+-ATPase activitiessurvival rates and serum ions of 7-month-old juvenile Russia sturgeon 48 h and 96 h after transfer to freshwater and salinity levels of 525. Fish were also acclimated in brackish water for 2 weeks. The 96 h death rates in salinities 15100% and 100% respectivelyand no mortality occurred in lower salinity groups and control group . The changes on serum osmolalityin salinity groups ， within 96 hours showed a similar trend. All these indicators elevated with the rising salinities and were significantly higher than those in control ）. The indicators in salinity 15 were the highest and there were no significant difference between salinity 5 and 10 groups ）concentration in salinity groups decreased at first in 48 hours and then slightly increased between 48 h and 96 hbut they were all significantly lower than the control group within 96 h period），（）-ATPase activities in salinity groups also showed a firstly decreasing and then increasing trend during the experimental periodand they were all the lowest at 48 h and significantly lower than those in control ）-ATPase activity in salinities 5 and 10 showed no significant difference from the control group and each other ），-ATPase activity in salinity 15 was significantly different from the lower salinity groups and control group ）and corresponded to salinity 10.02. The 96 h isoionic points for serum Na^{were estimated as 146.1 and 136.8 mmol·Lwhich corresponded to the salinities 9.02 and 8.95 respectively. As compared to salinity 15 groupsalinities 5 and 10 groups showed a minor deviation from the control group in all measurement indicatorswhich in salinity 10 after 15 d exposure also showed a minor change from the control group，we can draw a conclusion that 7-month-old Russia sturgeon possess regulatory mechanisms capable of maintaining considerable control of serum ion concentrations in salinity below 10 but unable to survive salinity exceeding 10.}