Discussion on Some Problems of Artificial Seedling and Desalination Technology of Penaeus vannamei In recent years, the south aquaculture of South American white prawns has increased from south to north in China, and it has been expanded to some inland freshwater areas for aquaculture, achieving a better economy. benefit. With the continuous expansion of the aquaculture area, the supply of seedlings directly affects the development of this aquaculture species. Especially in the northern regions, the majority of South American shrimp species are from Guangdong, Fujian, and Hainan due to geographical differences. Affected by many factors such as prolonged transportation, the survival rate of culture is reduced. In order to solve this problem, farmers in the northern region urgently need local production of Penaeus vannamei seedlings. In order to solve this problem, we conducted an exploration of the artificial breeding and desalination technology of Penaeus vannamei, and achieved good results. In this paper, through the summarization of each technical link and technical point in actual production, the method of raising seedlings of P. vannamei and increasing the survival rate of larvae was discussed.
First, the source and stocking density of nauplii
At present, most nursery sites in the northern region purchase larvae for nursery. When purchasing, special attention should be paid to the source of broodstock for juvenile farms. Good nauplii are generally strong in physique without any germs, and the survival rate of young sporting plants is relatively high. Higher, and the sale of larvae during the growing period of the disease rarely occurs; In addition, transportation time should also be considered, the nearest purchase can shorten the transport time. Stocking density is generally controlled at 200,000/m3 to 300,000/m3.
Second, temperature control
Although the temperature during the breeding period of P. vannamei is very high, it is better to use a warmer nursery. Nasal juveniles generally have a water temperature of 26°C to 27°C in the south, and ice cubes are added to the packing box. Therefore, when the larvae are transported to the farms after long-distance transport, they should enter the pool at a low temperature (25°C～26°C). After one day of stabilization, the temperature can be raised, and generally there is a braided phase at this time. This method of operation relieves the adverse effects of the temperature difference during transportation and enables the larvae with weaker physiology to recover slowly and robustly; if the larvae are directly put into the pool with water temperature above 28°C, the weaker larvae will Within a few hours of death, the survival rate of nursery was reduced. The suitable water temperature for the development of various larvae is shown in the following table:
Developmental temperature
N 25°C～27°C
Z1～Z3 27°C～28°C
M1～M3 28°C～29°C
P1～P10 29°C～23°C
When the larvae develop into larvae, body length up to 0.5cm, if desalination is required, the temperature can be lowered and the salt can be reduced at this time. If desalination is not required, cooling should be started. The cooling rate is generally no more than 1°C per day. The pool temperature is basically the same as the outdoor water temperature.
Third, feed feeding
The feed types and feeding methods for artificial breeding of Penaeus vannamei were basically similar to those of Penaeus chinensis. In the northern regions, fresh live bait is still the main ingredient. When the supply of fresh live bait is insufficient, substitute bait and shrimp can be used. Feeding fresh live bait not only reduces the cost of raising seedlings, but also is an important part of raising the survival rate of nursery. Specifically feed the following table:
Developmental feeding species
Z1-Z2 is mainly composed of unicellular algae, supplemented by rotifers and yeast;
Z2 ~ Z3 rotifers are mainly supplemented with unicellular algae and yeast;
M1 ~ M2 rotifers mainly supplemented with shrimp slices, halogen children;
M2 to M3 are mainly halogen-based, supplemented with rotifers and horns
P1～P10 Cladocera dominated with halogenated and halogenated adult
Feeding times: Take a small number of times and adjust the density of the biological feed in the pool. Common rotifers and cladocerans are fed once every 2 hours, and other types are fed once every 4 hours to 6 hours. Several kinds of bait should be fed alternately. Fresh live bait treatment method: live rotifers, halogen young, soaked in potassium permanganate solution 20mg/L ~ 25mg/L concentration for 5 minutes to 10 minutes, then rinse with fresh water can be fed; fresh round Insects, Cladocera, Artemia adults are filtered with mesh bags of the corresponding mesh size to remove impurities and sewage, washed with clean water and placed in a container. Add 1% to 2% of antibiotics by weight and soak for more than half an hour. Hey.
Fourth, water treatment and change the amount of water
In the nursery where the water quality is higher than that in the sea area, the non-mottling larvae enter the pool and before Z3～M, the water body shall be disinfected regardless of water supply or water exchange. In the larval rearing stage, the water supply or water exchange shall be started in the Z2 period. The amount of water is as follows: 10% to 20% of Z2, 20% to 30% of Z3 to M1, 30% to 40% of M1 to M3, and more than 50% of P.
V. Disease Prevention
The common diseases during the nursery period are mainly bacteria, fungi, and polykeosis, and these diseases must be prevented. Before the nauplii enters the pool, 1ppm to 2ppm of compound sulfamethoxazole is applied to the pool, and then 1ppm to 2ppm oxytetracycline or compound sulfamethoxazole is applied according to the amount of water exchanged for each change of water; Should prevent the invasion of its pathogens, especially when feeding fresh live food should be strictly disinfected, once the disease can be spilled into the pool of 20ppm ~ 25ppm formaldehyde solution and heating 1 °C, 24 hours after the change of water.
6. Desalination of prawn
Although Penaeus vannamei is a broad-salted shrimp, it is sensitive to changes in salinity gradients. Through multiple observations and comparisons, the shrimp can tolerate a range of changes of up to 6 in a salinity range of over 20 ‰. The range of salinity gradients that can be tolerated in the range of 10 to 20 ‰ is 4 ‰ to 5 ‰; the range of gradients that can be tolerated below 10 ‰ is within 3 ;; especially when the seedling salinity is less than 5 ç›. The range of salinity tolerable changes from 1 to 2 inches. Therefore, the dilute treatment of prawn must not be rushed. The specific operations are as follows: According to the requirements of farmers, daily desalination 1 to 2 times, each time in the 20 or more hours of desalination 2 to 3, in the range of 10 to 20, each desalination 1 to 2; It is advisable to dilute no more than 1 inch for every 10 feet or less. By diluting this gradient, the survival rate of juvenile shrimp can reach more than 95%, and the survival rate of cultivated can be greatly improved.
