CATDOLL : CATDOLL: Clams are a common seafood. What are the precautions for clam farming?

Clams are a common seafood. What are the precautions for clam farming?

The square clam, commonly known as the white clam, is named for its quadrilateral shell. Its shell is very thick and slightly quadrilateral. Both shells are extremely inflated. The top of the shell is convex, located in the center of the rear edge, slightly forward, and the tip is bent forward. The shell has a skin, the top is white, the juvenile is lavender, the near ventral edge is yellow-brown, and the ventral edge often has a narrow edge. The growth lines are obviously thicker, forming uneven concentric rings, the inner surface of the shell is white, the hinge part is wider, the left shell has a forked main tooth, and the right shell has two main teeth arranged in an "eight" shape; the front and rear teeth of both shells are lamellar, the left shell is single, and the first shell has bright double lamellar. The external ligament is small and light yellow. The internal ligament is large and yellow-brown. The adductor muscle mark is obvious, the anterior adductor muscle mark is slightly smaller and oval, and the posterior adductor muscle mark is slightly larger and nearly round. The outer coat mark is clear and close to the ventral edge.

Clam meat is edible, delicious and nutritious. Cultivating four-cornered clams is economical. 1. Proliferation methods. (1) Resource protection: Close the beach for care and protect the nursery; limit the amount of fishing, take turns to collect, prohibit human destruction, move and raise in a planned manner, and increase the amount of resources. Limit the fishing season and specifications, prohibit fishing during the breeding season, and the length of the fishing specification should be over 3.5 cm. Improve the substrate: Spreading the substrate on the good beach to provide a good attachment base for clams is an important way to increase the growth of four-cornered clams. During the seedling season, the beach is leveled to prevent flood impact and burial of floating mud. 2. Breeding methods. The site selection and preparation of farmland should be based on fine sand or muddy sand, flat and stable beaches, and medium and low tide areas. After site selection, it should be leveled and removed, and the entire farmland should be surrounded by a polyethylene net with a height of about 0.5 meters.

Larger farmland should be separated by nets and divided into several small areas to avoid the accumulation of four-cornered clams when moving. The stocking density should be determined according to the purpose of aquaculture and the conditions of the sea area, and the temporary stocking density can be higher. Generally, when larvae with a shell length of 2 cm are put into aquaculture, the density can be controlled at 50070 kg/mu. (3) When the beach is cleared and the tide recedes, the young clams are evenly scattered on the beach, and seeding can be carried out. They can also be transported by boat to pre-marked tidal flats and sown evenly at high tide. Cultivation management: Disaster prevention, pest prevention, and escape prevention should be carried out during the cultivation period. After heavy winds and heavy rains, check the blockage. If clams are accumulated due to rolling and waves, evacuate in time. Harmful snails, fish, crabs, birds, etc. in the aquaculture area should be collected or driven away frequently. In spring, young clams with a body length of 2 cm can grow to 3 cm after autumn. Four-cornered clams can be harvested when they are about 3 cm long.

First of all, it depends on the place you choose. Generally, you should choose a tidal flat with small waves and a small amount of fresh water. It is best to choose a place at mid-tide or low-tide. The land is relatively flat and the water quality is not polluted. Such a place is convenient for both the cultivation process and the later management. 2. After choosing a good place, the next step is to transport the seedlings. When transporting, remember not to transport them with water, but to transport them dry, because they are more resistant to dryness. However, winter and summer are still very different. In winter, they can survive for two or three weeks, but in summer, they can only survive for two or three days. Therefore, there must be a certain humidity during transportation, and the temperature must be controlled relatively low, which is conducive to transportation.

Breeding site. Clams should be cultured in low-tide tidal flats with smooth tides, flat terrain, and high sand content, or in ponds with good water quality and bottom conditions. The transportation conditions of the breeding site must be good and it should be far away from industrial pollution areas. For culture on tidal flats, the beach should be turned over and the mud and sand turned over should be leveled after being washed by the tide and exposed to the sun. In areas that are easily washed by the tide and covered by mud and sand, embankments should be built to prevent floods and prevent seedling loss. For pond culture, dams and sluices should be repaired. One month before stocking, the pond water should be drained, the bottom should be exposed to the sun, and disinfection should be done. Then, filtered seawater should be discharged for culture.

First, the water quality must be fertile, preferably containing rich plankton. Second, the water quality must be fresh and have sufficient oxygen. Note that weakly acidic water is not suitable for raising clams.

