To clarify the aspect concerning the accumulation and diminution of fat in various parts accompanying the growth of cultured red sea bream, using fish aged 0, 1, and 2, physique and fat contents in muscle parts, visceral parts, hepatopancreas, dorsal white muscle, and the whole body were measured monthly over a year.According to this survey the following results were confirmed.

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SUMMARY: The present study was aimed at a physique index which enabled to evaluate the fat mass in fish body by using the data of standard body length (BL) and body weight (BW) for cultured sea bream at various growth stages. The relationships between BL and BW and between BL and lean body mass weight (LBM) were (BW/BL2.840) × 103 = 52.65 and (LBM/BL2.819) × 103 = 49.74, respectively. Then, we gave a definition to the relationship between BL and BW as (BW/BLα) × 103 = physique index, evaluated the correlation coefficient between the physique index value to several power values of α and fat content in each part of fish body. The α value attained to the maximum level on the correlation coefficient was 2.548 for the muscle part, 2.775 for the visceral part, 2.916 for the dorsal ordinary muscle, and 2.823 for the whole body. The α value of 2.823 in the whole body was closely similar to 2.819 of the α value between BL and LBM. Moreover, the correlation coefficient at 2.823 of the α value gave a significantly high level of P < 0.001, not only in the case of the fat content of the whole body, but also in any case of the muscle part, visceral part, and dorsal ordinary muscle. Therefore, we named this physique index, (BW/BL2.823) × 103, the TM index, and proposed it as an index to reflect the amounts of the whole body fat.

As a part of a study on the improvement of flesh texture in cultured red sea bream, we examined whether body density was useful to estimate the body fat content in live fish.A significant negative correlation was seen between body fat content (BF) and body density (BD) for cultured red sea bream aged one and two years as shown below.BD=-0.0018BF+1.0997 (n=97; p<0.001)The deviation of body density from this regression line, the residual value for each fish, was effected by the muscle ratio in the whole body. These results indicate that body density is useful not only to estimate the body fat content but also to surmise the relative level of muscle ratio in live fish.

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