when the sun is exposed at noon. 2) Water seeding: seeding by boat after high tide.

Before seeding, the beach is divided into strips and bamboo poles and wooden poles are inserted as marks. When the tide rises, the oyster seedlings are scattered on the boat with a shovel. Since the distribution of oyster seedlings cannot be directly observed when seeding with water, it often results in uneven seeding. The seeding density should be determined according to the quality of the beach and the fatness of the water. For excellent tidal flats, about 120,000 seedlings are planted per 667 square meters, for medium ones, about 100,000 seedlings, and for poor ones, 60,000 to 80,000 seedlings can be planted.

3. Oyster and shrimp mixed culture 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 40-50cm in the early stage, and 50-60cm in the middle and late stages. 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. Seeding: Under the premise of ensuring the normal shrimp stocking density, the seeding amount of oyster seedlings should be about 30,000 per 667 square meters. The seeding time should be selected in early April, and the seedling size should be more than 2 cm in shell length. The seeding stress should be uniform, and avoid the low-lying areas of the ring ditch and the feeding area. The seeding area accounts for 1/4 to 1/3 of the pond bottom area. 4. Stone throwing culture The stones used as oyster seed collectors become oyster cultivation equipment at this time.

The pleated oysters with a shorter growth period can be grown locally in the seedling field; the Omi oysters with a longer growth period should be moved to the grow-out field for growth. There are three main methods of growing: 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 done without any management after throwing stones to collect seedlings until harvest. 5. Bamboo planting aquaculture uses the bamboo planting method to collect seedlings and sparsely culture the collected oyster seedlings on the spot. When growing, there are two ways to arrange oyster bamboo: ⑴ Straight planting: 150 to 179 oyster bamboos are straightly inserted into rows, with a row length of 3 to 5m; or 100 to 120 oyster bamboos are inserted into rows, leaving 2 to 3 gaps in the middle of the row to facilitate water flow.

⑵ 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 667 square meters. VI. Bridge-type breeding After the seedlings are collected using the bridge-type seedling collection method, the stone strips are rearranged, the density is dispersed, and the cultivation is carried out.

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 cultivation 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 culture After collecting seedlings in the mid-tidal area using the standing stone seedling collection 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. Grid culture This 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 racks is the same as the grid-type seedling collection. Oyster seedlings are mostly raised in strings on the grids with shells, cement tiles and other fixed bases in series. Each string is 1 to 1.5 meters long, and the distance between strings is 0.5 to 1 meter. 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.

IX. Management during the aquaculture period 1. Turning over the rocks (moving the rocks): This is to move the position of the oyster rocks. Turning over the rocks can prevent the oysters from being suffocated by the mud and can also stir up the floating mud, increase the nutrient salt of the bait, and promote the growth of the oysters. Generally, the rocks are turned 2 to 3 times during the aquaculture period. 2. Flood prevention: In the rainy season, attention must be paid to preventing floods from flowing in, or digging ditches to prevent floods, or moving oysters to high-salinity deep water areas for aquaculture.

3. Overwintering: The Dalian Bay oysters and Omi oysters cultured in the north generally have to go through 2 to 3 winter freezing periods. Before freezing, check once and transplant the oysters that may be threatened to deep water to ensure their safe wintering. 4. Fattening: One to two months before harvest, move the oysters to a good fattening farm for fattening to increase production. 5. Prevent human trampling: Beach-sown oysters can only filter water and feed on the beach. Once they sink into the mud, they cannot live normally and will suffocate to death.

It is strictly forbidden to trample on the beach at will. When managers go to the beach, they should walk along the ditch. 6. Clear the ditch: Check the drainage ditch regularly to see if it is unobstructed. After the tide recedes, the beach should be free of water as much as possible to prevent the death of oysters due to high water temperature, lurking enemies, and deep floating mud. 7. Pest control: There are many enemies of oysters. They should be removed when turning over the rocks. During the peak breeding period of red snails and litchi snails from July to September, diving should be carried out to catch their broodstock and egg bags.

During the season when crabs are active, strengthen management and capture predators. 8. Wind protection: Typhoons are very destructive to aquaculture facilities and can also blow up mud and sand to bury anchors and oysters. Therefore, after a typhoon, timely rescue is required, rafts should be repaired, and fallen or buried anchors should be supported. X. Prevention and Control 1. Larval bacterial ulcer disease: The pathogens are Vibrio anguillarum and Vibrio alginolyticus.

alginolyticus) etc. This disease may occur during the breeding process of various oysters. After being infected, the floating larvae sink and become fixed, or their activity is reduced, and they suddenly die in large numbers. Prevention and control methods: 1) Keep the water clean; 2) Discard the diseased larvae immediately; 3) Feed the algae without Vibrio contamination; 4) Use filtration, ozone and ultraviolet light to disinfect the water for breeding alone or in combination; 5) Spray the whole pond with 50-100g of compound streptomycin or 10g of chloramphenicol per cubic meter of water for 3-5 consecutive days.

2. Perkins disease of oysters: The pathogen is Perkinsus ma-rinus. Perkins disease is one of the most serious diseases of oysters. The disease is widely distributed geographically. It mainly attacks oysters over one year old. Oyster deaths occur in summer and early autumn (August to September), and then as the weather gets colder and the water temperature drops, the death rate decreases. The occurrence of epidemics is related to higher water temperatures (30°C) and higher salinity (30‰).

When the salinity is below 15‰ or the water temperature is below 20℃ or above 33℃, oysters will not die even if they are parasitic. Chronically infected oysters will gradually lose weight, stop growing, and the development of their gonads will also be hindered. Severely infected oysters will die with their shells open, especially when the environmental conditions are unfavorable.

Prevention and control methods: 1) Avoid using infected oysters as seed; 2) Clean the oyster beds thoroughly before the oyster larvae settle and metamorphose, completely remove old oysters, and remove any objects with live oysters attached between oyster beds. Oyster beds should not be too dense; 3) Harvest oysters as early as possible when they grow to an appropriate size to avoid the occurrence of the disease; 4) Raising oysters in low salinity (15‰) sea areas can inhibit the development of the disease.

⑵ 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 with a bulldozer or other tools to make it slightly convex and slightly higher than the surrounding bottom surface. This can prevent the oyster seedlings from sinking and being buried in the silt and dying.