Abstract:Salinity has significant influences on the growth, metabolism and physiological changes in fish. In this study we explored the growth of juvenile Eleutheronema tetradactylum (7.82±0.43 g) and the Na+/K+-ATP enzyme under five graduated salinities, and found that salinities had impact on the growth and survival of the juvenile fish. We tested the growth performance under salinities of 2, 10, 18, 26 and 34. Along with the increase in the salinity, the final weights, SGR, DWG, GBW and GBL of the juvenile fish all decreased, and there were significant differences (P<0.05) between some salinity groups. Salinity 2 had the highest values of all measurements, and it was significantly different from salinity 18, 26 and 34 (P<0.05), but there was no difference between salinity 2 and salinity 10 (P>0.05). The measurements of salinity 34 were significantly lower than other groups (P<0.05). The feed coefficient of juvenile fish increased as the salinity rose, and some groups showed significant differences (P<0.05). The survival rate of salinity 34 is 72.2%, lower than other groups (P<0.05) of which the survival rates were above 90%. Salinity also affected the Na+/K+-ATP enzyme in the gill of juvenile fish. After 3-day salinity domestication, the activity of Na+/K+-ATP enzyme in some groups was remarkably increased. The enzyme activity at salinity 34 was significantly higher than other groups (P<0.05), and salinity 18 and salinity 26 exhibited lower enzyme activities (P<0.05). After 10 days the enzyme activities at salinity 2, 10 and 34 became slightly lower, and thereafter all salinity groups displayed stable enzyme activities. After a 30-day culture, we found that the optimal salinity for Na+/K+-ATP enzyme was 34 at which the enzyme activity was significantly higher (P<0.05). The enzyme activity at salinity 2 and 10 was insignificantly lower than that at salinity 18 and 26. These results demonstrated that salinity had effects on the growth of juvenile E. tetradactylum and its Na+/K+-ATP enzyme activity.
