CATDOLL : CATDOLL: Which salinity or temperature is more suitable for clams farming?

1. Which salinity or temperature is suitable for clams farming?

Which is more suitable for aquaculture, salinity or temperature? Of course, the salinity is about 5%, and its temperature must be maintained between 20 and 35 degrees.

2. How to preserve live clams, such as refrigeration, what temperature should be set for how many days they can survive, and can they survive if they are put in water to spit out the sand and then wrapped in a nylon bag and refrigerated?

You can mix sea salt (table salt is also fine) into clean water, trying to make it slightly saltier than seawater. Then put the clams in, making sure the water is deep enough to cover the clams, and place it in a relatively cool place.

Introduction:

Flower clams (gé), a treasure among shellfish, are named for their smooth shell surface with beautiful red, brown, black and other patterns.

Clams are common shellfish in the market, widely distributed in the southern and northern seas of China. They grow quickly, have a short breeding cycle, are highly adaptable (wide temperature, wide salt, and wide distribution), and can survive long out of water. They are a good shellfish suitable for high-density artificial breeding and one of the four major farmed shellfish in China. They can be eaten and cooked.

Dietary effects:

Clam meat is delicious, nutritious, high in protein, and has a reasonable composition and ratio of amino acids; it has a low fat content, high in unsaturated fatty acids, is easily digested and absorbed by the human body, and contains various vitamins and medicinal ingredients. It contains a variety of essential trace elements for the human body, such as calcium, magnesium, iron, and zinc. It can be used as a nutritious and green food for humans and is favored by consumers. Clam meat and shellfish mollusks contain Dalta 7-cholesterol and 24-methylene cholesterol, which have the effect of lowering serum cholesterol. They have the unique effect of inhibiting cholesterol synthesis in the liver and accelerating the excretion of cholesterol, thereby reducing cholesterol in the body. Their efficacy is stronger than the commonly used cholesterol-lowering drug sitosterol. Chinese medicine believes that clam meat has the effects of nourishing yin, improving eyesight, softening hard masses, and resolving phlegm. Some shellfish also have the effect of benefiting essence and moistening internal organs. Everyone can eat it. It is especially suitable for people with high cholesterol, hyperlipidemia, and those suffering from goiter, bronchitis, stomach problems and other diseases.

To clarify the suitable storage time and storage temperature of clams in actual diet and understand the possible apoptosis mechanism of clams during their survival. Methods: The freshness and DNA damage of clams at different dehydration times at 4℃ and 25℃ were studied by K value determination and single cell gel electrophoresis. The expression changes of anti-apoptotic protein Bcl-2 in clams were studied by immunohistochemical SABC method. Results: The K value reached 64.71% after dehydration at 4℃ for 24h and 65.18% after dehydration at 25℃ for 6h. When dehydration at 4℃ for 24h and 25℃ for 6h, the cell tailing rate was 90.55% and 91.66%, the tail length was 420.61±207.62μm and 315.07±159.84μm, and the DNA content in the tail was 56.07%±22.46% and 38.19%±15.25%, respectively. At 25℃, compared with the control group, the expression of Bcl-2 in the axonal pedicle was extremely significantly decreased after 2, 4, and 6 hours of dehydration (p<0.01), and the expression of Bcl-2 in the visceral mass cells was significantly decreased after 4 and 6 hours of dehydration (p<0.05). At 4℃, compared with the control group, the expression of Bcl-2 in the visceral mass was significantly decreased after 12 and 24 hours of dehydration (p<0.05).

In fact, clams should not be stored for more than four days. So, a week is a bit too much because the clams here are basically caught in 16 hours and sold out on the second day. So, from catching to selling, it is basically completed within 4 days. My personal suggestion is that, first of all, if you are a distributor, you need to have a good relationship with the supplier, because first of all, you have to ensure that the clams you buy are the freshest, right? What if you buy clams that have been sold in the wholesale market for one or two days? ? If you want to store large quantities for a long time, you must have a cold storage to store the temperature at about 3-5 degrees. If you really don’t have it, I suggest that you must use nylon mesh bags to pack the clams, and then tie each bag of clams as tightly as possible. I mean, so tight that there is no space between the clams. Then stack them up one by one, no more than 3 bags, close together, and then press ice on the top. If there is no professional cold storage, you can use an insulated foam box instead. Tie the bags tightly so there are no gaps between the clams, then pack two bags or one bag into a box, and cover them with 10-20 cm thick ice. Cover them with a lid or transparent film. I have only stored 200-300 kg of clams, and I have never tried large quantities. I suggest you try it first to see the effect.

