Introduction: The aim of this study was direct transfer of four species of newly sturgeon (Huso huso, Acipenser persicus, Acipenser gueldenstaedti and Acipenser nudiventris) obtained from artificial reproduction to the Caspian Sea water.
Materials & Methods: The fish in four different age groups (35, 50 and 65 days) and in three different saline water (FW: <0.5%, EW: 9.5%, and CSW: 12.5%) were investigated. The fish were transferred directly from fresh water to brackish water. After 168 hours,
blood samples were taken from the fish.
Result: The results showed that the survival in all groups was from 65 to 100% and increased with increasing age and weight of fish. Some blood parameters, cortisol level, osmolarity and plasma ion concentration were determined. The functional levels of the mechanism of osmotic and ionic homeostasis were similar in all groups (P>0.05) but differed in experimental media (P<0.05). Significant differences were observed between the levels of plasma ion concentrations in different media (P<0.05). Plasma Na+, K+ and
Ca+2 concentrations were higher than those of FW media, but lower than in Brackish water media (P<0.05). Plasma Mg+2 concentrations were lower than those of FW and Brackish water media (P<0.05). The Hct, Hb, MCV, MCH and plasma osmolarity decreased and MCHC and plasma cortisol levels increased with increasing salinity (P<0.05). But the number of WBC and RBC did not change (P<0.05) and reached a stable state.
Conclusion: As a result, it is possible to release newly sturgeon directly from fresh water to brackish water with increasing weight and age.