Abstract
Acoustic telemetry was used to monitor the behaviour of hatchery-reared Pagrus major individuals, which have limited locomotion, to determine whether they can remain at release sites under high-current conditions. Eight fish (four 0+ year and four yearling fish) were released in the Kagoshima Bay after surgically attaching acoustic transmitters. The results showed that the yearling fish clearly exhibited diurnal behaviour. However, the 0+ year fish exhibited a 12-h behavioural cycle that was related to the tidal cycle. The results of the statistical model analysing the explanatory variables, diel movement, sea level, and tidal range were selected using an information criteria, suggesting that the occurrence of the yearling fish was related to diel movement, but the occurrence of the 0+ year fish was related to tidal range and sea level. The results imply that the 0+ year fish migrate from the research area or hide in fish aggregating devices (FADs) under prevailing tidal current conditions. It is important to consider the timing of release for small reared fish. Two tagged fish returned to the study area near the FADs after moving out of the detection zone. Thus, it seems that the FADs might play an important role in attracting the released fish, as indicated by the results of the current study.
