Analysis of the Causes and Treatment Methods of Penaeus vannamei (Whiteleg Shrimp) Pond-Wandering
A Brief Analysis and Treatment of the Penaeus vannamei (Whiteleg Shrimp) Pond-Wandering Phenomenon
□Text/Yu Xunhua, Zhejiang Yuehai Feed Co., Ltd.
Shrimp pond-wandering refers to a phenomenon in which shrimp exhibit abnormal activities such as slow swimming, sluggish swimming, or group swimming at the water surface, and it is a difficult problem in aquaculture. Because pond-wandering is often accompanied by shrimp mortality, many farmers treat it as a disease. Various medications have been used, but with little effect. The author's analysis of several main causes of the shrimp pond-wandering phenomenon under current environmental conditions and the countermeasures are as follows, for the reference of fellow farmers.
I. Pond-wandering caused by environmental changes
Analysis and diagnosis: After high temperatures, low pressure, strong winds, heavy rain, or typhoons, because the shrimp pond is too shallow, the polluted pond bottom is easily stirred up and made turbid by continuous strong winds and heavy rain. Changes in physicochemical factors in the shrimp pond water environment or excessive levels of toxic factors cause large numbers of beneficial algae to die off, and the pond water suddenly becomes clear or the plankton community composition in the shrimp pond changes (i.e., "algae crash"), leading to deterioration of water quality.
In practice it has also been found that if cloudy and rainy weather lasts for more than 5-7 days, after it clears up the fierce sunlight causes the water to suddenly become dense with algae, and this situation can also cause stress-induced pond-wandering in shrimp.
In ponds where pond-wandering occurs, pathogenic bacterial strains concentrate at the pond bottom and are extremely easily activated and multiplied. At the same time, the shrimp's constitution is weak, providing an opportunity for pathogens to invade, and making disease highly likely to be induced.
Solutions:
1. When weather changes occur, inject new water to raise the water level of the shrimp pond.
2. Before sharp weather changes, splash organic acids or EDTA over the entire pond to degrade toxic components such as heavy metals, increase the permeability of the water body, and create a comfortable environment for the shrimp. Then splash anti-stress preparations, such as glucose + table salt or vitamin C + vitamin E, to enhance the shrimp's anti-stress capacity. If continuous rainfall lasts too long, quicklime can be splashed 1-2 times during the period, applied at 10-12 kg per mu/m.
3. When algae phase changes occur, splash sodium humate or organic acids, and the next day splash microbial preparations over the entire pond, such as compound Bacillus, photosynthetic bacteria, or EM bacteria. If the water body is clear to the bottom, a multi-element biological fertilizer can be used to cultivate algae.
4. Use high-quality feed or high-quality additives to reduce stress-induced pond-wandering in shrimp. Practice has proven that regularly feeding immune polysaccharides, VC + VE, or Shuanghuanglian and Genlian Jiedu San before sudden weather changes can effectively prevent stress-induced pond-wandering in shrimp.
II. Hypoxic pond-wandering
Analysis and diagnosis: During the aquaculture process, when dissolved oxygen in the water body is insufficient, shrimp will swim up in groups to the water surface where dissolved oxygen is higher to breathe oxygen. This phenomenon is hypoxic pond-wandering (commonly known as "floating head"). Pond-wandering caused by hypoxia appears at all stages of aquaculture. This is because pond stocking density is too high, feeding is excessive, pond water deteriorates, and the water color turns green, red, or black; floating head is extremely likely to occur during evening thunderstorms. Pond-wandering mostly occurs in the early morning, sometimes also starting in the first half of the night or even during the day. Farmers can make a diagnosis based on water quality and weather conditions.
Solutions: If shrimp are floating head and pond-wandering, measures should immediately be taken for emergency rescue. 1. Turn on the aerators to increase oxygen; 2. Broadcast chemical oxygen-increasing agents, such as sodium percarbonate; 3. Inject fresh water into the pond and splash glucose + table salt or VC + VE; 4. Stop feeding during the floating head period, and resume feeding only after the oxygen condition has completely improved.
