(1) Prepare for cultivation
3.1 Shrimp pond dredging and disinfection
For earthen ponds that have been farmed for many years, the dams are eroded by rainwater and storm waves all year round. Usually, a layer of sludge consisting of residual baits, bio-carcasses, excrement, and clay particles is deposited at the bottom of the pond. During the cultivation period, as the water temperature rises, the organic matter in the sludge becomes the substrate for the breeding and propagation of pathogenic organisms. The rapid decomposition of organic matter consumes a large amount of dissolved oxygen in the bottom water, and produces a variety of substances that are toxic to the cultured shrimp, affecting the shrimp. Normal growth, severe shrimp can directly cause death.
Ponds are places where shrimps inhabit and live. At the same time, they are places where various pathogenic organisms are hidden and propagated. The strictness of disinfection of ponds prior to seedlings has a direct impact on the growth and health of stocked shrimps in the future. Therefore, thorough dredging and disinfection are necessary measures to prevent diseases and reduce the outbreak of epidemics. After dredging, applying 80 to 100 kg of quick lime per acre and exposing the bottom of the pool for 4 to 5 days will not only kill pathogenic organisms, but also neutralize the acidity of the sediment, increase the decomposition of organic matter, and improve the soil at the bottom of the pond. structure.
Sand ponds or high pools where the bottom of the pond is sanded should be drained and exposed for a few days. A layer of black cracked clay should be deposited on the surface of the pool's central dirt collection area. At that time, use human power to shovel it away. Then use clean seawater as the water source, flush the bottom sand with a water pump or water gun, and elute the dirt deposited between the sand particles. The last exposure to shrimp ponds, if conditions permit, the best sun bath time is 10 to 15 days.
Shrimp pond disinfection is usually carried out 15 days before seedlings. It is advisable to fill the shrimp pond with water just enough to submerge the entire pool bottom. Apply 50 ppm of bleaching powder or other chlorine-containing disinfectant to kill the pathogenic organisms that remain in the bottom of the pond and include crustaceans. Pests inside. On the third day after disinfection, the filtered seawater is refilled to 1.2 meters, and 0.3-0.4 ppm of bromochloroheine or other appropriate chlorine-containing disinfectant is used to disinfect the whole water body.
3.2 Basic food biological culture
The disinfected pool water will become more clear. After standing for 3 to 4 days, the efficacy of the disinfecting drugs will gradually disappear. After the pool is slightly yellow-green, special fertilizers for culturing unicellular algae or quick-acting biological organic fertilizers can be used to feed bait. biological. The basic bait culture before shrimp stocking is a very important part in the cultivation of shrimp, and the basic food organisms have good and poor biological culture, directly affecting the growth rate and survival rate of stocked shrimp. Basic food organisms usually refer to planktonic unicellular algae, bottom algae, rotifers, copepods, and some small benthic animals. For shrimp seedlings, the biological bait has good palatability and high nutritional value, which is unmatched by artificial baits. If shrimps are well-cultivated at the beginning of their stocking and the food organisms in the pond are abundant, the shrimps will grow quickly and have a high survival rate, and individuals will grow evenly; otherwise, the opposite will happen.
Low-end shrimp ponds are usually earthy ponds. In addition, the water quality in the harbor is relatively high, so it is easy to cultivate a higher-quality pond. The amount of fertilizer should be increased or decreased in accordance with local water quality, soil fertility, and the degree of pooling. High-level ponds have relatively clear aquaculture water sources, low levels of planktonic biomass, and high-level pools around the slope protection and sedimentation at the bottom of the pool, making the contents of various nutrients required for algae growth in water lower. Therefore, it is more difficult for the high-level ponds to be preliminarily fed before the seedlings to be cultivated than the ordinary soil ponds, and the time required is relatively long. The cultivation of basic food organisms before stocking is a key and difficult point in the production of shrimp culture in high-level ponds. According to the characteristics of high water source water quality and structure of shrimp ponds, when fertilizing the food organisms, some inorganic fertilizers or bio-organic fertilizers with comprehensive fertilizer and rapid fertilizer efficiency should be selected.
Fertilization should follow the principle of a small number of times, generally the first fertilization amount per acre of water is 1.5 ~ 2 kg, 2 ~ 3 days and then add according to the shade of water and then add as appropriate, until the shrimp pool water color appears yellow-green, transparency 40-50 When you are in centimeters, you can plant seedling The applied fertilizer shall be fully soaked and dissolved and then sprinkled in the whole pool. It shall not be sprinkled dry to prevent sedimentation to the bottom of the pool and be adsorbed by the sediment to reduce the fertilizer effect. Fertilization is generally conducted in the morning on a sunny day. It should be avoided as much as possible to make a large amount of fertilizer, resulting in a long and uncontrollable algae, and even a large number of deaths of algae, resulting in the ups and downs of the water color.
3.3 Selection of shrimp
The stocking of a healthy, disease-free shrimp seedling is a prerequisite for successful breeding. The criteria for selection are the following:
1 big quality, neat specifications. The total length of Penaeus monodon shrimp should reach 1.1-1.2 cm. The total length of shrimps of Penaeus vannamei, Japanese shrimp, and Japanese shrimp should reach 0.8-0.9 cm.
