Crayfish culture method
I. Water Quality Management
1, fertilization
In addition to the use of basal fertilizer to fertilize water before feeding crayfish fry, the shrimp ponds should also apply certain fertilizers according to the changes in water quality to ensure the supply of zooplankton in water. Top dressing is based on decomposed organic fertilizers, and less fertilizer is used, especially ammonium bicarbonate cannot be applied. When applying topdressing, it is necessary to make less use of the fertilizer and to apply it in a diligent manner. The amount of fertilizer should not be excessive for each time to facilitate the control of water quality. Generally applied once a month, each time the amount of fertilizer per mu is about 100 kilograms, the amount of top dressing should be adjusted according to the season, weather, temperature, water and so on. Generally, in spring and autumn, due to low water temperature and slow decomposition of organic matter, the amount of fertilizer can be appropriately increased. In summer and other high-temperature seasons, the amount of fertilizer should be reduced. When the weather is fine, it can be applied more, and less rainy days. The thundery days before the thunderstorm days are not applied. When the fertilization depends on the color of the water, the general pond water is grass green, dark brown and no turbid water is good water, when the transparency is below 30 cm, no fertilizer is applied, fertilize timely when the water is more than 30 cm, if the water is dark brown or water area is gathered Yellow-green blooms should be replaced with water before fertilization.
2, adjust the water quality
In the crayfish culture process, when the temperature is low in early spring, the water level can be lowered to maintain a water depth of 30-60 cm so that the water temperature can rise quickly. Afterwards, as the temperature rises gradually, the water level can be increased gradually. In the summer hot season, keep the water depth at 1.5-2 meters. If the water level is too low during high summer temperatures, it will accelerate the development of the gonads of crayfish, causing the shrimp to become precocious, resulting in a small individual commodity shrimp. Generally during crayfish culture, when the temperature is low, fresh water should be filled every 10-15 days, and water should be added every 7-10 days in summer to keep the dissolved oxygen in the water at 5 mg/L or more.
Where conditions permit, an aerator should be installed so that the amount of dissolved oxygen that is too low in the water can be replenished promptly during periods of high temperatures, rainy days and sudden changes in the weather. Shrimp ponds should choose air compression aerators and spray aerators, the advantage is not afraid of slap and stir the water, to avoid the damage to the shrimp. The impeller type aerator and the waterwheel type aerator have the same power as the spray type aerator, and they are more likely to injure shrimps. The water depth of this kind of aerator must be kept at 1.5 meters. the above.
If crayfish are found climbing out of the water during sunny weather during the day, it is proved that the lack of oxygen should be filled with new water in a timely manner. Observe changes in water quality regularly to keep the water quality in a state of fatness, livelihood, tenderness, and coolness.
Fertilizer: refers to the appropriate concentration of water, which is beneficial to the amount of phytoplankton that shrimps digest. The general transparency is 25-35 cm, and the water color is dark brown or grass green.
Live: It means that the color and transparency of the water constantly change with the strength of the sun. This is mainly due to the fact that the dominant population of phytoplankton in the pond alternates and is full of vitality. Fishermen often say that "early clear late green", "early red and late green", "half pool red half pool green" refer to this change. If yellow and green water intertwine together like a cloud of water in the pool, it is the indigestible algae in the water. It is a sign of water quality deterioration and should be changed in time. In addition, the activity of pool water not only varies at different times of the day, but also periodically changes every 10-15 days, which means that beneficial algal populations are in a state of benign circulation that is constantly being used and growing.
Tender: refers to water and fat but not old. There are two main types of signs in the water, one is that the water is yellow or yellow-brown, and the other is water-white. The appearance of these signs is due to the deterioration of water quality caused by the large number of cyanobacteria that are not easily digested by fish and shrimp, or the aging of algal cells.
Shuang: It means that the water quality is refreshing, the water color is not very strong, and the transparency is 25-35 cm.
