| Penaeus vannamei is native to the waters along the Pacific coast of South America.It is more concentrated in the waters near Ecuador.It has a wide range of salinity adaptation,fast growth speed and high economic value.It is one of the most important economic shrimps in the world.The global output in 2018 was 4.9662 million tons.Since it was introduced into China for 30 years,it has attracted much attention because of its fast growth speed,high yield,wide adaptability to salt and temperature,good economic benefits of breed and mature breeding technology.At present,the breeding output of Penaeus vannamei in China is 1862900 tons,ranking first in the world.In coastal areas,high pool,factory and small shed are the main breeding and production modes of Penaeus vannamei.With the maturity and popularization of Penaeus vannamei desalination technology,the nursery in coastal areas airlift the shrimp seedlings inland.After artificial desalination and roughening,Penaeus vannamei can be cultured in the fresh water of the outer pond.This model and scale have developed rapidly in recent years.Ankang,Shaanxi Province is one of the most advantageous areas in terms of fishery production resources in Shaanxi Province,abundant water resources,rivers and lakes,ponds and reservoirs,mild climate and great potential for fishery development.In recent years,Ankang fishery has continuously changed its development mode and actively introduced famous,special and excellent aquatic products such as paddlefish and California perch.Penaeus vannamei has attracted much attention because of its short breeding cycle and high economic and social benefits.After investigation and analysis,Combined with the comprehensive evaluation of pond hydrometeorological data accumulated for many years by Ankang aquatic experimental demonstration station of Northwest A&F University(Referred to as"test station")it is considered that there are basic conditions for desalination culture of Penaeus vannamei in the outer pond.From 2019 to 2021,In test station three desalination culture experiments of Penaeus vannamei were carried out once a year.Test 1.In the first year,from May 13 to August 10,2019,chlorine dioxide was used to clear and disinfect the pond in the early stage of breeding,and the plankton was cultured with fertilizer and water paste and fermented peptide source.Before seedling release,1 ton of sea salt was added to adjust the salinity of the pond to 1.1‰.In 3.2×667m~2full cement pond used 60000 shrimps diluted to 1.5‰for 89 days,an average of 18750shrimps are put in per mu,place two circular feeding tables with a diameter of 60 cm at the upper and lower tuyeres of the pond to observe feeding,feed 2～3 times according to the daily feeding conditions,fed 230 kg(CP38%,EE3.0%),and produced 91.7 kg of fresh prawns with an average specification of 92/kg,with a yield of 28.65 kg per mu,a survival rate of 14.06%and the feed coefficient is 2.51.During the breeding period,the water temperature is 23.5℃～30.5℃,the salinity is 1.5‰～0.1‰,the total alkalinity is135mg/L～67.5mg/L,and the p H is 8.2～9.6,ammonia nitrogen≤0.1,nitrite≤0.005.In this experiment,the large range of p H change in the physical and chemical indexes of water body and more wild miscellaneous fish are the main reasons for the low survival rate and yield of this experiment;Test 2.In the second year,from July 19 to September 30,2020,lime slurry and tea meal will be used to clear the pond in the early stage of breeding,and chlorine dioxide will be used to disinfect the water after entering the water.When the weather is sunny,Chlorella species,phosphate fertilizer and fermentation peptide sources will be used to cultivate plankton in the pond,and 0.5 tons of sea salt will be added before seedling release to adjust the salinity of the pond to 0.6‰.In 1.3×667m~2slope free pond uses 30000 shrimps diluted to 0.7‰for 73 days,an average of 23077 shrimps are put in per mu,place two circular feeding tables with a diameter of 60 cm at the upper and lower tuyeres of the pond to observe feeding,feed 2～3 times according to the daily feeding conditions,feeds 180 kg(CP38%,EE3.0%),and produces an average of 122 shrimps/kg,60.5 kg of fresh shrimps,with a yield of 46.53 kg per mu,a survival rate of 24.6%and the feed coefficient is 2.98.During the breeding period,the water temperature is 18.5℃～30℃,the salinity is 0.7‰～0.1‰,the total alkalinity is 135mg/L～67.5mg/L,and the p H is 7.6～8.6,ammonia nitrogen≤0.2,nitrite≤0.005.The main reason for the low survival rate and yield of this experiment was the sudden change of climate in the later stage of breeding,the sudden drop of water temperature to 18.5℃,the death of algae in the pond and the stress casualties of shrimp;Test 3.In the third year,from May 25 to September 15,2021,after drying the pond and drying the pond,sprinkle quicklime for ploughing and mixing,clean the pond with lime slurry and tea meal after entering the water,extract the upper water of the pond next door and introduce it into phytoplankton,then disinfect it with chlorine dioxide,use amino acid fertilizer paste,phosphorus fertilizer,fermented lactic acid bacteria solution and fermented peptide source to cultivate pond plankton and supplement beneficial microorganisms,and add 1 ton of sea salt to adjust the salinity of the pond to 1.5‰before seedling release.At2.0×667m~2earth pond uses 60000 shrimps diluted to 1.9‰for 114 days,an average of30000 shrimps are put in per mu,place two circular feeding tables with a diameter of 60 cm at the upper and lower tuyeres of the pond to observe feeding,feed 2～3 times according to the daily feeding conditions,feeds 478kg(CP38%,EE3.0%),and produces 423.25kg fresh prawns with an average specification of 80/kg.The yield per mu is 211.62kg,the survival rate is 56.43%,and the feed coefficient is 1.13.During the breeding period,the water temperature is 24℃～31.5℃,the salinity is 1.5‰～0.3‰,the total alkalinity is157.5mg/L～90mg/L,and the p H is 8.2～8.6,ammonia nitrogen≤0.2,nitrite≤0.005.The survival rate and yield of the desalination culture experiment in the outer pond are significantly higher than those in the previous two years.The main reason is that the physical and chemical indexes of the culture water environment are stable,the water temperature is appropriate,and the culture environment meets the growth needs of shrimp.To sum up,three desalination culture experiments of Penaeus vannamei were carried out in the experimental station,and the survival rate and yield per mu increased year by year.It is considered that the stable balance of aquaculture water environment is the key to the desalination culture technology of Penaeus vannamei in the outer pond.It is suggested that the desalination culture of Penaeus vannamei in the outer pond of Ankang area should avoid the climate interference in early spring and late autumn,and use the best temperature and water temperature from June to September every year to carry out aquaculture production.The pond with small area of mud bottom(≤8 mu)shall be selected.The pond and sun pond shall be dried thoroughly before releasing the seedlings,and the bottom of the pond shall be ploughed.After entering the water,all wild miscellaneous fish and aquatic insects in the pond shall be cleaned and killed,and the salinity of the aquaculture water body shall be adjusted to the desalination salinity level of shrimp seedlings(<2‰);The suitable seedling density is 28000～37000 tails/mu;Daily management is based on stabilizing the physical and chemical indexes of water body,and high-grade and full price compound feed is used for breeding in the whole process. |
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