2 good vigor, quick response, strong ability to reverse water;
3 normal body color, full gastrointestinal food stuffing, body surface cleanliness, no attachments;
4 Should try to buy and feed the relatively young shrimp Artemia larvae, aquaculture production practice has shown that feeding Artemia shrimp larvae more shrimp usually have good constitution, metamorphosis development on time, fast growth, high survival rate.
5 does not contain virus particles or inclusion bodies. Two to three days before planting, it is advisable to sample the shrimp to be purchased and send it to the relevant department to check whether it has a virus.
4.1 Determination of stocking density
The stocking densities of shrimps determine the yield and quality of cultured shrimp, and even the success or failure of raising shrimp. Reasonable stocking densities should be based on comprehensive consideration of shrimp pond area, water depth, aeration facility, source water quality, water change conditions, whether there is a central sewerage facility, technical management level, and shrimp harvest specifications. The semi-intensive shrimp ponds with depths of 1.2 to 1.5 meters have poor basic conditions and are not equipped with aerators. The stocking densities of Penaeus monodon are 1.0 to 12,000 tail/mu, and the South American white prawns are 20 000/mu. If the conditions are good, the water depth is about 1.5 meters, and every 2 to 3 mu of water surface is equipped with an aerator, the stocking density can be appropriately increased to 2.5 to 30 thousand tails/mu, and the white shrimp can be 3.5 to 45,000 tail/mu. Such as the shrimp pond is in good condition, the water source is sufficient, there are matching water lifting equipment, and an aerator can be used to set intensive culture for each mu of water. The stocking density of prawn can be increased to 5.0-60,000 tails/mu, South America White. The shrimp stocking density can be increased to 70-85 thousand tails/mu. The high-level pond covers an area of ​​5-10 mu and has a water depth of 1.5-2.0 meters. It is equipped with an aerator per acre and has a central drainage system. The conditions for changing the water are good, and the stocking density of giant prawn is 60-80,000 tail/mu. White shrimp, 10-12 thousand/mu.
The increase in aquaculture production mainly depends on raising the survival rate of the culture and increasing the individual weight of the shrimp, instead of relying solely on the increase in stocking density. If operators are pursuing high yield without restriction, blindly increasing the stocking density and exceeding the maximum capacity of shrimp ponds, it will destroy the balance of ecological environment in shrimp ponds, increase the difficulty of water quality control, and increase the risk of shrimp aquaculture.
4.2 Shrimp stocking and precautions
The stocking of shrimp seedlings usually refers to the removal of shrimp seedlings with a total length of 1 to 1.2 cm from an indoor nursery pond to a rearing pool. In order to ensure good results in growing and producing, in addition to requiring that the quantity and quality of shrimps should fully comply with the requirements for grow-out production, shrimps are small and fragile and sensitive to changes in environmental conditions. Seed stocking methods.
The shrimp seedlings are moved from the indoor nursery ponds to the rearing pools. The water conditions, water temperature, salinity, water quality, type and quantity of the feeds are all changed considerably. In order to allow the shrimp seedlings to quickly adapt to the environment of the rearing ponds, To increase the effect of releasing seedlings, several precautions should be handled when releasing seedlings:
1 The natural water temperature should be above 22°C to put the seedlings. Although P. vannamei and P. japonicus are more resistant to cold, it is recommended that the temperature for releasing seedlings be higher, which will help improve the survival rate of shrimp seedlings. The climate in Hainan Province is warm. After mid-February each year, if it is not affected by the cold wave in the short term, the natural water temperature in the north central region can rise above 22°C. At this time, the breeding of early-breeding aquaculture can begin.
2 The salinity of nursery ponds and grow-out ponds cannot be too different. The salinity at the nursery is usually above 25 and stable. The salinity of the rearing ponds tends to vary greatly. For example, the shrimp ponds in the bays and estuaries have low salinity during the rainy season. Therefore, the salinity of the cultivating pool should be determined before stocking. If the salinity of the nursery and the culturing pond differ by more than 5, the necessary desalination of the larvae must be carried out.
3 Try to choose the weather in sunny weather. The time for planting seedlings should be determined according to different seasons. Generally, the temperature in early spring is low, and the seedlings should be planted at noon or afternoon. In summer and autumn, the temperature is higher, and it is better to choose to plant seedlings in the morning or in the evening.
4 A shrimp pond, the best time to put enough seedlings, and shrimp from the same seedling field, try to avoid multiple seedlings, resulting in different size shrimp specifications.
5 When purchasing seedlings, the breeding nursery with good reputation and stable yield should be selected. The quantity and quality of shrimp seedlings are more assured, which is conducive to planning production and feeding management.
6 The seedlings should be planted in deep water on the sheltered side of the shrimp pond, and not in the rough winds or in shallow waters to avoid frail shrimps being killed by the wind blown to the beach on the shore.
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