| The method of nursery and temporary culture feed on live prey can get shrimps with better quality, it is a method worth of further research and promotion that has an important significance for the sustaining development of the Litopenaeus vannamei cultivation. However, studies and application of feed on live prey method is short, there are still some drawbacks, worth aquaculture researchers to explore, research, and to improve its processes. In this paper, in order to optimize the technological process of Litopenaeus vannamei nursery and temporary culture feed on live prey I carried out these experiments, the results are as follows:1 The effects of feeding various forage prescription on Litopenaeus vannamei nurseryThe research set six treatments of different live prey content diets,are the whole live prey group,80% live prey group,60% live prey group,40% live prey group,20% live prey group, whole compound feed group, other conditions are the same, observe and records the impact of feeding various forage prescription on the vannamei nursery.Experiments were carried out two times, in the first experiment,40% more contrast the proportion of bio-food group and 20% the proportion of live prey group, the former groups compared to following groups are nearly 10 times better in the average survival rate, Zoea to Mysis metamorphosis speed are nearly 20% faster; in the second experiment, all biological food group and 80% live prey group is 2.6 times better than the 60% and 40% bio-food group in final average survival rate, and 60% and 40% bio-food group are nearly 16 times better than the 20% diet group and whole organisms feed group in average survival rate.The results show that:the proportion of live prey during Zoea should not be less than 40%, in order to ensure a better survival rate and abnormal speed; ensure the proportion of more than 80% live prey can get the fastest speeds and highest survival rate of abnormal results; the proportion of live prey less than 20% would have serious implications on the speed of metamorphosis and survival rate. I recommended that at least 40% the proportion of live prey will be needed in the production, according to the comprehensive consideration of cost, practical effects, increase the amount of feeding live prey. Mysis more dependent on the circumstances of the physical strength in Zoea, chose the proper feeding mode selection based on Zoea quality, it is recommended to feed not less than 20% proportion of live prey.2 Formaldehyde treatment on Brachionus plicatilis before getting in the poolThe experiment study on the situation of rotifers tolerate formaldehyde, the effect of formaldehyde treatment on protozoa, the recovery situation of protozoa after treatment, the experimental set blank rotifer culture medium,300ml/m3 formaldehyde-treated group,400 ml/m3 formaldehyde-treated group,500 ml/m3 formaldehyde treatment group,600 ml/m3 formaldehyde treated group, the treatment time is 1min30s; observed, recorded for the survival of rotifers and two protozoa process in each treatment group, evaluate the treatment effect. Diluting the treated culture broth after the treatment, observe the recover situation of protozoa was.After 1.5min treatment of 500ml/m3 and 600ml/m3 of formaldehyde, the death of the individual rotifer is about 1.8 times of the untreated group,300ml/m3 and 400ml/m3 group, reaching about 20% rotifer mortality; 400ml/m3 of formaldehyde can kill more than 99% of the protozoa,500ml/m3 or more concentrations of formaldehyde can completely kill all the protozoa; stable number of death protozoa will be return within 6h, and the 300ml/m3 group protozoan resumes 190 times, 400ml/m3 group will resume 75 times,500ml/m3 or more groups do not have protozoa recovery.The results showed that:there can be a short rotifer treatment with formaldehyde in lmin30s before entering the pool, and then rinsed by fresh water, the concentration of 400～600ml/m3 is appropriate, considering the mortality of rotifers and the effection of killing the protozoa, according to their actual situation to select the appropriate concentration.3 The effects of feeding various forage prescription on vannamei temporary cultureThe research set six treatments of various forage prescription,are the whole live prey group,80% live prey group,60% live prey group.40% live prey group,20% live prey group, whole compound feed group, other conditions are the same, observe and records the impact of feeding various forage prescription on the vannamei temporary culture.The body length of groups with more than 40% live prey was significantly greater than 20% live prey group (P<0.05), the body length of 20% live prey group was significantly greater than the whole compound feed group (P<0.05); groups with more than 60% live prey survival rate was significantly higher than the groups with less than 40% live prey (P<0.05); the difference between the low-temperature resistance groups was not significant (P> 0.05); groups with more than 40% live prey was significantly greater than the proportion of 20% or whole compound feed group in swimming fatigue (P<0.05).The results show that:feeding more than 80% of live prey ratio can get the best results on the growth rate, survival rate, resistance and vitality in all aspects; more than 40% of live prey ratio can achieve the best results on the growth rate and viability,but survival rate and resistance will decline; less than 20% of live prey ratio t will affect the quality of shrimp larvae. I recommended that at least 40% of live prey is needed, and as the case may be appropriate to increase the proportion of live prey.4 The effects of temperature fluctuations on the vannamei temporary cultureThe research set three treatments of different temperature fluctuations,are the constant temperature group,±1℃ fluctuations group,±2℃ fluctuations, and the remaining conditions are the same, observe and record the effects of different temperature fluctuations to the survival rate and growth rate during temporary culture, and designed the cryogenic resistance experiment to compare with different treatment groups.The body length of constant temperature group are higher than the two temperature fluctuations groups, which was significantly greater than,±2℃ fluctuations group (P<0.05); the survival rate difference between the groups was not significant (P> 0.05); fluctuations group slightly higher than the thermostat group in resistance, but the difference between the treatment groups was not significant (P> 0.05).The results showed that:there is no significant impact when temperature fluctuate over than 1℃ for larvae survival rate of vannamei shrimp, but the temperature fluctuations will affect the growth rate of shrimp larvae, and the greater the temperature fluctuate, the slower growth rate will be; and temperature fluctuations resistance groups were slightly higher than the thermostat in cryogenic resistance. Taken together, I is recommended in temporary culture the temperature should be kept stable in the production process.5 The effects of different hunger to the internecine situation of shrimpThe research set five treatments, are the hunger group, satiation group shrimp, satiation with copepods group,66% satiation copepods group,33% satiation copepods group, and the remaining conditions are the same, to observe and record the internecine situation of different groups.There is on internecine situation in formula food and copepods satiation groups; there is approximately 5% death because of internecine situation in 33% satiation copepods group and 66% satiation group; about 27% death because of internecine situation was found in the hunger group.The results showed that:internecine situation wouldn’t happened when the bait is enough, in the absence of food, the internecine situation will be happened frequently, I suggested use a separate feeding strategies to ensure adequate food while most shrimps were molted, which may be helpful to increase survival rate. |
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