マイクロデータロガーによるイナダの遊泳行動解析

抄録

An acoustic transmitter and two micro data recording tags were used to observe the behavior of yellowtails Seriola quinqueradiata, in Sagami Bay, Japan from 24 October through 19 November. Depth data were continuously recorded for 23 days and temperature data for 27 days with a 20-minute interval. The yellowtails showed an apparent diurnal vertical migration pattern in their movements; they crossed the thermocline actively during the daylight hours, but calmed down and remained in the shallow layer above the thermocline at night. Their movements were changed by environmental temperature variation: 1) After the ambient water temperature rapidly decreased, a change was seen in the average depth and pattern in the vertical movement of the yellowtail. 2) They could move vertically to avoid the warm water from the Kuroshio because no ambient temperature rise and no shallower position were observed when the warm water intruded into the bay from the Kuroshio.