III. Pond-wandering caused by excessive ammonia nitrogen and nitrite
Analysis and diagnosis: In normal aquaculture water, when the nitrite nitrogen content is below 0.1 mg/L (freshwater) or 0.5 mg/L (seawater), and the ammonia nitrogen concentration is below 0.2 mg/L (freshwater) or 0.6 mg/L (seawater), shrimp can live normally without any health damage. However, if these values are exceeded, it will cause reduced activity of multiple enzymes in the shrimp's body, reduce the oxygen-carrying capacity of the blood, damage the epithelial tissue of the gill filaments, lead to poor exchange of oxygen and waste and liver failure, and cause the shrimp to become restless and appear at the pond edge (crawling on sand), or even swim irregularly in groups or scatter-swim at the water surface.
Solutions: 1. Strengthen the management of pond water quality and bottom quality to create a good growth environment for shrimp; 2. When ammonia nitrogen in the shrimp pond is too high, sodium humate + compound Bacillus or photosynthetic bacteria can be used to regulate and lower ammonia nitrogen levels; 3. When nitrite nitrogen exceeds the standard, promptly use chemical preparations that can rapidly reduce nitrite and nitrifying bacteria, or, according to the aging condition of the water body and the level of organic matter in the water, change the water at an appropriate time. If nitrite exceeds the standard severely and shrimp show poisoning symptoms, organic acids or EDTA should also be splashed for detoxification.
IV. Pond-wandering caused by unsuitable pH
Analysis and diagnosis: When the pH value is below 6.5, the shrimp's breathing rhythm accelerates and metabolic rate increases. At the same time, acidic water can lower the pH value of the shrimp's blood, reduce the partial pressure of oxygen in the blood, and cause obstacles in the oxygen transport function of hemoglobin. Similarly, when the pH value is above 9.2, the toxicity of harmful factors in the water body increases, the burden on the shrimp's liver is too heavy, and delayed detoxification leads to poisoning and death by suffocation in the shrimp.
Solutions: At present, many farmers neglect regulation of pond water pH, causing frequent occurrences of shrimp pond-wandering due to unsuitable pH. Therefore, during the aquaculture process, pond water pH should be monitored twice every day (7:00 AM; 4:30 PM). When the water is acidic, quicklime should be used promptly at 8-10 kg per mu/m for 2-3 consecutive days; when the water is alkaline, drain 15-25 cm of pond water, add back 10-15 cm of new water, then treat with a mixture of baking soda + calcium superphosphate at 5-8 kg per mu/m, and then use compound Bacillus + biological fertilizer water agent to stabilize the pH value.
V. Pond-wandering caused by deterioration of the bottom sediment
Analysis and diagnosis: In the middle and late stages of high-density shrimp pond aquaculture, especially in aged shrimp ponds that have been used for shrimp farming for consecutive years without thorough dredging, along with increased feeding, residual feed, feces, and plankton corpses continuously accumulate at the pond bottom, causing deterioration of the bottom sediment and excessive concentrations of harmful indicators such as ammonia nitrogen, nitrite nitrogen, and hydrogen sulfide. In order to avoid the harsh bottom environment, shrimp swim to the middle and upper water layers. This type of pond-wandering has no obvious regularity; there can be both group swimming and scattered swimming, and it may occur at the water surface or in the middle and upper water layers. In severe cases, it can cause mass mortality of shrimp.
Solutions: 1. Normally turn on the aerators to bring residual feed and excrement from the pond bottom to the water surface, so that harmful substances are oxidized into non-toxic substances; 2. Regularly use microecological preparations, such as compound Bacillus, photosynthetic bacteria, or EM bacteria, which can fully utilize the synergistic functional advantages of various strains in compound microorganisms to promptly decompose hidden dangers that worsen the bottom sediment, such as residual feed, excrement, and animal corpses; 3. Sprinkle granular oxygen-increasing agents or bottom-improving agents with oxygen-increasing functions to improve and stabilize the water body.
