This study was devoted to the identification of specific peptides and proteins which can be used as indicators of freshness in fish. The post mortem evolution of protein patterns in farmed sea bass muscle was monitored by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2-DE) after 0, 2, 4, and 6 days cold storage. SDS-electrophoresis, of total proteins and proteins soluble in low-ionic-strength solutions, revealed the gradual disappearance of a protein band of 16 kDa immediately after fish death. 2-DE allowed the classification of fish samples according to post mortem time. Three spots of interest, which disappeared progressively, were identified on the 2-DE patterns. Further research is required to establish the identity of these polypeptides and to evaluate their expression and post mortem evolution in another fish species.