Penaeus vannamei has become an important new breed of shrimp in the mainland. Due to its rapid growth, strong adaptability, and good quality, the shrimp can also achieve relatively high yields in freshwater aquaculture. After its introduction and promotion in Zhejiang Province in recent years, it has been widely recognized by a wide range of farmers and has expanded its scale of cultivation. The output has doubled. In view of the current boom in white shrimp culture in South America, this article summarizes the experiences and lessons learned from the implementation of the “South American White Shrimp Culture Technology Development and Demonstration and Promotion†at our station base, hoping to provide some references for the farmers.
This article systematically elaborates several key issues in the cultivation of Penaeus vannamei in freshwater ponds in terms of seed quality, water quality management, and feed quality.
1 Improper selection of Penaeus vannamei seedlings often results in significant losses
In recent years, the scope of introduction and breeding of Penaeus vannamei in mainland China has been continuously expanding, the area has been continuously increasing, and the yield has been continuously improved. However, the disease epidemic is not optimistic. Nearly 70% of shrimp culture ponds have disease in different degrees. Many diseases of P. vannamei are inherent, but under normal circumstances, the shrimp carrying the virus do not have any abnormal symptoms. When the shrimp is infected with a small amount of virus, and if it has strong immunity, stable environment, or infection with a weak strain, it can be latently infected for a long time without clinical symptoms; when the virus is infected with shrimp, if the environment is not suitable or changes When the shrimps are under stress, they usually die of the disease, and then the outbreaks and deaths of the populations occur.
therefore. In the selection of shrimp seedlings, "SPF" seedlings are preferred. That is, no specific pathogens of shrimp, healthy shrimp can be determined from the following two aspects:
(1) Visual observation. Healthy seedlings have the following characteristics: regular size, body length 0.6-0.8 cm, lively and robust, complete body, no injury and deformity, no weak seedlings and dead seedlings; good vitality, flexible jumping, body level during swimming Straight, strong ability to back up water; no dirt on the body surface, body color is transparent, no redness, liver heart area is dark brown.
(2) Viral testing. The water body for cultivating the shrimp seedlings is tested to ensure that the ambient temperature of the water body is not very high, and the pH value, ammonia nitrogen and nitrosonitrogen are all in the normal range (the difference from the normal culture water is not too great), wherein pH:7. 8-8.8, ammonia nitrogen: 0.4 mg/l or less, nitrosonitrogen: 0.02 mg/l or less, do not use antibiotics during the nursery; if conditions permit, it is best to test shrimp seedlings.
In addition, under the premise of considering the cost of cultivation and survival rate, we must also pay attention to the desalination of shrimp seedlings. Suitable for freshwater and low salinity farming, the lower the salinity of the shrimp seed desalination, the better, but it must still have a certain degree of salinity, the general choice of desalinated shrimp seedlings with a salinity of 1 ‰ -3 为 is appropriate. Salinity is too low and can easily cause various diseases; too high salinity will increase production and breeding costs.
2 Water quality management is the key to the success of white shrimp culture in South America.
The deterioration of water quality is the main reason for the failure of the cultivation of white shrimp in South America. We must grasp the following “five levelsâ€.
(1) Reasonable stocking. Penaeus vannamei is a marine species, although it can be bred in fresh water after desalination, it is necessary to maintain proper salinity in the aquaculture water. Therefore, the stocking density should be reasonable. If the density is too high, it is necessary to frequently change the water, so it is difficult to maintain adequate salt, easy to cause a variety of breeding diseases; In addition, after adding water or heavy rainstorm in the pond, it should be appropriate to add some salt to maintain the pond The considerable salt in the water.
(2) Water temperature regulation. If the temperature is too high, Microcystis can overproduce excessively. On the one hand, it forms blooms. It not only competes for nutrients, consumes dissolved oxygen, but also secretes toxins, which increases water toxicity and directly harms shrimp. It will also cause some shrimps to adhere to more algae and form green pods. Plugging of cocoon will cause shrimp to suffocate; on the other hand, it absorbs heat to increase the temperature of the water and reaches 36°C. When the shrimp body is bathed in high-temperature water for a long time, the appetite diminishes and the growth slows or even stagnates. Unbalanced and unstable water quality can cause a sudden and large number of non-growth shelling of shrimp, accompanied by death. If you can add some shade plants on the water, such as scoop sand, duckweed, water hyacinth, etc., the effect is good.
