瀬戸内海におけるイワシの漁況について
(第1報)漁獲高の永年變化
1950 年 16 巻 4 号 p. 132-136
詳細
1950 年 16 巻 4 号 p. 132-136
The secular variation in the yield of “IWASI” in the Inland-Sea which fails to be separated into those of Sardine, Anchovy and Round-Herring from the past records, is classified into three types by testing it statistically as time series. A most significant characteristic of the type 1, represented by those from Osaka, Okayama, Hirosima, Kagawa and Tokusima Prefectures which face the Inland-Sea only, is found in the gradual increase of the yield. On the type 2, represented by the fish caught in Hyogo, Wakayama, Yamaguti and Oita which open both in the Inland-Sea and the open sea, this yield has been shown to have declined greatly. And also on the type 3, represented by Ehime, the yield increased first but has been decreasing since 1935. The yearly decreasing stock of Sardine and the increase in intensity of fishery are of importance in explaining fluctuations in the yield, and, what is more important, it is by the different mixing ratios among the three kinds of “IWASP” migrating to each prefecture that three types are chiefly determined in the secular variation.
