Common Abnormal Phenomena in Whiteleg Shrimp Farming and Their Management
Abnormal phenomenon 1: Before stocking, the pond water cannot be fertilized despite repeated fertilization, or the water color is very poor. (1) Causes: Serious exceedance of toxic substances such as heavy metal ions, or massive reproduction of harmful bacteria and zooplankton in the pond, or growth of filamentous algae and blue-green algae (qingni moss) in the pond, or severe aging of the pond, acidification and hardening of the pond bottom, and stagnation of material exchange between the pond water and bottom mud, which inhibits the growth of plankton. (2) Treatment methods: 1) Sun-dry the pond bottom, thoroughly disinfect with quicklime, tea seed cake and other agents, or plant forage grass on the pond bottom after drying the pond; 2) Splash detoxifying water-culturing agent or detoxifying agent and other agents over the whole pond; 3) For ponds with growth of filamentous algae and blue-green algae, kill them with chelated copper or chongzaojing and other agents; 4) Apply fermented organic fertilizer or inorganic fertilizer to cultivate the water.
Abnormal phenomenon 2: Shrimp fry grow slowly, body color is dull, molting is difficult, and sizes are uneven. (1) Causes: Poor quality of fry or malnutrition. (2) Treatment methods: 1) Regularly splash water-regulating king or probiotics and other microbial preparations to condition the water quality; 2) Choose high-quality feed and feed scientifically and reasonably; add aquatic multivitamins or aquatic nutrition elements and other nutritional additives to the feed; 3) Supplement once a week with animal-based feed such as small trash fish, snails, mussels, and clam meat.
Abnormal phenomenon 3: In the early stage of farming, the pond water appears earthy yellow, grayish white, etc., and is turbid. (1) Causes: The dominant population of phytoplankton easily digested by shrimp in the pond water is consumed, and algae not easily digested by shrimp reproduce in large numbers. (2) Treatment methods: 1) First splash chlorine-containing or iodine-containing disinfectants over the whole pond; 2) Replace part of the old water, add new water, and adjust the plankton population; 3) Apply an appropriate amount of fertilizer, or splash concentrated bacteria-algae liquid and other ecological nutrient agents over the whole pond.
Abnormal phenomenon 4: In the middle and late stages of farming, dead shrimp appear at the bottom of the pond. (1) Causes: Insufficient dissolved oxygen at the bottom of the shrimp pond, environmental deterioration, and accumulation of large amounts of toxic and harmful substances; the shrimp themselves are malnourished, have poor resistance, and have difficulty molting. (2) Treatment methods: 1) Improve the shrimp's living environment and increase the dissolved oxygen content of the pond water; 2) Mix and dilute povidone-iodine and Baidu decoction and splash them, replace an appropriate amount of water after 24 hours, and use EM bacteria and others to regulate water quality; 3) Mix liver-protecting heme, Ganweibao, immune polysaccharides, vitamin C and others into the feed and feed for 5 consecutive days.
Abnormal phenomenon 5: The pond water is viscous and greasy, has foam, has extremely low transparency, and appears dark green or reddish brown. (1) Causes: Leftover bait and residual feed after heavy feeding and shrimp excrement sink to the bottom of the pond, causing the water quality to become excessively fertile and deteriorated. (2) Treatment methods: 1) Splash chlorine dioxide, virus-clearing agent and other disinfectants over the whole pond; 2) Splash Bacillus, Lishuisu and other microbial preparations over the whole pond to purify water quality; 3) Use water purifying agents, bottom-improving king and other agents for adsorption and precipitation.
Abnormal phenomenon 6: Shrimp swim along the pond edge, have soft shells, red bodies, and die in large numbers. (1) Causes: Toxic substances such as nitrite, ammonia nitrogen, and hydrogen sulfide in the water exceed standards. (2) Treatment methods: 1) Splash Bacillus subtilis or Bacillus and other microecological preparations over the whole pond, and simultaneously mix live bacterial preparations into the feed; 2) Use water quality improvers (such as zeolite powder, activated carbon, clay, etc.); 3) Reasonably replenish or exchange water and correctly use aerators.