3. How to raise clams correctly

Understand its living habits

Clam farming:

Reproduction

Clams are hermaphrodites and generally reach sexual maturity in two years. The gonads of sexually mature clams are distributed around the visceral mass and extend to the base of the foot. The female gonads are milky white, while the male gonads are light orange (or creamy yellow). The eggs are spherical, with a diameter of about 70-90 microns, and there is a layer of gelatinous egg membrane outside the eggs. The sperm is narrow cocoon-shaped and about 3 microns long.

The breeding season of clams is in early summer, which varies with species and regions. The spawning period in Liaoning, Shandong and other places is from July to August, in Jiangsu, Zhejiang and Fujian from June to July, and in Guangdong and Guangxi from May to July. The surface temperature of seawater during the spawning period of clams is about 27-29℃. The suitable water temperature for the embryonic development of clams is 24.9-31.4℃, preferably 26-28℃, the suitable seawater specific gravity is 1.010-1.025, preferably 1.015-1.025, the suitable temperature for larval growth and metamorphosis is 24.9-31.0℃, and the suitable specific gravity range is similar to that of embryonic development; when the bait is fresh, abundant and of good quality, the larvae are large and metamorphosis is early. The suitable bottom for the survival of clam seedlings requires a sand content of more than 75% (all sand is best); the seedlings are highly adaptable to low-density seawater, and can still survive and grow when the seawater density drops to 1.003-1.005 in a short period of time. The growth rate of seedlings in natural sea areas is faster than that of artificial seedlings.

Growth patterns of clams

The most suitable seawater temperature for the growth of clams is about 15-30℃. They start to grow when the water temperature reaches above 11℃ in spring, and stop growing when the water temperature drops below 10℃ in winter. The fastest growing period for clams in southern Zhejiang is from April to June and from September to November, and the growth rate is extremely slow from December to February of the following year. The growth rate of clams varies significantly with the size of the individual. The shell length and weight growth rate of smaller clams are much faster than that of large clams. The ideal water level for clams in shrimp ponds is to control the water depth on the beach to 30-50 cm. In addition, the abundance of bait in the pond and the quality of the bottom are important factors affecting the growth rate of clams. During the breeding period, clams should be moved as little as possible unless they must be moved due to high density or other reasons. Once moved, the growth of clams will be greatly affected.

Cultivation of suitable seedlings of Meretrix meretrix

Suitable seedlings for clams are to cultivate 0.5-1.0 mm clam seedlings into 50-70 pieces/500g of suitable seedlings in stages. In the first stage, the 0.5-1.0 mm seedlings are cultivated into 0.8-1.5 cm seedlings, which are screened and evenly dispersed to cultivate into suitable medium seedlings of about 3 cm. The water depth on the beach of the cultivation pond is 15-30 cm to facilitate the rapid reproduction of benthic diatoms. The water level is appropriately raised as the water temperature rises, and the specific gravity is maintained at 1.010-1.017. The pond water is preferably dark brown with a slight diatom.

Clam culture technology

1. Beach clam farming

Beach clam farming has a long history in China. The clams farmed on natural beaches are brighter in color than those farmed in ponds, but they are not as plump as those farmed in ponds.

In addition, the frequent occurrence of red tides along the coast of China often causes large-scale deaths of clams, which directly affects the development of beach clam farming.

1. Selection of breeding sites: For breeding clams on natural beaches, you should choose a beach with small tides (large tides will cause a large loss of clams), a large continuous beach area, fine sand, and a seawater salinity between 5% and 30%.

2. After the beach for seedlings is selected, fences are set up around the beach to prevent clams from migrating and predators from invading. The fence should be about 1.5 meters above the beach and buried more than 0.5 meters into the sand layer. In the aquaculture area with slightly larger tides in the sea area, it is best to arrange two levels of fences. It is appropriate to release 200-250 kg of clam seedlings with a specification of 120-200 pieces/500 grams per mu. The specific amount of release should be reasonably adjusted according to the size of the seedlings. Unreasonable seedling stocking density will directly affect the growth of clams. The increase in the weight of clams is not only affected by the growth time and stocking density, but also by the combined influence of these two factors. Therefore, the stocking density should be adjusted with the growth time. In addition, it should be noted that the broken and dead clams should be removed in time when the seedlings are released, and the clams that cannot be buried in the sand in time should be removed even if they are not dead, so as not to affect the healthy clam seedlings.

3. Cultivation and management

① Take samples regularly and measure and observe their growth every ten days. In particular, the strong tides brought by typhoons will cause the local density of clams to be too high, so they should be evacuated and stocked in time. In addition, we must pay close attention to the changes in the seawater environment, especially when encountering disasters that cannot be resisted by human power, such as red tides. If a large number of clams are found to have died, they should be removed in time; if the environment in the sea area continues to deteriorate, clams should be caught in time to reduce losses if necessary.