VI. Pond-wandering caused by disease
Analysis and diagnosis: Shrimp infected with diseases such as red body, white spot, black gill rot, fluorescence, and ciliates can cause pond-wandering. Diseased shrimp show slow swimming or frantic swimming at the water surface, mostly swimming alone rather than in groups, and are often sluggish in response when stimulated. Sometimes they spin at the water surface or swim up and down without direction, and sometimes lie on their sides in shallow water at the pond edge. The most obvious feature is that pond-wandering shrimp often show various typical pathological characteristics on the body surface, gill filaments, hepatopancreas, and gastrointestinal tract. Encountering this situation is a precursor to an outbreak of disease in diseased shrimp. Close observation should be made, diseased shrimp should be carefully examined, and after diagnosis the right medicine should be used to avoid greater economic losses.
Solutions: 1. During periods of high disease incidence, splash Shuanghuanglian or rhubarb extract + compound iodine over the entire pond 1-2 times to inhibit pathogen growth. If ciliates are present, also splash zinc sulfate or matrine preparations; 2. Regularly use microbial preparations such as compound Bacillus + biological fertilizer water agent to maintain the balance of beneficial microbial flora in the pond, generally once every 7-15 days; 3. Frequently use immune polysaccharides, VC + VE, Gandanning, etc. mixed into feed for feeding, and when necessary, feed appropriate amounts of antibiotics at appropriate times (such as florfenicol, enrofloxacin, etc.) to improve shrimp immunity and disease resistance.
VII. Nutritional pond-wandering
Analysis and diagnosis: This is caused by insufficient food organisms in the water body or insufficient feeding, leading to inadequate food intake by shrimp. Pond-wandering caused by starvation mainly appears in the early stage or middle and late stages of aquaculture. In the early stage of aquaculture, shrimp seedlings are relatively small and cannot consume larger pellet compound feed, basically relying mainly on plankton in the water. Especially in ponds with high stocking density, food organisms cannot meet the feeding needs of shrimp. In the middle and late stages of aquaculture, farmers often estimate the amount of shrimp remaining in the pond and the feeding amount with considerable deviation, resulting in insufficient feed being supplied and failure to meet the normal feeding and growth needs of shrimp, causing pond-wandering due to starvation. Diagnostic method: This type of pond-wandering phenomenon has obvious group-swimming behavior, swimming in circles along the pond edge. Examination shows a lack of food in the shrimp's intestines, and the body shows no pathological changes. When some feed is thrown at the pond edge, many shrimp immediately stop and feed.
Solutions: 1. About 10 days before releasing seedlings, splash compound Bacillus + biological fertilizer water agent to fertilize water and cultivate algae, ensuring that there is sufficient basic food when the shrimp seedlings enter the pond; 2. After the shrimp seedlings enter the pond, if the density is relatively high, high-grade feed should also be appropriately fed (such as shrimp flakes, BP, etc.). After one week, once the shrimp seedlings have adapted, mainly feed crushed feed and small feed. At this time, it is advisable to splash over the entire pond with water to ensure that the shrimp seedlings can obtain sufficient food; 3. During the aquaculture process, flexible adjustments should be made according to factors such as the individual size of the shrimp, weather changes, water quality and bottom sediment conditions, shrimp health status, physiological condition, and actual food intake of the shrimp, so as to achieve scientific and reasonable feeding; 4. When starvation pond-wandering occurs, increase the feeding amount, add immune polysaccharides, VC + VE, etc. to the feed, and change water appropriately.
VIII. Physiological pond-wandering
Analysis and diagnosis: On the first and fifteenth days of each lunar month, when the moon waxes and wanes and the tides rise and fall, shrimp become more active according to the patterns of tidal changes. This type of pond-wandering is not very intense, has a certain periodicity and habitual nature, and is accompanied by concentrated molting. This type of pond-wandering belongs to physiological pond-wandering and is generally harmless. However, during the molting period, prevention should be taken against disease in shrimp caused by insufficient dissolved oxygen. In addition, it is recommended to avoid disinfection, insecticide, and fertilization during this period.
Solutions: (1) During pond-wandering, drain more than 20 cm of water, then add 10 cm of water, stop feeding at the same time, and splash active calcium + immune polysaccharides or VC + VE to promote synchronized molting and growth of shrimp; (2) Turn on aerators or broadcast chemical oxygen-increasing agents to increase dissolved oxygen in the water body, such as granular oxygen, to ensure sufficient dissolved oxygen in the pond water.
