Effect of Sudden and Gradual Transfer of Oreochromis aureus to Different Water Salinities on the Activity of AST and ALT Serum Enzymes

The effects of Sudden and Gradual salinities stress on AST and ALT enzyme activity inOreochromis aureus fingerlings were investigated in two separate experiments in this study. Thefingerlings were suddenly transferred to five different set of salinities (5, 15, 25, 35, 45 psu) andgradually each one hour to seven set of salinities (5, 10, 15, 20, 25, 30, 35) psu in two replicatefor each salinity for 72 hrs. Fish were killed after that and blood were taken from heart and puttedin test tubes for serum separation and serum kept in freeze until doing measurements of AST andALT enzymes. Results showed that all fishes were died in the salinity concentration 45 psu after20 hrs of sudden transfer, while a 100% survival rate was recorded in other salinityconcentrations. The salinity 45 psu was considered to be out of the O. aureus tolerance range.Findings showed a close correlation of AST and ALT concentrations with salinity increase insudden and gradual transfer experiments as a result of the stress which occurred during fishacclimation to reach the homeostasis. The remarkable increase in serum ALT and AST of fishgroups exposed to sudden transfer compared with gradual transfer groups reflect the better abilityof these fishes to adapt in salinity changes of gradual transfer..