Abnormal phenomenon 7: In the late stage of farming, a layer of emerald green water bloom floats on the water surface at the downwind area of the shrimp pond. (1) Causes: The high nitrogen content of organic matter in the pond water and the slightly alkaline water (pH 8-9.5) cause massive reproduction of cyanobacteria not easily digested by shrimp, making them the dominant population of phytoplankton. (2) Treatment methods: 1) Frequently add clean water, regulate water quality, control algae reproduction, and regularly treat pond water with EM bacteria, photosynthetic bacteria, etc.; 2) When cyanobacteria reproduce massively in the pond, choose a sunny midday to discharge pond water at the downwind area and lower the water level as much as possible, generally to about 1/3 of the pond water, then splash a mixture of copper sulfate and ferrous sulfate or algae-killing king over the whole pond; 3) Use a fine-mesh silk screen at the downwind water surface of the pond to remove cyanobacteria, or locally splash a mixture of copper sulfate and ferrous sulfate to kill cyanobacteria.
Abnormal phenomenon 8: The water color suddenly turns black, white, or red, and the pond water is turbid. (1) Causes: Caused by seasonal changes or shifts in wind direction, commonly known as “algae collapse”. (2) Treatment methods: 1) Splash water purifying agents, detoxifying water-purifying king and others over the whole pond to purify water quality; 2) Use detoxifying treasure, detoxifying water-culturing treasure and other agents to stabilize water quality; 3) Splash concentrated bacteria-algae liquid and other ecological nutrient agents over the whole pond to restore water color.
Abnormal phenomenon 9: Shrimp are anorexic or refuse to eat. (1) Causes: Hot, stuffy, and continuously rainy weather puts the shrimp in a state of stress. (2) Treatment methods: 1) Deepen the water level and reduce feeding; 2) Use bottom quality improvers such as detoxifying water-purifying king, high-efficiency water-purifying treasure, and bottom-improving king; 3) Splash pond detoxifying agents such as detoxifying treasure and detoxifying water-culturing treasure; 4) Apply oxygen-increasing agents; 5) Strengthen nutrition to promote shrimp feeding, and mix Yangkang, aquatic nutrition elements, and liver-protecting tai into the feed.
Abnormal phenomenon 10: Shrimp often have white or dark blue spots on the chest and abdomen. In the late stage of disease, white spots appear under the shrimp body's skin, shell, and appendages, or the shell softens, the cephalothorax shell is easily peeled off, and the shell separates from the dermis. (1) Causes: White spot disease caused by a virus. (2) Treatment methods: 1) Fry must pass virus testing and be confirmed virus-free before entering the farming pond; 2) Feed high-quality complete feed, and add immune polysaccharides, ginsenosides, and stabilized vitamin C to the feed; 3) Splash bromochlorohydantoin or dibromohydantoin over the whole pond once every 5-7 days; 4) During the farming season, splash quaternary ammonium salt complexed iodine over the whole pond once every 15 days; 5) Use biological preparations to maintain a stable water environment.
Abnormal phenomenon 11: Shrimp appendages turn red (more obvious on swimming legs), and the gill area of the cephalothorax appears yellow. Sick shrimp often wander along the pond edge and are anorexic. (1) Causes: Red leg disease caused by Vibrio infection. (2) Treatment methods: 1) Before shrimp stocking, pond clearing treatment must be carried out; 2) In high-temperature seasons, regularly splash photosynthetic bacteria and activated zeolite powder into the farming water; 3) Splash dichlorohydantoin or bromochlorohydantoin over the whole pond; 4) While applying external medication, orally administer Shaduling or Difenicoli.
Abnormal phenomenon 12: Filamentous fungi grow on the shrimp's gill filaments, appendage setae, and swimming legs, and in severe cases can also be seen on the shell surface. This affects the shrimp's respiratory function, causing slow growth and easy death from hypoxia. (1) Causes: Caused by Mucor lucens (Leucothrix mucor) and Thiothrix, mainly related to deterioration of the farming environment, water quality, and bottom quality, and usually occurs when the pond water is eutrophic. (2) Treatment methods: 1) Maintain good water quality and bottom quality, and thoroughly clear the pond before stocking; 2) Do not stock at too high a density, and appropriately increase water exchange; 3) Add an appropriate amount of molting hormone to the feed to promote normal molting and growth of shrimp; 4) Splash quaternary ammonium salt complexed iodine over the whole pond; 5) Splash tea seed cake over the whole pond, and after the sick shrimp molt, carry out a large water exchange.
Abnormal phenomenon 13: The shrimp digestive tract appears red, some shrimp stomachs also appear red, the midgut turns red and swells, and the rectum appears turbid with unclear boundaries. Sick shrimp have reduced vitality, are anorexic, and grow slowly. (1) Causes: Enteritis caused by Aeromonas hydrophila infection. (2) Treatment methods: 1) Splash dibromohydantoin over the whole pond, and after 3 days splash nitrifying bacteria over the whole pond; 2) Add Changyanting and allicin to the feed and feed continuously for 3-5 days.