Effect of salinity on carrying capacity of a recirculation system for Nile tilapia, Oreochromis niloticus L.; production was assessed. Survival, growth and feed conversion ratio of adult Nile tilapia fed 30% crude protein diet for 88 days were measured at three di¡erent salinity levels (8,15 and 25 g L-1) and two stocking densities (20 and 40m-3) in three independent recirculating systems.