Shelf life of cultured sea bass packaged in air, vacuum, and gas mixture packages stored for 40 days at $2.90{pm}0.02^{circ}C$ was compared. The gas mixtures used contained $CO_2$, $O_2$, and $N_2$ at difference percentages (M1: 75% $CO_2/25%$ $N_2$; M2: 60% $CO_2/40%$ $N_2$; M3: 30% $O_2/30%$ $CO_2/40%$ $N_2$). Sensory and physical parameters, chemical changes, and microbiological counts were monitored during storage. Storage with a gas mix including 75 and 60% $CO_2$ was more effective than vacuum processing and packaging with a gas mix that included oxygen. Vacuum was the most effective method for preventing lipid oxidation. The optimum method for sea bass in view of all analysis results was modified atmosphere packaging (MAP) and the most suitable gas mix ratio was 75% $CO_2/25%$ $N_2$. The best days for consumption of sea bass packaged with air, MAP (M1, M2, and M3), and vacuum were $4^{th}$, $28^{th}$, $28^{th}$, $16^{th}$, and $20^{th}$ days, respectively.