First, the source and stocking density of nauplii
At present, most nursery sites in the northern region purchase larvae for nursery. When purchasing, special attention should be paid to the source of broodstock for juvenile farms. Good nauplii are generally strong in physique without any germs, and the survival rate of young sporting plants is relatively high. Higher, and the sale of larvae during the growing period of the disease rarely occurs; In addition, transportation time should also be considered, the nearest purchase can shorten the transport time. Stocking density is generally controlled at 200,000/m3 to 300,000/m3.
Second, temperature control
Although the temperature during the breeding period of P. vannamei is very high, it is better to use a warmer nursery. Nasal juveniles generally have a water temperature of 26°C to 27°C in the south, and ice cubes are added to the packing box. Therefore, when the larvae are transported to the farms after long-distance transport, they should enter the pool at a low temperature (25°C～26°C). After one day of stabilization, the temperature can be raised, and generally there is a braided phase at this time. This method of operation relieves the adverse effects of the temperature difference during transportation and enables the larvae with weaker physiology to recover slowly and robustly; if the larvae are directly put into the pool with water temperature above 28°C, the weaker larvae will Within a few hours of death, the survival rate of nursery was reduced. The suitable water temperature for the development of various larvae is shown in the following table:
Developmental temperature
N 25°C～27°C
Z1～Z3 27°C～28°C
M1～M3 28°C～29°C
P1～P10 29°C～23°C
When the larvae develop into larvae, body length up to 0.5cm, if desalination is required, the temperature can be lowered and the salt can be reduced at this time. If desalination is not required, cooling should be started. The cooling rate is generally no more than 1°C per day. The pool temperature is basically the same as the outdoor water temperature.
Third, feed feeding
The feed types and feeding methods for artificial breeding of Penaeus vannamei were basically similar to those of Penaeus chinensis. In the northern regions, fresh live bait is still the main ingredient. When the supply of fresh live bait is insufficient, substitute bait and shrimp can be used. Feeding fresh live bait not only reduces the cost of raising seedlings, but also is an important part of raising the survival rate of nursery. Specifically feed the following table:
Developmental feeding species
Z1-Z2 is mainly composed of unicellular algae, supplemented by rotifers and yeast;
Z2 ~ Z3 rotifers are mainly supplemented with unicellular algae and yeast;
M1 ~ M2 rotifers mainly supplemented with shrimp slices, halogen children;
M2 to M3 are mainly halogen-based, supplemented with rotifers and horns
P1～P10 Cladocera dominated with halogenated and halogenated adult
Feeding times: Take a small number of times and adjust the density of the biological feed in the pool. Common rotifers and cladocerans are fed once every 2 hours, and other types are fed once every 4 hours to 6 hours. Several kinds of bait should be fed alternately. Fresh live bait treatment method: live rotifers, halogen young, soaked in potassium permanganate solution 20mg/L ~ 25mg/L concentration for 5 minutes to 10 minutes, then rinse with fresh water can be fed; fresh round Insects, Cladocera, Artemia adults are filtered with mesh bags of the corresponding mesh size to remove impurities and sewage, washed with clean water and placed in a container. Add 1% to 2% of antibiotics by weight and soak for more than half an hour. Hey.
Fourth, water treatment and change the amount of water
In the nursery where the water quality is higher than that in the sea area, the non-mottling larvae enter the pool and before Z3～M, the water body shall be disinfected regardless of water supply or water exchange. In the larval rearing stage, the water supply or water exchange shall be started in the Z2 period. The amount of water is as follows: 10% to 20% of Z2, 20% to 30% of Z3 to M1, 30% to 40% of M1 to M3, and more than 50% of P.
V. Disease Prevention
The common diseases during the nursery period are mainly bacteria, fungi, and polykeosis, and these diseases must be prevented. Before the nauplii enters the pool, 1ppm to 2ppm of compound sulfamethoxazole is applied to the pool, and then 1ppm to 2ppm oxytetracycline or compound sulfamethoxazole is applied according to the amount of water exchanged for each change of water; Should prevent the invasion of its pathogens, especially when feeding fresh live food should be strictly disinfected, once the disease can be spilled into the pool of 20ppm ~ 25ppm formaldehyde solution and heating 1 °C, 24 hours after the change of water.
6. Desalination of prawn
Although Penaeus vannamei is a broad-salted shrimp, it is sensitive to changes in salinity gradients. Through multiple observations and comparisons, the shrimp can tolerate a range of changes of up to 6 in a salinity range of over 20 ‰. The range of salinity gradients that can be tolerated in the range of 10 to 20 ‰ is 4 ‰ to 5 ‰; the range of gradients that can be tolerated below 10 ‰ is within 3 ;; especially when the seedling salinity is less than 5 ç›. The range of salinity tolerable changes from 1 to 2 inches. Therefore, the dilute treatment of prawn must not be rushed. The specific operations are as follows: According to the requirements of farmers, daily desalination 1 to 2 times, each time in the 20 or more hours of desalination 2 to 3, in the range of 10 to 20, each desalination 1 to 2; It is advisable to dilute no more than 1 inch for every 10 feet or less. By diluting this gradient, the survival rate of juvenile shrimp can reach more than 95%, and the survival rate of cultivated can be greatly improved.
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