(3) Physical and chemical indicators. Penaeus vannamei has strong resistance to disease, but it is very sensitive to acidity, ammonia nitrogen and so on. During the culture of white shrimp, we encountered a persistent high pH of 9.6-10.4, which could not be reduced by applying conventional drugs; the effect of changing water was not very good, not only in a short time. The internal pH value of the pool water is reduced to the normal range (8.0-9.0), and the exchange of water causes a large loss of salt, the water in the pool becomes light, the hardness is low, and the buffering effect of the carbonate balance system is lacking. Large (usually around 0.8-1 pH) makes the shrimps under stress.
In addition to paying attention to pH changes in water quality management and measurement, attention should also be paid to the monitoring of nitrous nitrogen and ammonia nitrogen. In two of the pools in our papers, the conditions in the early culture period were relatively normal, the food intake was relatively large, and the growth was rapid; however, a large number of shrimps floated before and after 50 days (5 consecutive days of rain in the previous week). The surface of the water then died one after another. Afterwards, the cause was identified mainly by continuous rainfall (Acid rain in Jiangsu and Zhejiang provinces). As a result, the concentration of nitrosonitrogen in the water body rose sharply to 2 ppm or more, which exceeded the tolerance range of shrimp growth, resulting in stress and eventually causing death.
(4) floating head Pan Tong Guan. Penaeus vannamei had a strong ability to tolerate hypoxia. When the severely hypoxic floating head occurred in the same pond, South Pacific White still did not die when the young shrimp, Macrobrachium rosenbergii, and small trash fish had died of suffocation. However, we must not take it lightly, because the hypoxic floating head of Penaeus vannamei is not as obvious as other shrimps, and it must be doubled to increase its vigilance. Pay close attention to weather changes and turn on oxygen before bad weather occurs. In the season with frequent hot and cold changes, oxygen-depleted floating heads and “pan-tang†are most likely to occur, and especially “pan-tang†brings disastrous consequences. There are two basic conditions for the creation of a “pan-tangâ€: First, after continuous high-temperature weather, the water at the bottom of the pool has accumulated enough to cause a “pan-tang†of hazardous materials; second, there must be specific weather conditions for the “fire lineâ€. In order to trigger the "pan-tang" production, this "fire line" is the sudden appearance of cool weather after high temperatures. The convection of the upper and lower water layers of shrimp ponds caused the bottom of harmful substances to diffuse into the whole pool and triggered the “pan-tangâ€. At the turn of the summer and the autumn season, hot and cold air confront each other frequently. Sudden cold weather has a high probability of occurrence, so we must pay more attention to it.
(5) Fertilizer cultivation. The lack of effective nutrients in the water makes it difficult to shell the shrimp. Due to the thin shell of white shrimp, its structure requires more nutrients, and 30% of the inorganic salts required by the shrimp body come from feed, and the other 70% are directly absorbed through the stern. When the inorganic salt composition in the water is lacking, the shrimp body cannot take up enough calcium and phosphorus ions, which shows that the old shell is not completely separated from the shrimp body, and part of the shrimp adheres to the abdomen of the shrimp (mostly in the last section) or on the cephalothorax; Although the shelling can be smooth, the new shell cannot be hardened, and the shell is soft and weak and enters the process of chronic death. Therefore, we must adhere to regular supply of this kind of nutrient inorganic salt in the breeding process to make up for lack of water bodies.
3 feed is the material guarantee for the growth of Penaeus vannamei
Poor quality feeds often affect the healthy growth of shrimp. Feed quality affects the healthy growth of white shrimp from two aspects. On the one hand, the residual baits and feed leaching are the source of pond water pollution, which directly affects water quality, while water quality deterioration indirectly affects the physiological state and immunity of shrimp. On the other hand, feed is The main nutrient source of shrimp, whether the input feed can meet the nutritional requirements of shrimp, directly affect the physiological status and immunity of shrimp. Feeding high-quality feed with comprehensive nutrition and good physical properties can shorten the cycle of shrimp culture, eliminate the hazards of shrimp disease or reduce the hazards of shrimp disease, and achieve good economic benefits. With low-quality feeds that have unbalanced nutrients and poor water stability, protein levels that are lower than standard can affect normal growth. Excessive loss of feed will also support the continuous increase of organic pollutants in the bottom of the pool, resulting in the proliferation of harmful bacteria, causing the spread of diseases such as vitiligo virus disease, and will affect the breeding of the next season, causing great losses.
Particularly noteworthy is that the protein requirement of P. vannamei is lower than that of ordinary shrimp. Feeding a feed with a high protein content not only increases production costs, but the undigested excreta of Penaeus vannamei is discharged into water. Because of its high concentration of ammonia, which is easily decomposed, this substance will affect the growth of shrimp. Reduce the immune function of shrimp: Experiments have shown that the protein content in the diet is properly reduced. Water can be slowly reduced in the body. In limited water exchange, the shrimp grows well. Therefore, the nutrient content of the selected shrimp feed must be appropriate, generally 30% to 35%.
