著者

Noda Takuji Fujioka Ko Fukuda Hiromu Mitamura Hiromichi Arai Nobuaki

出版者

[京都大学フィールド科学教育研究センター]

雑誌

20th Symposium of the International Society on Biotelemetry Proceedings

巻号頁・発行日

pp.17, 2014-05

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19–22 May 2018 Kyoto, JapanOn the cultivation of Pacific blufin tunas Thunnus orientalis in an open sea net cage, it is reported that sudden illumination in nighttime caused by car and fishing light can cause a harmful effect on the fish survival. In this study, behaviour response of schooling juvenile Pacific bluefin tunas (size: 210 - 250 mm) to the sudden illumination change in nighttime was monitored in an open sea net cage (12m x 12m in width, and 6m in depth) by using animal-mounted acceleration/angular velocity data loggers (200 Hz). Two types of illuminator were simulated: car light for 8 fish and fishing underwater light for 11 fish. When the car light was intermittently illuminated over the sea surface for more than 3 min (10 sec on and 10 sec off), the fish significantly increased the max/mean/standard deviation of acceleration and angular velocity with occasional burst, and decreased the similarity in movement cycle. However, no death was observed. The fishing underwater light was turned on and off for 30 sec and 1 min respectively, and the procedure was repeated for 5 times. The fish significantly increased the max/mean/standard deviation of acceleration and angular velocity with more occasional burst than the car light. The responsiveness to the illumination significantly decreased with the repeated times of illumination. One of the fish reached 230.5 m/s_2 in acceleration and 4333 deg/s in angular velocity, and died probably because of the collision to the net wall.

著者

Fujioka K Fukuda H Okamoto S Tei Y Hiraoka Y Takeuchi Y

出版者

[京都大学フィールド科学教育研究センター]

雑誌

20th Symposium of the International Society on Biotelemetry Proceedings

巻号頁・発行日

pp.89-89, 2014-05

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19–22 May 2022 Kyoto, JapanJuvenile Pacific bluefin tuna (Thunnus orientalis, PBF) are still small (about 20cm in fork length, FL) and so weak that even direct touch to the fish can cause fatal damage. Their vulnerability makes it difficult to collect vital data in the natural environment over the past years. We developed an operational instrument for smooth and quick attachment of tags. Fish was kept in the water even during the operation and we shorten the operation time to be 30-60 seconds. Also, the mechanical progress (archival tags downsized dramatically) contributed to the survival rate. The movement patterns of the juvenile PBF was investigated using the archival tags implanted in a fish during August in 2012, 2013 for 75, 62 individuals (18-33cm FL). Twenty one tagged fish were recaptured in total (recovery rate 15.3%), and we downloaded data successfully from eight of thirteen tags recovery. One tagged juvenile, which recorded for 79 days from August to October off Kochi (grew up from 24.5 to 50.0cm in FL). Our data showed that the tagged juvenile moved between coastal areas and offshore into the Kuroshio Current, thus the offshore coverage of their habitat could be restricted to the Kuroshio Current in their nursery areas.