② To eliminate pests, the seine net must be checked every day. If it is found to be tilted or damaged, it must be repaired in time. The net must be carefully checked for invading pests such as river crabs. Once found, they must be removed in time.

(II) Pond clam farming Clam pond farming has developed rapidly in recent years. Because the water quality in shrimp ponds is rich and there are a lot of residual baits, it is less affected by changes in climate, tides and sea conditions. The ecological environment for the growth of clams is excellent. Therefore, its growth rate is much faster than that of tidal flat farming, its fatness is high and its efficiency is good, and it has already shown a trend of catching up.

1. Preparation before stocking Before stocking, the pond should be fully disinfected and sterilized, and quicklime (100kg/mu) and tea cake (100kg/mu: calculated by water area) should be used for double disinfection and cleaning. After the pond is disinfected, choose a beach with a harder bottom to level and spread sand (it is best to choose a beach close to the ring ditch and make a ridge with a width of 4-5 meters and a height of 25-30 cm). The sand-spreading area accounts for about 1/3-1/4 of the total pond area, and should be adjusted according to the specific pond water body. If the breeding area is too large, it will affect the growth rate of clams, and if the area is too small, the breeding capacity of the pond cannot be fully utilized.

2. Stocking seedlings should be done on cloudy days, at dawn or dusk. This is especially important when the climate is hot and the seedlings are small. The seedlings should be evenly spread and not piled up. The stocking rate of seedlings with a size of 50-60 pieces/500 grams per mu should be around 500-700 kilograms. If the area for clams is less than 1/4 of the total area of ​​the shrimp pond, the stocking rate can be increased as appropriate, but it should not exceed 1,000 kilograms. If the area for clams is larger than 1/3 of the pond area, the stocking rate should be reduced as appropriate. The stocking rate of small seedlings with a size of 300-500 pieces/500g should not exceed 200 kilograms per mu.

3. Cultivation and management

① Water temperature and water quality monitoring: Water temperature and water quality monitoring should be done well, water temperature should be measured every morning (6:00) and noon (14:00), and water color should be observed. Water should be replaced based on water quality on a daily basis, pH value in the pool should be controlled between 7-8, dissolved oxygen should be above 4mg/l, water color should be mainly maintained in an ideal yellow-green color, and transparency should be controlled between 20-40CM.

② Regular sampling and measurement: Take samples every half a month to measure and observe their growth. If the density is too high or clams are found in piles in some places, they should be evacuated and released in time. As long as the environment is suitable, clams rarely migrate.

③Bait management is mainly to cultivate the biomass of bait in the pond. In early spring, fresh small fish and shrimp paste is used to fertilize the water and increase the amount of organic debris in the pond; compound fertilizer and organic fertilizer are used to fertilize the water on sunny days in summer and autumn; soybean milk is used to be sprinkled throughout the pond for feeding in late autumn and winter.

④Disease prevention and control measures: Use quicklime (10kg/mu) or chlorine dioxide (0.125kg/mu) and other drugs to disinfect water bodies and prevent diseases every other month.

⑤ Elimination of pests The nets used to block pests and prevent them from escaping are generally 1.2 meters high and buried 0.2 meters into the beach surface. However, they must be checked regularly and repaired in time if they are found to be overturned or damaged. After each drainage, the beach surface should be carefully checked for the presence of pests such as blue crabs. Once found, the pests should be removed in time.

⑥ Prevent the growth of Enteromorpha on the beach. The Zhejiang coast is basically a regular half-day tide. The water in the pond for clams is changed every half a month. When changing the water, let the beach dry for 1-2 days. The silt that washes into the site should be cleaned immediately to effectively prevent the growth of Enteromorpha on the beach. Especially in spring and autumn, floating moss is very easy to grow on the clams, so it should be removed manually or with drugs.

Cause of death

① One of the reasons for the death of clams is that the density is too high and the individuals are thin after reproduction. According to tests, the soft parts of clams are plump before the peak reproduction period, with a fatness of 15%-25%, but they become thin immediately after the peak reproduction period, with the fatness dropping to 4%-12%. Such clams are very likely to die when the environmental factors suddenly change.

② High temperature, heavy rain and low pressure are important meteorological factors that cause the death of clams. Thunderstorms after exposure to the scorching sun are extremely harmful to clams. Continuous heavy rain will cause the specific gravity of seawater at the mouth of rivers to drop rapidly to below 1.003.

③ The clams that die during the high temperature period rot and infect each other, causing the death of a large number of clams in the surrounding areas.

④ Parasitic diseases, pond water quality, bottom sediment pollution, excessive amount of bottom sediment sludge, etc.

Reference link: Clam_Baidu Encyclopedia