6. At the same time it has been postulated that the catch rates are proportional to 

 the density of distribution of these fishes and the distributions and migrations of the fishes have 

 been considered on this basis. 



7. In this manner some information has been gained, but unfortunately, because of 

 the great unevenness in the seasonal and geographical distribution of the data, it has been im- 

 possible to arrive at as satisfying a conclusion as was hoped for at first. 



8. However, in some sea areas data are fairly abundant and it can be thought they 

 will have some value and significance as basic information for production plans. 



9. When we consider the distribution and migration of these fishes on the basis of 

 their catch rates, the ordinary pattern which we find is for a plot of the curve of catch rates by 

 months in a given sea area to have two peaks and two low points in the year, one pair in the 

 summer and one pair in the winter. The catch rates go from their maximum to their minimum 

 in about half a year. Consequently It is thought that there is a 1-year cycle in the movements of 

 the schools. 



10. As was just stated, two peziks in the catch rates in I year can be detected, but 

 they appear to differ somewhat in character. It is believed that usually the peak which appears 

 in the summer is made up of so-called "ascending fish" and that appearing in the winter is made 

 up of the so-called "descending fish". 



11. These two types of migration appear in some species to be divided into spawning 

 migrations and food-seeking migrations. In the cases which are thought to be of the spawning 

 migration type, dense schools appear over a rather broad sea area in am extremely short period 

 of time and then disappear with equal rapidity so that it is difficult to follow the paths of their 

 migrations. In the cases which are thought to represent food-seeking migrations, the schools 

 appear to congregate gradually in a comparatively limited area, the movements of the schools 

 are comparatively slow, and the paths of migration can be determined quite clearly. 



12. Under present conditions the matters discussed in the preceding paragraph are 

 still completely within the realm of hypothesis. They must be clarified in the future by tagging 

 experiments, fish catch statistics, and biological studies, but they are believed to have an 

 importcint significance both from the point of view of the commercial fishery atnd from the point 

 of view of population studies. 



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