STUDIES ON FLUCTUATION OF THE VITAMIN A CONTENT IN FISHES-V

Vitamin A was determined on many rainbow trout samples collected on various occasions. Cultured fish showed a greater fluctuation in vitamin A content than the wild fish. Vitamin A in the former ranged from 0.23 to 770 IU per gram of liver and 8 to 800 IU per 100 grams of muscle, while in the latter, from 13 to 430 IU per gram of liver and 23 to 160 IU per 100 grams of muscle. Though some of the cultured fish were rich in vitamin A, the others were found with an extremely low level of the vitamin, namely 144 to 250 IUper kilogram of the body weight, or only one-tenth as low as that of puffers, jack mackerel, etc., which have been known as the poorest fish in vitamin A. Vitamin A in the diet seems to have a great effect on the vitamin A level of rainbow trout, but probably little on the growth of the fish. In many samples, the vitamin A content of the muscle oil changed in proportion to that of the liver oil. The similar tendency was also found in other various kinds of fish in the authors' previous data. Occurrence of some points aberrant from majority of the samples as shown in Fig. 1 may be explicable by a postulation that the liver always precedes muscle in varying its vitamin A level. In other words, a time lag phenomenon in varying the vitamin A level between the liver and muscle may be the cause of scattering of dots in Fig. 1. However, it is likely that vitamin A in the kidney oil changes more proportionally with that in the liver oil than the vitamin in the muscle. Some additional data on the vitamin A in brook trout and landlocked salmon is given in Table 4.