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

Abstract

The effects of Sudden and Gradual salinities stress on AST and ALT enzyme activity in Oreochromis aureus fingerlings were investigated in two separate experiments in this study. The fingerlings were suddenly transferred to five different set of salinities (5, 15, 25, 35, 45 psu) and gradually each one hour to seven set of salinities (5, 10, 15, 20, 25, 30, 35) psu in two replicate for each salinity for 72 hrs. Fish were killed after that and blood were taken from heart and putted in test tubes for serum separation and serum kept in freeze until doing measurements of AST and ALT enzymes. Results showed that all fishes were died in the salinity concentration 45 psu after 20 hrs of sudden transfer, while a 100% survival rate was recorded in other salinity concentrations. 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 in sudden and gradual transfer experiments as a result of the stress which occurred during fish acclimation to reach the homeostasis. The remarkable increase in serum ALT and AST of fish groups exposed to sudden transfer compared with gradual transfer groups reflect the better ability of these fishes to adapt in salinity changes of gradual transfer..