Second, feeding
Because of its low density in natural water bodies, crayfish can meet the growth requirements of aquatic plants, zoobenthos, and other bait, so the growth is better. However, in artificially high-density intensive culture environments such as ponds, due to the lack of natural foods, artificial diets have to be fed to meet the growth and development needs of crayfish.
1, the type of food
Crayfish are omnivorous. Except for larvae and copepods and other zooplankton, except for prawns and small juveniles, other individuals also feed on plant and animal diets such as aquatic plants (water peanuts, duckweed, and malaysian eye). Vegetables, Vallisneria, Valeriana, Hydrilla verticillata, Ceratophyllum aquaticus, Eichhornia crassipes, etc.), Terrestrial grasses (fresh young wheat seedlings, seedlings, Sudan grass, ryegrass, alfalfa, vegetables, etc.), fruits (bran, sweet potatoes) , barley, corn, rice, buckwheat, bean dregs, all kinds of cakes), artificial compound feed, snails, oysters, small fish, shrimp, cockroaches, fly maggots and bodies of various animals, meat processing plants Debris and so on.
In crayfish aquaculture production, animal and vegetative diets should be properly matched and fed in order to meet the growth needs of crayfish. At the same time, it can also save feed and reduce costs. Adding 0.1%-0.15% of shrimp chitin to the fed bait can shorten the clam shell cycle, ensure the synchronization of the population clamshell, and increase crayfish production.
2, feeding place
When feeding crayfish with bait, you can set up a food table on the shore of the pond. Generally, the mat or plastic woven bag can be fixed under the water surface, and the bait can be put into the shrimp for feeding. It is also possible not to provide a food table, but to put the bait on the shore grass or water surface, so that the shrimp climb the shore to eat. It is necessary to develop the habit of feeding in order to facilitate crayfish feeding.
3, feeding method
The number and quantity of artificial feeds should be determined according to the season, shrimp size, feeding habits, etc.
Generally, crayfish of 1-3 cm size for feeding are not fed for a long time due to their small size. They can be fed 2-3 times a day and splashed along the side when feeding. At the same time, because fertilizer and water can provide more bait, the amount of artificially fed bait does not need to be large. If juvenile shrimps are released in a stocking mode, 200-500 g of fish roe, minced snail meat, soybean milk, etc., or 100-200 g of specialized shrimp opening materials are to be distributed in each early acre. After feeding for 60 days in spring and autumn and 40-50 days in summer, the individual crayfish grows and can be fed by prawn.
For juveniles with a specification of 250 animals/kg or more, feeds can be fed twice a day, and high-temperature growth seasons can be fed 3 times. When the water temperature is below 13°C, feeding is stopped. Generally, every day, every day, 100-150 kilograms of aquatic plants are planted in each acre, and feeds on animal and vegetative foods that are eaten by crayfish are kept at the same time, and the protein content of the feed is kept at about 25%. The daily feed amount is based on 2%-6% of the total pond shrimp, and it is increased or decreased according to the season, weather, water quality, physiological conditions of the shrimp, and crayfish feeding conditions. When the temperature is high, it grows rapidly, feeds vigorously and feeds in large amounts; when the temperature is low, it grows slowly, the food intake decreases, and the feeding amount is small. The suitable water temperature from June to September is the growth period of crayfish, which is usually fed 2-3 times a day. The time is from 9 to 10 am and the evening or night, and the daily feeding amount is 5%-8% of the shrimp body weight. The rest of the season is fed once a day, in the evening, or on the morning of the next day according to feeding conditions. The daily dose is 1%-3% of body weight. Feeding of bait should be paid attention to when the weather is fine, high temperature, hot and humid, continuous rainy days, or water quality is too concentrated, less investment; a large number of shrimp when the clam shell is less cast, after the clam shell and more cast.
