White prawn Seedling Desalination Technology

Although the factors causing the failure of Penaeus vannamei to dilute aquaculture production are numerous and intricate, follow-up analysis of its source and the improper management and operation of the shrimp in the process of desalinating the rough (referring to intermediate breeding) is one of the keys that cannot be underestimated. factor. In view of this, the author now summarizes the relevant operational technical specifications for the reduction of crude white prawn seedlings in South America and gives an overview to the industry for reference.

1 Incubation room

In order to facilitate the daily feeding and management and operation, the entire process of desalting the shrimp should be carried out in the cultivation room (normative or standard for the cultivation room). The standard coarse pool is a cement tank with a specification of 4.3m and a depth of 1.2m.

2 Preparations before the seedlings

2.1 Selection of shrimp seedlings, determination of water quality, virus detection This is a prerequisite to ensure the success of desalination of shrimp seedlings. Therefore, the technical staff responsible for this work must be careful and meticulous, and should be randomly selected from the shrimp ponds to be purchased. A number of tail shrimps were carefully removed and visually inspected for quality. The quality of the shrimp should be: the seedlings are not deformed, the appendages are intact, the body surface is smooth, the specifications are neat, the edges of the cephalothorax are not rolled up, the eyes are clear and symmetrical, the tail fan is open, the muscles are full, and the swimming is lively. The stimuli response is very agile, and there are top water swimming (water repellency) and wall-fouling behavior. In addition, the specific gravity of the pool water should also be recorded (normally, the specific gravity of pond water at the time of emergence is about 1.015, that is, the salinity is about 20 ‰), pH value, and ammonia nitrogen. For the sake of prudence, a PCR virus test should also be performed on samples of shrimp that are about to go out of stock to determine if they carry the Taura virus.

2.2 Thoroughly wash and disinfect the scale pool and all necessary tools for use (the method and requirements are the same as for the shrimp culture tank). In addition, all equipment for the three major systems of power supply, water supply, and gas supply (oxygenation) should be carefully inspected to ensure their normal operation during the period when shrimp seedlings are diluted.

2.3 In the morning on the day of seedling, the seawater and fresh water shall be poured into the standard coarse pool, the water depth is 0.6 meters, the specific gravity of the pool water is adjusted (about 1.015), and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) is added at a concentration of 3 to 510, Micro-aerobic, strive to make the standard coarse pool water quality and nursery pool water quality close to the same.

2.4 The Artemia larvae are cultivated one day in advance to ensure that there are enough Artemia larvae for their feeding after the shrimps are placed in the standard coarse pool.

3 shrimp under the pool

It is worth to remind that the process of drainage and seedling collection in the shrimp and nursery field should be performed at noon or in the afternoon (with the exception of distant distances), and the original nursery water should be used to bag (seedlings) so that the shrimp can reduce stress. The reason for the reaction was that the shrimp shells were mostly carried out in the middle of the night. The larvae of the larvae had a softer body and a relatively weaker body, which required a certain amount of time to recover. If drip collection, bagging (miao), transportation, etc. are performed at this time and even the morning of the day, these man-made drastic operations are undoubtedly many times to force the shrimp seedlings to undergo bursts of stimulation, which will directly affect the survival of the shrimp seedlings. rate. If you use fresh water in bags (seedlings), it would be even worse.

After the shrimps were shipped back, the shrimp bags were first put into the coarse pools, and then the left hand gently flipped the bags while the right hand poured water from the scoops to pour the bags evenly. Later, place a large plastic basin on the surface of the standard tank and put a little water in it. Then open the shrimp bag and slowly plunge the shrimp into the basin with water. Then use a small scoop. Rotate pot water. For a moment, slowly raise the side of the bowl and slowly inject the shrimp into the pool water. After the completion of the shrimp seedlings, the amount of oxygen should be increased in a timely manner.

Standard density: shrimps with a body length of 0.6-0.7 cm are usually given 40,000 to 50,000 tails per cubic meter of water.