How to raise clams

When raising clams, you should pay attention to the following aspects:

Transport of clam seedlings

When the seedlings grow to commercial specifications (referring to white seedlings, medium seedlings, and large seedlings), they can be transplanted for cultivation or sold. The time for washing seedlings should also be determined by the climate and tides. The high tides are at 12 o'clock on the first and fifteenth day of the lunar calendar (midnight and noon). The time difference of high tide every day is about 50 minutes. It is usually carried out in cool weather, non-rainy days, and non-low tides. In this way, the washed seedlings are strong, and the transportation survival rate and cultivation survival rate are high. The seedling production area and the cultivation area are often not in the same area, so transplanting seedlings requires a period of transportation. Because the variegated clams have a strong ability to adapt to the environment, they can withstand hours or even days without drying up or dying. A certain amount of seawater is stored in the body cavity, which can play a regulating role after fishing, which brings certain benefits to storage and shipment, but the sorting time, packaging, transportation and other factors of shellfish will still directly affect their quality. In the process of transporting seedlings, the following issues should also be noted:

1) Short-distance transportation: Generally, it is transported by car, but it can also be transported by ship. If the transportation takes less than 24 hours, no cooling measures are required.

2) Long-distance transportation: Transportation lasts more than 24 hours and requires a refrigerated truck. The seedlings and ice packs are arranged alternately and separated by bamboo strips. The temperature is controlled at about 3°C. The transportation takes 80 to 100 hours and the survival rate is more than 95%.

3) Seedlings are usually packed in mesh bags, with each bag weighing about 30 kg. The mesh size should be such that no seedlings leak through.

4) The clam seedlings should be collected on the same day, and the seedlings should be cleaned and free of mud, sand and other debris.

5) The best time for transportation is on a north windy day, when the temperature is relatively low and the survival rate is high. In south windy weather, the seedlings are prone to death. It is best to wash the seedlings, transport them on the same day, and sow them on the same day. The time from seedling removal to sowing should not exceed 3 tides at the latest, so as to improve the survival rate of sowing seedlings.

6) During the process of washing and transporting the seedlings, try to avoid damaging the clam seedlings or breaking their shells, which may cause death, mutual infection, and affect the survival rate during transportation.

7) Whether transporting by car or ship, it must be covered to avoid death caused by sun and rain, but it must not be covered tightly to prevent suffocation.

8) Before transportation, the tide of the stocking ground must be accurately calculated to determine the departure time. If the seedlings are stocked in a low-tide area, they should be transported during high tide. Otherwise, when the seedlings are transported, the ground will not be dry and sowing will be impossible.

Intertidal zone culture of clams

(I) Selection conditions of breeding farms

The breeding farms for adult clams should be selected in the mid- and low-tide areas with relatively calm waves, smooth tides, flat terrain, more sand and less mud (sand content is 70% to 90%); the specific gravity of seawater is 1.010 to 1.025, and the most ideal specific gravity is 1.012 to 1.020; the flow rate is 40 to 100 cm/second.

(II) Preparation and seedling planting

1. Seedling planting season: The seedling planting season varies greatly depending on the size of the individual seedlings. White seedlings are generally planted in April and May; medium seedlings are mostly planted in December, and in some places, due to cold weather and other reasons, the planting is postponed to the spring of the following year; large seedlings are generally planted before egg laying.

2. Land preparation: Land preparation mainly involves building embankments with Miscanthus near the harbor and the edge of the subtidal zone to prevent the loss of clam seedlings. The embankment is 30 to 40 cm wide and about 25 cm high. Large tidal flats should also be surrounded by embankments with Miscanthus and divided into several blocks for easy management. Then pick up the stones and debris on the surface of the land, fill the depressions with sand, and level the surface of the land. If the land is soft, drainage ditches must be dug to prevent water accumulation in the land. Finally, one week before sowing the seedlings, sprinkle the land with bleaching powder (15 kg/mu) or tea seed cake (8 kg/mu) to kill harmful organisms.

3. Seedling sowing method: There are two methods of seedling sowing: dry sowing and wet sowing.

(1) Dry seeding: When the land is dry after low tide, unload the clam seedlings from the seed transport boats moored on the land. When sowing the seedlings, spread them evenly to prevent them from clumping. If the tide has risen and it is impossible to continue sowing the seedlings or if the sowing is not completed, unload the clam seedlings, immerse them in water, and wait until the next tide to sow them again.

Because white seedlings are small and light, they are easily carried away by the tide and lost, so this method is often used for sowing seedlings.

