Life stages and seasonal variances of salinity tolerance of Triplophysa yarkandensis (Day，1877) in Tarim River

In order to explore the influence of increased salinization on fish populations in Tarim River, sodium chloride (NaCl) salinity tolerance in T. yarkandensis (a native fish species), was measured in laboratory by applying slow acclimation (SA, gradual salinity increase) and direct transfer (DT) methods in spring season. Whereas Probit method was used to calculate the median lethal concentration (LC50). Results of slow acclimation for adult, juvenile and larva fish (LC50) showed 16.51 g/L, 12.94 g/L and 8.13 g/L[cy1] , respectively. Results of salinity tolerance (LC50) by DT method, were recorded as 16.16 g/L, 11.01 g/L, and 7.37 g/L for adult, juvenile and larva, respectively. The salinity tolerance of the fish showed age-dependent increasing tendency. The experiments have also been conducted in three other seasons to study the relationship between salinity tolerance of adults and seasonal salinity variances in Tarim River. Results showed a significant S relationship between river’s salinity and the LC50 of adults (data mixed the SA and DT) by using equations y=e2.788-0.121/X (R2=0.994, P=0.003) for DT, and y=e2.771-0.120/X (R2=0.927,P=0.037) for SA. These findings suggest that T. yarkandensis has a physiological adaptation for osmoregulation in developmental processes and in dealing with the seasonal salinity variances of the Tarim River.