HCO3(-)-ATPase and Ca2+ dependent ATPase activities in the gills of the rainbow trout after the transfer to brackishwater and seawater.

The effect of seawater and brackishwater exposure on gill HCO3(-)-ATPase and Ca2+ dependent ATPase activity in rainbow trout (Oncorhynchus mykiss) was investigated at different periods of time. HCO3(-)-ATPase activity decreased after the transfer to either brackishwater or seawater. Ca2+ dependent ATPase activity decreased during the initial period (1 to 4 days) in both salinities and recovered freshwater values from the 7th day onwards. No effect from fish size was detected in both parameters after saltwater transfer. The results are discussed in terms of salinity and long-term saltwater adaptation.