Seasonal variations in major biochemical components (water, lipids, protein, and ash) in the muscle and liver of bib, T. luscus L. were followed using samples of fish taken from commercial catches from November 1987 to October 1988. Analysis of variance (ANOVA) showed that there were significant differences between sexes and between months for all the components considered. Therefore, males and females were studied separately in subsequent analysis. Water content of muscle and liver increased during spring, reached the highest values in April and fell gradually in summer. Protein levels remained fairly constant with slight increases occurring during winter and a decline in March, reaching minimum values in April. Seasonal changes in liver lipid content followed virtually the opposite pattern of that of the liver water content. Thus, lipid content of the liver decreased through the spring coinciding with the spawning season and reaching minimum values in April. A recovery of liver lipids was observed in May. It is concluded that the main source of lipid for gonadal development in this species is the liver reserves.