--------------------------------------
A relatively comprehensive summary
Shrimp pond-wandering refers to a phenomenon in which shrimp exhibit abnormal activities such as slow swimming, sluggish swimming, or group swimming at the water surface, and it is a difficult problem in aquaculture. Because pond-wandering is often accompanied by shrimp mortality, many farmers treat it as a disease. Various medications have been used, but with little effect. The author's analysis of several main causes of the shrimp pond-wandering phenomenon under current environmental conditions and the countermeasures are as follows, for the reference of fellow farmers.
I. Pond-wandering caused by environmental changes
Analysis and diagnosis: After high temperatures, low pressure, strong winds, heavy rain, or typhoons, because the shrimp pond is too shallow, the polluted pond bottom is easily stirred up and made turbid by continuous strong winds and heavy rain. Changes in physicochemical factors in the shrimp pond water environment or excessive levels of toxic factors cause large numbers of beneficial algae to die off, and the pond water suddenly becomes clear or the plankton community composition in the shrimp pond changes (i.e., "algae crash"), leading to deterioration of water quality.
In practice it has also been found that if cloudy and rainy weather lasts for more than 5-7 days, after it clears up the fierce sunlight causes the water to suddenly become dense with algae, and this situation can also cause stress-induced pond-wandering in shrimp.
In ponds where pond-wandering occurs, pathogenic bacterial strains concentrate at the pond bottom and are extremely easily activated and multiplied. At the same time, the shrimp's constitution is weak, providing an opportunity for pathogens to invade, and making disease highly likely to be induced.
Solutions:
1. When weather changes occur, inject new water to raise the water level of the shrimp pond.
2. Before sharp weather changes, splash organic acids or EDTA over the entire pond to degrade toxic components such as heavy metals, increase the permeability of the water body, and create a comfortable environment for the shrimp. Then splash anti-stress preparations, such as glucose + table salt or vitamin C + vitamin E, to enhance the shrimp's anti-stress capacity. If continuous rainfall lasts too long, quicklime can be splashed 1-2 times during the period, applied at 10-12 kg per mu/m.
3. When algae phase changes occur, splash sodium humate or organic acids, and the next day splash microbial preparations over the entire pond, such as compound Bacillus, photosynthetic bacteria, or EM bacteria. If the water body is clear to the bottom, a multi-element biological fertilizer can be used to cultivate algae.
4. Use high-quality feed or high-quality additives to reduce stress-induced pond-wandering in shrimp. Practice has proven that regularly feeding immune polysaccharides, VC + VE, or Shuanghuanglian and Genlian Jiedu San before sudden weather changes can effectively prevent stress-induced pond-wandering in shrimp.
II. Hypoxic pond-wandering
Analysis and diagnosis: During the aquaculture process, when dissolved oxygen in the water body is insufficient, shrimp will swim up in groups to the water surface where dissolved oxygen is higher to breathe oxygen. This phenomenon is hypoxic pond-wandering (commonly known as "floating head"). Pond-wandering caused by hypoxia appears at all stages of aquaculture. This is because pond stocking density is too high, feeding is excessive, pond water deteriorates, and the water color turns green, red, or black; floating head is extremely likely to occur during evening thunderstorms. Pond-wandering mostly occurs in the early morning, sometimes also starting in the first half of the night or even during the day. Farmers can make a diagnosis based on water quality and weather conditions.
Solutions: If shrimp are floating head and pond-wandering, measures should immediately be taken for emergency rescue. 1. Turn on the aerators to increase oxygen; 2. Broadcast chemical oxygen-increasing agents, such as sodium percarbonate; 3. Inject fresh water into the pond and splash glucose + table salt or VC + VE; 4. Stop feeding during the floating head period, and resume feeding only after the oxygen condition has completely improved.