(2) Wet seeding: Wet seeding is to transport clam seedlings to the marked land by boat before the tide has receded from the pond, and then evenly spread the seedlings within the marked area. Seeding should be done at low tide or when the tide is slow to prevent the seedlings from being lost.

The wet sowing method increases the sowing time, improves the work efficiency and the survival rate of clam seedlings, but the sowing is less uniform. This method is only suitable for the sowing of medium and large seedlings.

4. Seedling density: Seedling density directly affects the growth rate and yield of clams. If the seedling density is too high, the clams will grow slowly; if the seedling density is too sparse, the cultivation area cannot be fully utilized and the yield per unit area is low. Therefore, it is necessary to master the appropriate seedling density. The seedling quantity should be determined according to factors such as the size of the clam seedlings, the height of the tidal zone and the bottom conditions (Table 19-6): If the clam seedlings are large, the survival rate is high and less seeding can be done; if the tidal zone is low, the clam seedlings have a long feeding time and grow fast, and at the same time there are more enemies and pests, the clam seedling damage rate is high, so more seeding should be done appropriately; the bottom of the pond with hard soil has good stability and can also be sown more.

In addition, the amount of water should be increased or decreased according to the amount of bait organisms in the sea area and the flow rate.

Table 19-6 Relationship between clam seedling sowing density, seedling specifications and site conditions.

3) Cultivation and management

As the saying goes, "three parts seedlings, seven parts management". Doing a good job of management during the growth period is an important measure to ensure increased yields.

1. Transplantation: The main purpose of transplantation is to transfer the breeding tide area, disperse the breeding density and promote growth.

(1) Seedlings are enlarged and transplanted sparsely: The tide zone where seedlings are sown is high. After 6 to 7 months of cultivation, the individuals are significantly enlarged and the food intake increases. The stocking density is relatively too dense. At the same time, the clams' physical fitness gradually improves and their ability to adapt to the external environment is stronger. Therefore, they should be moved to a lower tide zone for stocking and the stocking density should be appropriately reduced to accelerate the growth of clams.

(2) Transplant in different seasons to improve the survival rate of clam seedlings: Based on the good thermal insulation of the mud layer, the clam seedlings are not easily frozen to death in winter, and the sand court has a large water storage capacity and low temperature, so the clam seedlings are not easily sun-dried to death in summer. With different seasons, they can be transplanted to different sites to improve the survival rate. The method of harvesting and transplanting can be adopted.

(3) Accelerate the recovery of the clams after spawning and promote growth by transplantation: After spawning and ejaculation, the clams are weak and have poor adaptability to environmental factors, which can easily lead to death. Therefore, before the breeding season, the clams should be transplanted to a place with low tide, abundant bait, and calm water to restore their physical condition and accelerate their growth.

2. Prevent disasters and enemies: The natural disasters that seriously threaten clams are mainly floods and typhoons. In the acreages that are vulnerable to typhoons, efforts should be made to harvest or transplant them to safe areas before the typhoon season arrives; similar measures should be taken in the acreages threatened by floods; victims who are not harvested or transplanted in time must be rescued in time, the mud and sand covering the acreage surface must be cleared, and the scattered clams must be gathered to reduce losses.

The pests of clams and their control measures are as mentioned above. During the culture period, the ponds should be frequently cleaned to reduce losses.

3. Strengthen daily management: After the clam seedlings are released, it is necessary to frequently inspect the ponds to check whether the clam seedlings have been lost, the growth rate and survival rate of the clams, the damage caused by enemies, etc., so as to replenish the seedlings in time or take corresponding measures. At the same time, it is necessary to dredge the ditches, fill the pond surface, and repair the dams. Especially the parent clams that have just reproduced are weak and most of them float on the surface of the pond. If they are trampled by people, the mortality rate is even greater. Therefore, after the breeding season, management should be strengthened or transplantation should be carried out.

References:

Flower clams are also commonly known as variegated clams. They are shellfish seafood belonging to the family of Curculidae. Their scientific name is Ruditapes philippinarum. They are commonly known as flower clams (huage) in the south, xianzi (xianzi) in Liaoning, and gala (gala) in Shandong. Their Japanese name is Asari, and their English name is short-necked clam. Flower clams are widely distributed in the southern and northern seas of my country. They grow rapidly, have a short breeding cycle, are highly adaptable (wide temperature, wide salt, and wide distribution), and can survive long out of water. They are an excellent shellfish suitable for artificial high-density breeding and are one of the four major breeding shellfish in my country.

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