The effects of various salinities and fresh water (FW) (0.4 ppt) on the growth performance, body traits and fillet composition of juvenile and young sea bass (Dicentrarchus labrax) in FW were investigated in two separate experiments in this study. In Experiment 1, following acclimation, sea bass juveniles (9.5 ± 0.5 g) were reared in 240-L fibreglass tanks (40 x 40 x 150 cm) for 90 days in five different treatments (FW, 10, 20, 30 and 40 ppt). The fish cultured in FW, 10 and 20 ppt grew better than those at 30 or 40 ppt (P 0.05). Yet, the dry weight of the fish grown in FW was significantly lower than those reared in saline waters (P 0.05). Fish growth rates were 0.72 g day-1 in SW and 0.81 g day-1 in FW. Salinity did not significantly affect the meat crude protein, lipid or ash content (P > 0.05). Food conversion efficiency (FCE) was slightly higher in SW (77%) than in FW (74%). The mean fillet weight of the fish reared in FW was 16% higher than for SW. Fillet yields in FW and SW were 52% and 50%, respectively. From the blood plasma ions, Na+ and Cl- were lower in the fish grown in FW as compared to SW (P 0.05). Yet, the dry weight of the fish grown in FW was significantly lower than those reared in saline waters (P 0.05). Fish growth rates were 0.72 g day-1 in SW and 0.81 g day-1 in FW. Salinity did not significantly affect the meat crude protein, lipid or ash content (P > 0.05). Food conversion efficiency (FCE) was slightly higher in SW (77%) than in FW (74%). The mean fillet weight of the fish reared in FW was 16% higher than for SW. Fillet yields in FW and SW were 52% and 50%, respectively. From the blood plasma ions, Na+ and Cl- were lower in the fish grown in FW as compared to SW (P < 0.05), but K+ level did not vary between the treatments