In summary, aquaculture is a systematic project. We must be meticulous and considerate during the whole cultivation process, and we must ensure that every aspect of the cultivation is well managed to raise good shrimp.
This article systematically elaborates several key issues in the cultivation of Penaeus vannamei in freshwater ponds in terms of seed quality, water quality management, and feed quality.
1 Improper selection of Penaeus vannamei seedlings often results in significant losses
In recent years, the scope of introduction and breeding of Penaeus vannamei in mainland China has been continuously expanding, the area has been continuously increasing, and the yield has been continuously improved. However, the disease epidemic is not optimistic. Nearly 70% of shrimp culture ponds have disease in different degrees. Many diseases of P. vannamei are inherent, but under normal circumstances, the shrimp carrying the virus do not have any abnormal symptoms. When the shrimp is infected with a small amount of virus, and if it has strong immunity, stable environment, or infection with a weak strain, it can be latently infected for a long time without clinical symptoms; when the virus is infected with shrimp, if the environment is not suitable or changes When the shrimps are under stress, they usually die of the disease, and then the outbreaks and deaths of the populations occur.
therefore. In the selection of shrimp seedlings, "SPF" seedlings are preferred. That is, no specific pathogens of shrimp, healthy shrimp can be determined from the following two aspects:
(1) Visual observation. Healthy seedlings have the following characteristics: regular size, body length 0.6-0.8 cm, lively and robust, complete body, no injury and deformity, no weak seedlings and dead seedlings; good vitality, flexible jumping, body level during swimming Straight, strong ability to back up water; no dirt on the body surface, body color is transparent, no redness, liver heart area is dark brown.
(2) Viral testing. The water body for cultivating the shrimp seedlings is tested to ensure that the ambient temperature of the water body is not very high, and the pH value, ammonia nitrogen and nitrosonitrogen are all in the normal range (the difference from the normal culture water is not too great), wherein pH:7. 8-8.8, ammonia nitrogen: 0.4 mg/l or less, nitrosonitrogen: 0.02 mg/l or less, do not use antibiotics during the nursery; if conditions permit, it is best to test shrimp seedlings.
In addition, under the premise of considering the cost of cultivation and survival rate, we must also pay attention to the desalination of shrimp seedlings. Suitable for freshwater and low salinity farming, the lower the salinity of the shrimp seed desalination, the better, but it must still have a certain degree of salinity, the general choice of desalinated shrimp seedlings with a salinity of 1 ‰ -3 为 is appropriate. Salinity is too low and can easily cause various diseases; too high salinity will increase production and breeding costs.
2 Water quality management is the key to the success of white shrimp culture in South America.
The deterioration of water quality is the main reason for the failure of the cultivation of white shrimp in South America. We must grasp the following “five levelsâ€.
(1) Reasonable stocking. Penaeus vannamei is a marine species, although it can be bred in fresh water after desalination, it is necessary to maintain proper salinity in the aquaculture water. Therefore, the stocking density should be reasonable. If the density is too high, it is necessary to frequently change the water, so it is difficult to maintain adequate salt, easy to cause a variety of breeding diseases; In addition, after adding water or heavy rainstorm in the pond, it should be appropriate to add some salt to maintain the pond The considerable salt in the water.
(2) Water temperature regulation. If the temperature is too high, Microcystis can overproduce excessively. On the one hand, it forms blooms. It not only competes for nutrients, consumes dissolved oxygen, but also secretes toxins, which increases water toxicity and directly harms shrimp. It will also cause some shrimps to adhere to more algae and form green pods. Plugging of cocoon will cause shrimp to suffocate; on the other hand, it absorbs heat to increase the temperature of the water and reaches 36°C. When the shrimp body is bathed in high-temperature water for a long time, the appetite diminishes and the growth slows or even stagnates. Unbalanced and unstable water quality can cause a sudden and large number of non-growth shelling of shrimp, accompanied by death. If you can add some shade plants on the water, such as scoop sand, duckweed, water hyacinth, etc., the effect is good.
(3) Physical and chemical indicators. Penaeus vannamei has strong resistance to disease, but it is very sensitive to acidity, ammonia nitrogen and so on. During the culture of white shrimp, we encountered a persistent high pH of 9.6-10.4, which could not be reduced by applying conventional drugs; the effect of changing water was not very good, not only in a short time. The internal pH value of the pool water is reduced to the normal range (8.0-9.0), and the exchange of water causes a large loss of salt, the water in the pool becomes light, the hardness is low, and the buffering effect of the carbonate balance system is lacking. Large (usually around 0.8-1 pH) makes the shrimps under stress.
