Expressible fluid was obtained from fillets on the 1st, 4th, and 14th days of refrigeration. The protein concentration was determined and electrophoresis using cellulose polyacetate strips was performed on each sample. The protein concentration remained constant between 6 and 8 g/100 ml over the 2-week period. Qualitative and quantitative examination of the densitometry tracings revealed that protein(s) having specific migratory characteristics were strongly associated with the duration of storage at 2 C.