ベーリング海東部における底曳網漁場の研究-I

Abstract

In the previous paper, it was shown that the movements of yellow-fin sole, Limanda aspera (PALLAS), is related to the change of bottom temperature on the trawl fishing ground in the eastern Bering Sea, 1960. In this paper, the authors compare the oceanographical conditions in 1963 with 1960, and they report on the distribution of yellow-fin sole and alaska pollack, Theragra chalco-gramma (PALLAS), in 1963. The results are as follows: 1. The sea water temperature on the bottom in the central portion of cold water mass in 1963 was 1°C higher than in 1960. The isothermal-line of 0°C in the cold water mass extended from south-east of St. Matthew Island to 57°N, 164°W in 1960, but in 1963 it was found to exist only in the south eastern part of the island. 2. The open sea water of high salinity reached from the southern part of Bristol Bay across the bay to the north-side of the cold water mass in 1960, but in 1963 it was found only in the southern part of the bay. 3. Yellow-fin soles were distributed in a large number on the north-side of the cold water mass, limited to only a few at the center and none in the southside in July, 1963. 4. Between April and June, the shoals of yellow-fin sole moved from the north-western part of Unimak Island to the shallow coast of Bristol Bay. In July, the shoals moved toward off-shore region with the rise of bottom temperature in the shallow region and then migrated northwestward across the region (around 57°30'N, 163°W). At the both fronts of cold water and coastal water increased the density of the shoals more in the region above mentioned. 5. Alaska pollacks were distributed in a large number on both the east and south-sides of the cold water mass, and none on the north-side in July, 1963, because they are controled by open sea water with high temperature and high salinity. 6. The stomachs of alaska pollack contained aboundant Thysanoessa raschii and Parathe-misto libellula which were living near the surface of the water. The distribution of this fish proved to have relations not only to the bottom water con-ditions but also to the water conditions at different levels.