| In this experiment,different cultivation area for Litopenaeus vannamei were selected,the effects of different cultivation area on growth,survival,and the feed coefficient for Litopenaeus vannamei were discussed.At the same time,analyzing the characteristics of the breeding cycle water index change,Litopenaeus vannamei circumstance to the terminal and economic benefits.1 Effects of different pond area on growth of Litopenaeus vannameiSelected 3,335 m~2、5,336 m~2、6,670 m~2 three area of the pond,each area of set of two ponds.The pond shrimp seedlings stocking density shall be carried out in accordance with the 25,000/667 m~2.From the seedling day,each 10 days measuring body length and weight of every pond.After 90 days,the body length and body weight of Litopenaeus vannamei in different ponds had significant difference(P<0.05).The average final body length of Litopenaeus vannamei in 3,335 m~2 pond was 14.42 cm/tail,The average final body weight of Litopenaeus vannamei was 22.51 g/tail,which was significantly higher than that of 5,336 m~2 and 6,670 m~2 ponds(P<0.05).The specific growth rate and specific weight gain rate in 3,335 m~2 pond were significantly higher than those of 5336 m~2 and 6,670 m~2 pond(P<0.05).The feed coefficient had significant difference among the three different area ponds(P< 0.05).The feed coefficient of 6,670 m~2 was significantly lower than that of 3,335m~2 and 5,336m~2,and the feed coefficient was 0.90.The feed coefficient in 5,336 m~2 pond was 0.93,which was the second.The highest feed coefficient appeared in 3,335 m~2 pond,which was 0.98.The survival rate of Litopenaeus vannamei in 6,670 m~2 pond was 85.40%,which was significantly higher than that of 3,335 m~2 and 5,336 m~2 ponds(P<0.05).and the survival rate of Litopenaeus vannamei had no significant difference between in 3,335 m~2 pond and in 5,336 m~2 pond(P>0.05).It was 75.52% and 79.87% respectively.The experimental results show that the 3,335 m~2 pond has obvious advantages in the growth of Litopenaeus vannamei.2.Effects of different pond area on disease of Litopenaeus vannameiDuring the breeding period,no disease was found in each pond.In the late period of culture,Litopenaeus vannamei appeared to die secretly.The main symptoms were: red shrimp body and appendages,empty stomach,translucent muscles,which all appeared in small individuals.After the incidence was found,measures such as controlling feed quantity,changing water and bottom were taken.It could inhibit the expansion of the disease range and no large-scale death.3 Changes of water quality indexes in different areas pondsIn the whole experimental period,physical and chemical indexes were monitored every 5 days,including water temperature,p H,dissolved oxygen,ammonia nitrogen concentration and nitrite concentration.Dominant species composition of algae was measured every 7 days.In the breeding cycle,the temperature ranges in 3,335 m~2、5,336 m~2 and 6,670 m~2 ponds are 22.0~30.5℃,21.4~30℃ and 20.7~29.5℃,respectively.The p H range was from 8.6 to 8.9.The variation range of dissolved oxygen content was 5.4~9.7 mg/L,5.5~9.0 mg/L,5.8~8.4 mg/L.The fluctuation range of water temperature,p H and dissolved oxygen were suitable for growth of Litopenaeus vannamei.With the extension of culture time,Litopenaeus vannamei individuals grew.feed quantity increased,concentration of ammonia nitrogen and nitrite in ponds increased in the late period of culture.And concentration of ammonia nitrogen in the 5,336 m~2 and 6,670 m~2 ponds did not change during the whole test period and were in a stable state.However concentration of the ammonia nitrogen in 3,335 m~2 pond rose sharply at 65 days,suddenly reached to 0.5 mg/L.The concentrations of nitrite in 3,335 m~2、5,336 m~2 and 6,670 m~2 ponds varied from 0-0.3 mg/L,0.1~0.15 mg/L and 0-0.1 mg/L.The fluctuation range of nitrite concentrations in 3,335 m~2 pond was larger than that of 5,336 m~2 and 6,667 m~2.After harmful index were detected,measures such as water change and water quality improver are taken in time to effectively control the concentrations of ammonia nitrogen and nitrite in each culture pond,which has no serious impact on the growth of cultured Litopenaeus vannamei.In the early stage of culture,diatom and green algae were the dominant species;In the middle and late stage of culture,green algae were the dominant species,followed by diatom,eukaryotes and cryptoalgae,a small amount of dinoflagellate and cyanobacteria,and they were stable in the middle and late stage of culture.High quality algae not only provided natural bait for Litopenaeus vannamei in the early stage of culture,but also played a positive role in maintaining the water quality stability in the middle and late stage of culture.4 Cost and economic benefits of different pondsFeed became the largest cost item in variable costs.The proportion of feed expenditure in each pond ranged from 37 % to 42%.The feed expenditure per 667 m~2 of 3,335 m~2 pond was significantly higher than that of 5,336 m~2 and 6,670 m~2 pond(P<0.05).There was no significant difference between 5,336 m~2 and 6,670 m~2 pond(P>0.05).In terms of drug expenditure and electricity expenditure,there were significant differences among the three types of ponds(P<0.05).The highest drug and electricity expenditure was in 3335m~2 pond,which was 560 yuan/667m~2,440 yuan/667m~2,respectively,followed by 5336 m~2 pond and the cost in 6670 m~2 pond was the lowest.In terms of fixed cost,the rent expenditure per 667m~2 was 1600 yuan,which was the second largest expenditure item of the total cost.the rent of each pond accounted for 20-22% of the total cost.Shrimp fry,feed and pond rent were important parts of the cost of cultivation,accounting for 80-90% of the total.The total production cost of 3,335 m~2、5,336 m~2 and 6,670 m~2 had significant difference(P<0.05).The total production cost of 3335 m~2 was 7620 yuan/667 m~2,which was significantly higher than that of 5,336 m~2 and 6,670 m~2.During the whole cycle,the yield of 3,335 m~2 pond was 850.11 kg /667m~2,the average body weight of each individual was 22.51g/tail,and the net profit reached 12,307.96 yuan /667m~2.The yield,final body weight and net profit were significantly higher than those of 5,336 m~2 and 6,670 m~2 ponds(P<0.05).The results showed that the best yield,the best growth rate and the best economic benefit were obtained in 3,335 m~2 pond.The second was 5,336 m~2 pond,and the lowest contribution rate was 6,670 m~2 pond.It showed that in this study,the input and output was higher and profitability was stronger in the 3335 m~2 ponds.Growth index of Litopenaeus vannamei was combined,The 3335 m~2 pond had the best growth performance.Experimental results show that in three different area of the pond,Key points and prospect of fined-culture pond of Litopenaeus vannamei,the 3,335 m~2 pond has the best growth and the highest economic benefit.5 The main technical points,achieved aquiculture pond and prospectsAccording to the actual situation of Litopenaeus vannamei,to summarize the successful breeding experience of shrimp,the characteristics of shrimp cultivation in Tianjin area,the key points of pond culture of Litopenaeus vannamei were summarized.The control from the two aspects of the standard of shrimp seedling and the culture in the outer pond were detailed,and the trend of shrimp cultivation in Tianjin area was prospected. |
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