福井県浦底湾におけるミズクリゲの生熊-X : 1970年夏期における成体型の夜昼移動

概要

論文の詳細を見る
From August 19-20, 1970, the diel vertical migration of Aurelia aurita population during a period of 23 hours was investigated at the outer-western part of Urazoko Bay, Fukui Prefecture. Methods of sampling and environmental analysis were approximately the same as those employed in the previous studies.The results obtained are summarized as follows:1) The medusae collected ranged from 5 to 17cm in bell-diameter and almost all of them were confirmed immature. They were distributed at the bottom layer below 10 meters during the daytime (11:00-15:00) in fine weather. However, about 50 percent of them distinctly swam up at 17:00 to the middle layer about 6 meters deep before sunset. During the dark hours, most of them were collected from the bottom layer. Thereafter, a small percent of medusae migrated to the surface at 5:40 shortly after sunrise the next morning, but the main distribution layer moved to the bottom layer at 9:05, when it was fine.2) Although the most important factor controlling the migration of Aurelia medusae was again confirmed to be underwater illumination, temperature above 30°C seemed to restrict their activity toward the surface layer.3) The sinking or refloating velocity of the medusa was estimated to be around 3 meters/hour.
公益社団法人日本水産学会の論文