We had inadvertently observed an ordinary muscle of cultured red sea bream, Pagrus major, to give an abnormally high 2-thiobarbituric acid (TBA) value. In order to evaluate the extent of lipid peroxidation in cultured fish tissues, we investigated the relationship of ordinary muscle and liver TBA values of 3-year-old cultured red sea breams with their dietary α-tocopherol and lipid levels, including the comparison of the cultured fish and wild red sea breams. The α-tocopherol contents of both tissues from the cultured fish were positively correlated with those of their diets and negatively correlated with the respective tissue TBA values. Thus, a depletion of α-tocopherol from the diets resulted in accelerating lipid peroxidation in the cultured fish tissues with the remarkable effect especially in the case of the ordinary muscle. In addition, the
cultured fish muscle gave an abnormally high TBA value as compared with the wild fish, although their α-tocopherol contents were not significantly different from each other. The results obtained suggested that the cultured fish muscle may be more susceptible to lipid peroxidation than the wild fish and that the dietary α-tocopherol of the cultured fish plays an important role to protect the ordinary muscle against lipid peroxidation.