The morphological features of a super swarm of krill, Euphausia superba

概要

論文の詳細を見る
During the R. V. MELVILLE (USA) Cruise in 1981,a dense aggregation of krill near the Elephant Island was mapped acoustically. The data acquisition system consisted of a Braincon fin equipped with 2 downward oriented transducers operating on 50kHz and 120kHz, respectively. The signals were recorded on F-M seven track taperecorder and integrated with one minute intervals and by 10m depth strata down to at 190-200m depth. The results were expressed in dB/m^3 or dB/m^2 surface area. In general the edges of the aggregation appeared well defined with a steeper gradient on the exposed than on the lee side. The vertical distribution at the edges presented a wedge or lens shaped picture which usually was located in 30-40m in depth but could also be found toward the bottom. In the central part density was uniformly high from 30m and down to 140-150m depth. The structures were constantly shifting with deformation and reformation obviously related to the ongoing vital processes of the individual krill. Some differences were noted in the results derived by the two frequencies 120kHz and 50kHz.
国立極地研究所の論文