4 Daily feeding and management

4.1 Feeding the feed can be done after feeding the shrimp in the lower pool for about a small amount. Practice has proved that Artemia larvae, shrimp slices (powdered), artificial compound feed, etc. are the ideal feed for desalination of shrimp seedlings. The specific dosage is, in principle, "a small amount of hard-working investment," ie, it should be based on shrimp seedling density, size, and water quality. The entire process of roughing was mainly based on shrimp slices and artificial compound feed supplemented by Artemia larvae (mainly to reduce production costs). The feeding amount of shrimp slices and artificial compound feed was 4-5 grams per 100,000 shrimps and 25-35 grams per day, and they were fed 4 times a day. The necessary time could be increased by 1 or 2 times. Specific operations: First put the prawn slices and artificial compound feed into 60 to 80 mesh nylon sieve bags (two kinds of materials can also be used separately), then put the bags in the feed bucket and add water to squeeze by hand. Dissolve all the feed in the water, and then spread it evenly. The feed should be ready for use and should not be left for too long to prevent deterioration. Artemia eggs should be soaked in a formalin solution (50-100) at a concentration of 10 for 10 minutes before being placed in a hatchery, and then rinsed with fresh water several times before hatching.

4.2 Changing Water (Adjusting the proportion of pool water) Starting from the next day after the shrimp pond is in the pond, add 5 centimeters of freshwater every morning, so that the proportion of pool water will decrease by “1 grid” per day (commonly known by shrimp farmers in Hainan Province), meaning seawater One scale on the hydrometer is 1.015 → (decrease) 1.014 → (decrease) 1.013. After 6 days, that is, from the second day after the pool water level is increased to 90 centimeters, the pool water is drained 10 centimeters in the morning, then freshwater is added to 5 centimeters, and 5 centimeters of fresh water is added in the afternoon. The pool water level is still maintained at 90 centimeters. The proportion can still be reduced by "one cell" every day. When the specific gravity of the pool water drops to 1.006 to 1.005, it means that the pool water is drained 15 centimeters every morning for the first 4 to 5 days from the 10th or 11th day after the shrimp seedlings coarse pool, and the pool water is discharged every morning for 4 to 5 days. 20 centimeters, while adding fresh water, 50% of the amount of water should be injected on the same day of the morning and afternoon, and the pool water level should always be kept at 90 centimeters, so that the proportion of pool water can be reduced by “0.6 to 0.7” per day. At this time, the pool water salinity is about 0.5‰. It seems to be all light but not all light.

4.3 Water Quality Monitoring and Determination of Growth of Shrimp Seek Insist on the movement of the shrimp seedlings and the survival rate of the shrimp seedlings after each feeding for 1 to 2 hours (checked shrimp should be randomly sampled from the surface or underlying layer of the pool water). If necessary, microscopic observations should also be used to check whether there are debris or parasites on the shrimp body surface. Measured water temperature once every morning and afternoon, every 5 days to determine shrimp body length, measured pH value, dissolved oxygen, ammonia nitrogen once. Physicochemical factor requirements for pool water during desalting of shrimps: water temperature 27°C to 31°C, pH value 7.8 to 8.7, dissolved oxygen 6 mg/l, and ammonia nitrogen 0.1 mg/l or less. The survival rate of the diluted seedlings with a body length of 0.6-0.7 cm after 18 to 20 days of scientific rearing and careful management is generally above 80%, and the body length can be up to 2 cm. Farming.

5 Discussion and Analysis

5.1 The author believes that the desalination of white shrimp seedlings in South America (middle-cultivation) must have corresponding dilution time and dilution. If the desalination time is too short and the daily desalination rate is too large, the degree of stress experienced by the shrimp seedlings will increase, and eventually the survival rate of the shrimp seedlings will be affected. Therefore, the South American white prawn seedlings should not be encouraged to desalt seedlings. The reflection of the situation from the shrimp farmers is enough to prove this. Shrimp farms on behalf of the shrimp farms to dilute crude shrimp seedlings because of the desalination time is short (5 to 7 days), body length at the top of more than 1.0 centimeters, while the proportion of pool water is 1.006 ~ 1.005. This type of shrimp was put in the pond (all light) and the survival rate was very low (40%), and even the entire army was annihilated, resulting in heavy economic losses.

5.2 For the same sea area, the quality of seawater used to evaluate the dilution of seabass with useful plankton (referred to as diatoms) is: brine (its use ratio to seawater is 1:2.5 to 3 ) Seawater pumped from natural sea areas and precipitated for 24 hours, and seawater extracted from sand filter wells.

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