Effects Of Salinity On Growth, Survival Rate Of Ten Families And Reproduciton Of Litopenaeus Vannamei

Litopenaeus vannamei has a good cultivation speed since it has been brought intoour country.As it has a good compaitbility,a strong disease resistance,and growthquickly.At prQSQnt,Z//o/?e/7aeus vannameibeen became the major cultivation varietyin coast and interior include fresh water area of China. Accompanied by certain keytechnological breakthroughs, especially artiifcial breeding, the Litopenaeus vannameifarming industry developed rapidly, and it became one of the most abundant species inChina.This experiment was conducted to investigate the effects of different salinities onthe growth, survival rates, sexual development, spawning, fertilization rates andhatching rate in shrimp Litopenaeus vannamei from low-salinity water.1.Preliminary studies on broodstock maturation of Litopenaeus vannamei fromlow-salinity water farming ponds were carried out in the laboratory. The prawns werereared under different salinities of1,8,15,23,and30respectively. Unilateral eyestalk offemales were sheared to promote maturation, the water temperature of male shrimpcontrol at (27±0.5)°C, the female shrimp to control the water temperature at (28土0.5)°C.The sexual development, spawning, fertilization rates and hatching rates of thoseparents were investigated. The results showed that gonads of females can mature in theifve salinity conditions; The proportion of mature females was10%in salinity1，70%in salinity8and15with low fertilization and no nauplius? more than76%in salinity23and30with low hatching rates.Histological observation showed that the ovariandevelopments were not different in8?30salinity conditions. The gonads of males couldalso mature normally，but the speed of sexual development in salinity23and30wassigniifcantly faster than in salinity15and8. As salinity lowed, male shrimps neededmore time for maturation. The spermatophore in all the salinities after transplantationcan be fertilized and hatched nauplius.This study conifrmed that Litopenaeus Vannameireared in low salinity can be domesticated and breeding when the salinity more than23.2.Preliminary studies on broodstock maturation of Litopenaeus vannamei from low-salinity water farming ponds were carried out in the laboratory. After all shrimpwere salinization to30salinity，the three experimental groups were breeding lOd,20d，30d respectively before eyestalk-ablation.The results showed that the fertilization rate ofthe three experimental group were84.22士0.033%，83.14士0.026%and82.69士0.043%，and the hatching rate reached35.58士0.091%，40.19士0.092%and34.04士0.117%respectively; The percent of normal sperm count of shrimp were more then93.28士0.89%in all groups. There were no significant differences (P>0.05) in gonadaldevelopment, fecundity, males spermatophore development, fertilization rate andhatching rate.3. The experiment was conducted to determine effects of different salinities (1，15，30,) on growth raets and survival raets of ten families of Litopenaeus vannamei. Theresults suggested that salinity has different effects on the ten families.The weight gainrate and speciifc growth rate of all families were lowest in30%o salinity. The weightgain rate and speciifc growth rate of family J7were highest in15%o salinity group andthe highest rate of weight gain rate and speciifc growth rate of remaining nine family in1salinity group. The growth of family J10was the highest in all salinity group. Theweight gain rate were604.52，604.52and582.25respectively with speciifc growth ratewere3.90,3.84and3.65respectively in1%。，15%o，30%o. The survival rate of family J2reared in l%o salinity was higher than those reared in higher salinity and the survivalrates of remaining nine family were higher reared in15%o and30%o salinity. With theextension of time, the survival rates of all families except J2reared in l%o salinitydecreased rapidly，until the end of experiment, the survival rates of nine family rearedin l%o salinity were far lower than the high salinity group except for family J2.