The Shoreward Migration of Japanese King Crabs at a Fishing Ground in Western Kamtchatka

概要

論文の詳細を見る
Set-net catches of Japanese King Crabs in Voroskaya fishing ground, from mid-June to late-August 1934, were examined. The whole area was arbitrarily divided into the successive sub-areas, each including several nets, all of which were set in parallel rows at almost uniform intervals parallel to the coastal line. 1. In an assigned sub-area, it was assumed that the cubs had migrated toward or off from the shore in accordance with the catch of a net, whether it was larger or smaller than that of another net, situated on the shoreward side of the first net; provided that the whole course of a continuous plying of the net of larger catch was covered by that of another net, only such pairs of nets out of all in the sub-area having been chosen. The constant ratio found between the catches of both nets of such a pair (Fig. 2) supports the assumption. 2. Further, with the net of larger catch, the catches per unit area of net were compared on the right and left halves of the net, and the larger side was assumed to indicate the main path of migration. 3.The composition of the group of crabs caught shows a difference before and after the mid-July (Table 1). A group seems to have migrated shoreward in early June (Fig. 1, a) and left the ground in early July (Fig. 1, b), while another group seems to have come and left the ground during the last fishing season (Fig. 1, c).