title: Effects of gradual salinity increase on osmoregulation in Caspian roach Rutilus caspicus.
abstract: This study was carried out to determine the effects of gradual salinity increase on osmoregulatory ability of the Caspian roach Rutilus caspicus, under conditions which mimic stocking conditions of hatchery-raised fish. Initially, 30 juvenile fish (mean ± S.D. 3.20 ± 0.34 g) were transferred to 20 l circular tanks, in which salinities were changed in a stepwise fashion, from 0 to 5, 10 or 15 at 48 h intervals. The fish at salinity 15 were held for an additional 48 h at this salinity. Forty-eight hours after salinity transfer, survival rate, haematocrit, plasma Cl(-) , Na(+) and K(+) concentrations, osmolality and gill Na(+) /K(+) -ATPase (NKA) activity were measured. The only effect of exposure to 5 was a significant reduction in haematocrit compared to the freshwater control group. Exposure to salinity 10 raised haematocrit, Cl(-) and Na(+) concentrations and osmolality. At 48 h exposure to salinity 15, haematocrit, Cl(-) and Na(+) concentrations and osmolality were significantly higher than freshwater controls, and gill NKA activity was significantly lower, but the effect on NKA was no longer evident at 96 h exposure. There were no effects on survival. These results indicate that R. caspicus juveniles experience an initial non-lethal iono-osmotic perturbation following salinity increase but can adapt to brackish water at salinity 15.
authors: Gorgan University of Agricultural Sciences and Natural Resources (GUASNR), College of Fisheries and Environment, Shahid Beheshti Ave, Gorgan 49138-15739, Iran.
authors: S
authors: S
authors: Malakpour Kolbadinezhad
authors: A
authors: A
authors: Hajimoradloo
authors: R
authors: R
authors: Ghorbani
authors: H
authors: H
authors: Joshaghani
authors: J M
authors: JM
authors: Wilson
mesh_terms: D000064:Acclimatization; D000818:Animals; D017756:Aquaculture; D003530:Cyprinidae / Q000502:physiology*; D005618:Fresh Water; D006400:Hematocrit; D054712:Salinity; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase