Genotype By Environment Interaction Of Harvest Boby Weight Of Pacific White Shrimp(Litopenaeus Vannamei)Cultured In Normal Salinity And Low Salinity

The pacific white shrimp(Litopenaeus vannamei)has the advantages of high meat content,high resistance,fast growth and high density breeding,and it is one of the three kinds of world shrimp farming.The pacific white shrimp(Litopenaeus vannamei)enable to culture under low salinity condition by the process of desalination for juvenile of Litopenaeus vannamei,on account of the high tolerance to salinity,and it has became an important breeding mode.With the expansion of the scale of farming,production in low salinity condition increased year by year.In recent,the culture model of low salinity for Litopenaeus vannamei has been developed rapidly in the United States,Thailand,China,and other countries.However,the water quality was affected easily by climate,components of planktons,and the big difference temperature between day and night,and it was complex,variety,unstable,which directly or indirectly affects the growth and survival of Litopenaeus vannamei,in the process of intensification culture under low salinity.Therefore,this paper has carried out mainly work of selection breeding for the culture of low salinity for Litopenaeus vannamei,and established a great number of families of Litopenaeus vannamei,and gradually desalinated these families,and then conducted polyculture test.Estimated genetic parameters for survival of Juvenile families of Litopenaeus vannamei during desalination and culture Stage;analyzed genotype by environment interaction of harvest body weight of pacific white shrimp(Litopenaeus Vannamei)cultured in normal salinity and low salinity;compared body weight and survival rate of Litopenaeus vannamei reared in normal and low salinity.The results were as follows: 1.Genetic parameters for survival of juvenile families of Litopenaeus vannamei during desalination and culture stageIn 2015,a total of 15000 individuals from 100 families of Litopenaeus vannamei were desalinated and reared at a low salinity of 5‰ in the juvenile stage.Survival rate of families were compared for desalination and culture stages and the heritability estimates of survival were estimated.The results showed that the range of survival rate for two stages were 19.33-100.00% and 11.9-99.2%,and the average survival rate were 66.7% and 67.5%,respectively.The range of overall survival rate for the juvenile stage was 6.67%-90.67%,and the average survival rate was 46.91%.Statistical analysis showed that there were significant differences on survival rate between families for two stages(P<0.01).There was a significant and moderate positive correlation on survival rate of families between two stages(r=0.61,P<0.01).The heritability estimates of survival for two stages were obtained by the model including the additive genetic effect(A)and the model including A and the common environmental effect(C).With A model,heritability estimates of survival for the desalination,culture and combined stages were 0.09,0.10 and 0.14,respectively,and were significantly different from zero(Z>2.58).Based on A+C model,heritability of survival were 0.06,0.05 and 0.07,respectively,and were not significantly different from zero(Z<1.96).The genetic correlation on survival rate of families between two stages for Aand A+Cmodels were 0.41±0.09 and 0.48±0.09,respectively.2.Genotype by environment interaction of harvest body weight of pacific white shrimp(Litopenaeus Vannamei)cultured in normal salinity and low salinityIn 2016,78 families of normal salinity and 79 families of low salinity were cultured in a common pond,respectively,analyzed genotype by environment interaction of harvest body weight of pacific white shrimp(Litopenaeus Vannamei)cultured in normal salinity and low salinity.The results showed that there was significant differences between normal salinity and low salinity for harvest body weight(P<0.01)and survival rate(P<0.05)by general linear model.The heritability estimates for harvest body weight of normal salinity and low salinity were 0.674±0.089 ? 0.329±0.070,both belong to high level heritability,and were significantly different from zero(P<0.01).And the heritability estimates for harvest body weight between two environment was significant difference(P<0.01)by Z-score test.The genetic correlation between normal salinity and low salinity for harvest body weight was 0.496±0.128,belongs to moderate positive correlation(0.30<R<0.50),and was significantly different from one(P<0.01).The value of K was 0.87,this implied that there was high genotype by environment interaction effect between the two environment for harvest body weight(K>0.5).3.Comparison body weight and survival rate of Litopenaeus vannamei cultured in normal and low salinityIn 2015,85 families of normal salinity,89 families of low salinity were mixed a common pond respectively.Compared body weight and survival rate of Litopenaeus vannamei reared in normal and low salinity.The results showed that,the average harvest weight of normal salinity(13.20g)was significantly higher than that of lowsalinity(7.91g)(P<0.01),and the average survival rate(0.65)was significantly higher than that of lowsalinity(0.45)(P<0.01).The range of mean weight of families for normal salinity was 9.14-19.37 g,the range of lowsalinity was 5.06-10.70 g,the difference between normal salinity and lowsalinity of harvest weight was significant(P<0.01).The survival rate of families of normal salinity and lowsalinity was 0.29-0.95 and 0.08-0.83,respectively,the survival rate of normal salinity and lowsalinity was significantly different(P<0.01).The body weight growth rate and specific growth rate of normal salinity was 0.115±0.032g/d and1.424±0.055%,respectively,and lowsalinity was 0.080±0.019g/d and 1.605±045%,respectively.There was significant difference between families of normal salinity and lowsalinity for the body weight growth rate and specific growth rate(P<0.01).