III. Pond-wandering caused by excessive ammonia nitrogen and nitrite
Analysis and diagnosis: In normal aquaculture water, when the nitrite nitrogen content is below 0.1 mg/L (freshwater) or 0.5 mg/L (seawater), and the ammonia nitrogen concentration is below 0.2 mg/L (freshwater) or 0.6 mg/L (seawater), shrimp can live normally without any health damage. However, if these values are exceeded, it will cause reduced activity of multiple enzymes in the shrimp's body, reduce the oxygen-carrying capacity of the blood, damage the epithelial tissue of the gill filaments, lead to poor exchange of oxygen and waste and liver failure, and cause the shrimp to become restless and appear at the pond edge (crawling on sand), or even swim irregularly in groups or scatter-swim at the water surface.
Solutions: 1. Strengthen the management of pond water quality and bottom quality to create a good growth environment for shrimp; 2. When ammonia nitrogen in the shrimp pond is too high, sodium humate + compound Bacillus or photosynthetic bacteria can be used to regulate and lower ammonia nitrogen levels; 3. When nitrite nitrogen exceeds the standard, promptly use chemical preparations that can rapidly reduce nitrite and nitrifying bacteria, or, according to the aging condition of the water body and the level of organic matter in the water, change the water at an appropriate time. If nitrite exceeds the standard severely and shrimp show poisoning symptoms, organic acids or EDTA should also be splashed for detoxification.
IV. Pond-wandering caused by unsuitable pH
Analysis and diagnosis: When the pH value is below 6.5, the shrimp's breathing rhythm accelerates and metabolic rate increases. At the same time, acidic water can lower the pH value of the shrimp's blood, reduce the partial pressure of oxygen in the blood, and cause obstacles in the oxygen transport function of hemoglobin. Similarly, when the pH value is above 9.2, the toxicity of harmful factors in the water body increases, the burden on the shrimp's liver is too heavy, and delayed detoxification leads to poisoning and death by suffocation in the shrimp.
Solutions: At present, many farmers neglect regulation of pond water pH, causing frequent occurrences of shrimp pond-wandering due to unsuitable pH. Therefore, during the aquaculture process, pond water pH should be monitored twice every day (7:00 AM; 4:30 PM). When the water is acidic, quicklime should be used promptly at 8-10 kg per mu/m for 2-3 consecutive days; when the water is alkaline, drain 15-25 cm of pond water, add back 10-15 cm of new water, then treat with a mixture of baking soda + calcium superphosphate at 5-8 kg per mu/m, and then use compound Bacillus + biological fertilizer water agent to stabilize the pH value.
V. Pond-wandering caused by deterioration of the bottom sediment
Analysis and diagnosis: In the middle and late stages of high-density shrimp pond aquaculture, especially in aged shrimp ponds that have been used for shrimp farming for consecutive years without thorough dredging, along with increased feeding, residual feed, feces, and plankton corpses continuously accumulate at the pond bottom, causing deterioration of the bottom sediment and excessive concentrations of harmful indicators such as ammonia nitrogen, nitrite nitrogen, and hydrogen sulfide. In order to avoid the harsh bottom environment, shrimp swim to the middle and upper water layers. This type of pond-wandering has no obvious regularity; there can be both group swimming and scattered swimming, and it may occur at the water surface or in the middle and upper water layers. In severe cases, it can cause mass mortality of shrimp.
Solutions: 1. Normally turn on the aerators to bring residual feed and excrement from the pond bottom to the water surface, so that harmful substances are oxidized into non-toxic substances; 2. Regularly use microecological preparations, such as compound Bacillus, photosynthetic bacteria, or EM bacteria, which can fully utilize the synergistic functional advantages of various strains in compound microorganisms to promptly decompose hidden dangers that worsen the bottom sediment, such as residual feed, excrement, and animal corpses; 3. Sprinkle granular oxygen-increasing agents or bottom-improving agents with oxygen-increasing functions to improve and stabilize the water body.
VI. Pond-wandering caused by disease
Analysis and diagnosis: Shrimp infected with diseases such as red body, white spot, black gill rot, fluorescence, and ciliates can cause pond-wandering. Diseased shrimp show slow swimming or frantic swimming at the water surface, mostly swimming alone rather than in groups, and are often sluggish in response when stimulated. Sometimes they spin at the water surface or swim up and down without direction, and sometimes lie on their sides in shallow water at the pond edge. The most obvious feature is that pond-wandering shrimp often show various typical pathological characteristics on the body surface, gill filaments, hepatopancreas, and gastrointestinal tract. Encountering this situation is a precursor to an outbreak of disease in diseased shrimp. Close observation should be made, diseased shrimp should be carefully examined, and after diagnosis the right medicine should be used to avoid greater economic losses.
