Effect of food deprivation on some physiological responses of Caspian Roach Rutilus caspicus (Yakovlev, 1870) juveniles during acclimation with the Caspian Sea water

This study was conducted to investigate the physiological performance of Caspian roach, Rutilus caspicus juveniles when directly released into the Caspian Sea, taking into account the possibility of their limited access to food for a period of two weeks. A total of 540 fish were randomly placed in tanks in the form of 6 experimental treatments (each with 3 repetitions) including: Group 1: Abrupt salinity increase and feeding throughout the experimental period (Ab.F); Group 2: Abrupt salinity increase and starvation (Ab.S); Group 3: Gradual salinity increase and feeding (Gr.F); Group 4: Gradual salinity increase and starvation (Gr.S); Group 5: Maintained in freshwater (control treatment) and feeding (C.F); and Group 6: Maintained in freshwater (control treatment) and starvation (C.S). The mortality rate of the juveniles and physicochemical parameters of the water were recorded daily throughout the entire experimental period. Osmolality, sodium, potassium, chloride, total protein, cholesterol, triglycerides, glucose, and liver enzymes (ALP, ALT, and AST) were measured in the fish after 14 days. Based on the obtained results, the levels of protein, cholesterol, and triglycerides in the fed fish did not exhibit significant alterations during the transfer to brackish water. However, two-week food deprivation led to a decrease in their levels. On the other hand, the increase in osmolality and sodium, chloride, and potassium in Caspian roach juveniles were only affected by the salinity increase and had no effect on their levels due to food deprivation. Therefore, the Caspian Sea bream (1-2 g) have the ability to adapt to the brackish water of the Caspian Sea and are easily resistant to the conditions of lack of access to suitable food in the new aquatic environment for two weeks.