北西部太平洋におけるビンナガ鮪漁場動態に関する研究-IV

Abstract

The present discussion dovers important problems of the practice of fisheries, especially in searching the tunas at a deep layer for the long-line operation during the winter season. From available data of long-line fishing the author examined the migrations of albacore community in the waters adjacent to Japan in 1954-55.The results obtained are summarized as follows; (1) Distributions of the albacore community based on the iso-hooked-rate-line during the winter period can be regarded as “fish ranges” because of their resembrance to “mountain ranges” (Fig. 1 and 3). (2) From the figures of the distributions of albacore we know the number of the shoals or the communities, the density, the extent of distributions, the direction of movement of albacore on the southward trip in the winter-spring seasons (Fig. 3). (3) Sometimes there are 18 or 19 shoals migrating in the waters adjacent to Japan, moving southward in parallels (Table 1, Fig. 3). (4) Some shoals migrate westward beyond the Izu Islands, while the others migrate eastward away from the Islands (Fig. 3).