When feeding bait, it is necessary to properly match animal and animal diets according to specific conditions. The proportion of general animal foods is 35%-40%, and that of plant foods is 60%-65%. Among plant foods, grass and fruits account for half of the total.
When feeding, the feeding emphasis of plant foods can also be determined based on the growth of grasses and cereals. For example, when grass grows vigorously in summer and the yield is high, it can be properly cast; if grasses are reduced in spring and autumn, fruits and bait can be cast more.
Third, daily management
The day-to-day management of Shrimp Pond is focused on patrol ponds. The focus of the patrol pond is to observe the activities of the shrimp, the changes in the water quality and the weather conditions.
If the crawfish are resting during the day and they are active at night, feeding is normal, indicating that the shrimp is healthy and the pond environment is also good. If the shrimp comes out during the day, check for disease. If the shrimp body is free from disease, and the food intake suddenly decreases, it will surface in large amounts during the day, indicating that the water body is deprived of oxygen and it is necessary to change the water or increase oxygen in time.
When looking at the water, in addition to the timely adjustment of the water quality changes in the control of the situation, it should also promptly repair the broken bank, timely recovery of uneaten food.
When visiting the patrol pond, we must also do a good job of preventing theft, antagonizing the enemy (frogs, rats, snakes) and other work.
In addition, the growth of crayfish is also examined. In the pond culture of shrimp, check the growth condition every 15 days after July and check the body length, body weight, and body surface color. The inspection can be randomly sampled. To avoid damage to the shrimp during the inspection, do not drain the water for inspection except for major illnesses. Catching by cages or boxes can be used to capture, and do not put many shrimp together for weighing. cause some damages.
Fourth, fishing
Due to the rapid growth of crayfish, commercial specifications can be reached within 3-4 months. When crawfish individuals become red in color, hardened crustaceans, and weighing over 20-30 g, they can be harvested and marketed. Crayfish are caught for a long time and can be harvested throughout the year, and can be harvested in a variety of ways from March to November. From December to February, due to the relatively cold weather, crayfish enter the cave for winter and can be trapped by artificial holes. However, winter crayfish either do not meet product specifications or are intended to be used as broodstock for the following year. They are often wasted after being caught and are therefore not captured.
1, mesh fishing
In the evening, the mesh is placed flat in the bottom of the pool, and the bait that the crayfish likes to eat is sprinkled in the middle of the mesh to induce the crawfish into the mesh. After pulling up the four corners of the mesh, the shrimp can be removed.
2, pull net fishing
That is, using a fishing net to catch shrimp like a fish.
3, cage fishing net
There are specialized fishing net manufacturers to produce cages for crayfish harvesting. Each cage is 10-30 meters long, about 30 centimeters wide and high, and every 40-50 centimeters has a 30 centimeter-long and 30 centimeter frame-shaped support made of iron wire or bamboo sheet. Between the formation of a grid, each grid with a barbed bar on both sides, the cage is covered with a shielding net above, the two sides of the cage are circular respectively, and the ground cage net has a net connection. Every morning or afternoon, put the cage on the edge of the shrimp pond, and put the fish with thick smell, chicken intestine and other things as bait. In the evening, when the crayfish came out for food, they smelled of stench and thought about it. Because there was a net blocking above the cage, they couldn't climb up and they looked around to find their way into the cage. The caged shrimp slides deep into the cage and becomes shrimp in the cage. This fishing method is suitable for the fishing of wild crayfish and deep crayfish fishing.
4, hand dip net fishing
The square of the shrimp is squared on the net and there is a funnel with a barbed taper along the edge of the shrimp pond or the thickets of water. The rods are constantly used to catch the shrimp. The shrimp enters the square dip net, and the net is picked up. This fishing method is suitable for use in crayfish dense areas.
5, dry pool capture
After draining the pond's water, crawfish is presented at the bottom of the pond. The shrimp can be caught by manual picking.
In addition, there are fishing methods such as the use of nets and running water.
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