抄録
It is believed that scale pattern of fish, it's otolithes, backbones and so on contain ecological informaton representing such as the the rate of growth, physiological state of fish, the river stocks and others. The scale pattern characters have, thus, been utilized for the determination of the fish age and the river stock to presume the amount of such marine resources as salmons captured in the ocean. At present, however, the measurement of these scale pattern data is performed by means of visual and manual methods by the professional specialists. In the present paper, reported is a new method for estimating the age of chum salmon using its scale pattern data optically read.
A scale of chum salmon is a small object having a diameter of approximately five milimeters. The center of the scale pattern is referred as a “focus”, and annual rings like those found in the stump of a tree are observed surouding the focus. In the scale pattern, the two kind of belting zone of rings are seen, one of which is referred as “resting zone(or winter zone)” and the other “growth zone(or summer zone)”. The former is the part in which the crculus interval is narrow, showing the growth rate is very slow, and the latter the part in which the interval is wide, indicating the favourable growth of of scale compared with resting zone.
The number of the resting zone is regarded equal to the age of the fish. The authors developed and propose a new mathematical function, which may be defined as “Tendency Density Function” by which the number of the resting zone can easily be extaracted and measured. The parameters to be measured are the number of circuli, (N), and the intervals between circulus, (Xi), in milimeters along the line drawn outward from the focus of the circuli pattern.
In the present analysis, the circulus and intevals data on each of ten lines for one sample were measured so that the data obtained might represent the information being involved over the entire plane of scale pattern. From this point of view, the authors designated these as the “two dimensional data”.
Conclusion;
The results of the age determination by the above mentioned means are as follows; The ages measured by the proposed method coincided with those measured by the visual method on approximately ninety (90) percent of the sampled fish. It was demonstrated that the proposed “Tendancy Density Function” was extremely useful for the purpose of estimating the fish age from the scale pattern information.