Solutions: 1. During periods of high disease incidence, splash Shuanghuanglian or rhubarb extract + compound iodine over the entire pond 1-2 times to inhibit pathogen growth. If ciliates are present, also splash zinc sulfate or matrine preparations; 2. Regularly use microbial preparations such as compound Bacillus + biological fertilizer water agent to maintain the balance of beneficial microbial flora in the pond, generally once every 7-15 days; 3. Frequently use immune polysaccharides, VC + VE, Gandanning, etc. mixed into feed for feeding, and when necessary, feed appropriate amounts of antibiotics at appropriate times (such as florfenicol, enrofloxacin, etc.) to improve shrimp immunity and disease resistance.
VII. Nutritional pond-wandering
Analysis and diagnosis: This is caused by insufficient food organisms in the water body or insufficient feeding, leading to inadequate food intake by shrimp. Pond-wandering caused by starvation mainly appears in the early stage or middle and late stages of aquaculture. In the early stage of aquaculture, shrimp seedlings are relatively small and cannot consume larger pellet compound feed, basically relying mainly on plankton in the water. Especially in ponds with high stocking density, food organisms cannot meet the feeding needs of shrimp. In the middle and late stages of aquaculture, farmers often estimate the amount of shrimp remaining in the pond and the feeding amount with considerable deviation, resulting in insufficient feed being supplied and failure to meet the normal feeding and growth needs of shrimp, causing pond-wandering due to starvation. Diagnostic method: This type of pond-wandering phenomenon has obvious group-swimming behavior, swimming in circles along the pond edge. Examination shows a lack of food in the shrimp's intestines, and the body shows no pathological changes. When some feed is thrown at the pond edge, many shrimp immediately stop and feed.
Solutions: 1. About 10 days before releasing seedlings, splash compound Bacillus + biological fertilizer water agent to fertilize water and cultivate algae, ensuring that there is sufficient basic food when the shrimp seedlings enter the pond; 2. After the shrimp seedlings enter the pond, if the density is relatively high, high-grade feed should also be appropriately fed (such as shrimp flakes, BP, etc.). After one week, once the shrimp seedlings have adapted, mainly feed crushed feed and small feed. At this time, it is advisable to splash over the entire pond with water to ensure that the shrimp seedlings can obtain sufficient food; 3. During the aquaculture process, flexible adjustments should be made according to factors such as the individual size of the shrimp, weather changes, water quality and bottom sediment conditions, shrimp health status, physiological condition, and actual food intake of the shrimp, so as to achieve scientific and reasonable feeding; 4. When starvation pond-wandering occurs, increase the feeding amount, add immune polysaccharides, VC + VE, etc. to the feed, and change water appropriately.
VIII. Physiological pond-wandering
Analysis and diagnosis: On the first and fifteenth days of each lunar month, when the moon waxes and wanes and the tides rise and fall, shrimp become more active according to the patterns of tidal changes. This type of pond-wandering is not very intense, has a certain periodicity and habitual nature, and is accompanied by concentrated molting. This type of pond-wandering belongs to physiological pond-wandering and is generally harmless. However, during the molting period, prevention should be taken against disease in shrimp caused by insufficient dissolved oxygen. In addition, it is recommended to avoid disinfection, insecticide, and fertilization during this period.
Solutions: (1) During pond-wandering, drain more than 20 cm of water, then add 10 cm of water, stop feeding at the same time, and splash active calcium + immune polysaccharides or VC + VE to promote synchronized molting and growth of shrimp; (2) Turn on aerators or broadcast chemical oxygen-increasing agents to increase dissolved oxygen in the water body, such as granular oxygen, to ensure sufficient dissolved oxygen in the pond water.
--------------------------------------
A relatively comprehensive summary