In addition to paying attention to pH changes in water quality management and measurement, attention should also be paid to the monitoring of nitrous nitrogen and ammonia nitrogen. In two of the pools in our papers, the conditions in the early culture period were relatively normal, the food intake was relatively large, and the growth was rapid; however, a large number of shrimps floated before and after 50 days (5 consecutive days of rain in the previous week). The surface of the water then died one after another. Afterwards, the cause was identified mainly by continuous rainfall (Acid rain in Jiangsu and Zhejiang provinces). As a result, the concentration of nitrosonitrogen in the water body rose sharply to 2 ppm or more, which exceeded the tolerance range of shrimp growth, resulting in stress and eventually causing death.
(4) floating head Pan Tong Guan. Penaeus vannamei had a strong ability to tolerate hypoxia. When the severely hypoxic floating head occurred in the same pond, South Pacific White still did not die when the young shrimp, Macrobrachium rosenbergii, and small trash fish had died of suffocation. However, we must not take it lightly, because the hypoxic floating head of Penaeus vannamei is not as obvious as other shrimps, and it must be doubled to increase its vigilance. Pay close attention to weather changes and turn on oxygen before bad weather occurs. In the season with frequent hot and cold changes, oxygen-depleted floating heads and “pan-tang†are most likely to occur, and especially “pan-tang†brings disastrous consequences. There are two basic conditions for the creation of a “pan-tangâ€: First, after continuous high-temperature weather, the water at the bottom of the pool has accumulated enough to cause a “pan-tang†of hazardous materials; second, there must be specific weather conditions for the “fire lineâ€. In order to trigger the "pan-tang" production, this "fire line" is the sudden appearance of cool weather after high temperatures. The convection of the upper and lower water layers of shrimp ponds caused the bottom of harmful substances to diffuse into the whole pool and triggered the “pan-tangâ€. At the turn of the summer and the autumn season, hot and cold air confront each other frequently. Sudden cold weather has a high probability of occurrence, so we must pay more attention to it.
(5) Fertilizer cultivation. The lack of effective nutrients in the water makes it difficult to shell the shrimp. Due to the thin shell of white shrimp, its structure requires more nutrients, and 30% of the inorganic salts required by the shrimp body come from feed, and the other 70% are directly absorbed through the stern. When the inorganic salt composition in the water is lacking, the shrimp body cannot take up enough calcium and phosphorus ions, which shows that the old shell is not completely separated from the shrimp body, and part of the shrimp adheres to the abdomen of the shrimp (mostly in the last section) or on the cephalothorax; Although the shelling can be smooth, the new shell cannot be hardened, and the shell is soft and weak and enters the process of chronic death. Therefore, we must adhere to regular supply of this kind of nutrient inorganic salt in the breeding process to make up for lack of water bodies.
3 feed is the material guarantee for the growth of Penaeus vannamei
Poor quality feeds often affect the healthy growth of shrimp. Feed quality affects the healthy growth of white shrimp from two aspects. On the one hand, the residual baits and feed leaching are the source of pond water pollution, which directly affects water quality, while water quality deterioration indirectly affects the physiological state and immunity of shrimp. On the other hand, feed is The main nutrient source of shrimp, whether the input feed can meet the nutritional requirements of shrimp, directly affect the physiological status and immunity of shrimp. Feeding high-quality feed with comprehensive nutrition and good physical properties can shorten the cycle of shrimp culture, eliminate the hazards of shrimp disease or reduce the hazards of shrimp disease, and achieve good economic benefits. With low-quality feeds that have unbalanced nutrients and poor water stability, protein levels that are lower than standard can affect normal growth. Excessive loss of feed will also support the continuous increase of organic pollutants in the bottom of the pool, resulting in the proliferation of harmful bacteria, causing the spread of diseases such as vitiligo virus disease, and will affect the breeding of the next season, causing great losses.
Particularly noteworthy is that the protein requirement of P. vannamei is lower than that of ordinary shrimp. Feeding a feed with a high protein content not only increases production costs, but the undigested excreta of Penaeus vannamei is discharged into water. Because of its high concentration of ammonia, which is easily decomposed, this substance will affect the growth of shrimp. Reduce the immune function of shrimp: Experiments have shown that the protein content in the diet is properly reduced. Water can be slowly reduced in the body. In limited water exchange, the shrimp grows well. Therefore, the nutrient content of the selected shrimp feed must be appropriate, generally 30% to 35%.
In summary, aquaculture is a systematic project. We must be meticulous and considerate during the whole cultivation process, and we must ensure that every aspect of the cultivation is well managed to raise good shrimp.
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