Relation Between the Age of Shark and the Group Accumulative Ratio of Vitamin A

Abstract

Accumulation of vitamin A-the growth promoting vitamin-in the liver is very little in early stage of growth, while it will suddenly be accumulated in the liver of the shark when it has grown to adult (above 80cm in body-length) (Fig. 1).
The ratio of vitamin A concentration above 10 C. L. O. U. to whole individuals in each body-length-may be called the group accumulative ratio of vitamin A-were calculated and were graphically shown in Table 1 and Fig. 2.
The estimation of the age of shark will be depended only on the body-length, because shark has no annual rings on scales or ear stones.
The author has made the deduction of the age of a shark (Squalus suckleyi) from the frequency curves of the body-length by using the samples of the ONAHAMA, the NIPPON-KAI and the HOKKAIDO-TOHOKU Sea region, surrounding Japan Islands (Fig. 3). From the results of these treatments, it was presumed that the shark grows about 15-25cm a year. The re-lation of age and body-length as being shown in Table 2. At two age it reaches the economical minimum body-length (60-70cm), while the first parturition age is attained at three age (85-95cm in females and 65-70cm in males).
It may, therefore be, said that the group accumulative ratio of vitamin A in the shark is rapicl1y increased at three age in which the gonads have been ripened both males and females.