Vol. 57, 2018 (update: 2018.05.03; 06.04) Tracking Anguilla japonica Silver Eels Along the West Marina Ridge Using Pop-up Archival Transmitting TagsTakatoshi Higuchi1, Shun Watanabe2,*, Ryotaro Manabe3, Tsuyoshi Kaku4, Akihiro Okamura5, Yoshiaki Yamada5, Michael J. Miller4, and Katsumi Tsukamoto4 doi:10.6620/ZS.2018.57-24
1Graduate
School of Bioresource Sciences, Nihon University, 1866 Kameino,
Fujisawa, Kanagawa 252-0880, Japan. E-mail: nagoya_g10@yahoo.co.jp (Received 4 January 2018; Accepted 19 April
2018; Communicated by Hin-Kiu Mok) Takatoshi
Higuchi, Shun Watanabe, Ryotaro Manabe, Tsuyoshi Kaku, Akihiro Okamura,
Yoshiaki Yamada, Michael J. Miller, and Katsumi Tsukamoto (2018) Japanese
eels Anguilla japonica were tagged in order to understand their
behavior in their spawning area. Three silver eels (EEL-A, B, C: TL792,
898, 992 mm) were tagged with pop-up satellite archival transmitting
tags (PSATs) and released at different locations near/in their spawning
area along the southern part of the West Mariana Ridge. EEL-A showed
premature tag pop-up with mostly disordered records and the EEL-C tag
did not pop up, while EEL-B showed stable diel vertical migrations
during 31 of the 43 days it was tracked. EEL-B swam in shallower layers
(411-182 m) during nighttime and deeper layers (563-885 m) during
daytime. The mean nighttime swimming depth ± SD of EEL-B was
significantly deeper during the full moon (342.4 ± 6.8 m) than the new
moon (274.8 ± 16.9 m) and was positively correlated with the moon’s
altitude. EEL-B reached its maximum depths (851.1 ± 22.8 m) and minimum
water temperatures (4.9 ± 0.1°C) during the sun culmination (sun at its
highest point in the sky) of each day. The daytime water temperature
varied between 4.7 and 5.2°C, staying at an almost constant 5°C. The
eel started to dive to deeper water around nautical twilight (sun
altitude: -11.6 ± 4.6°) and rise shallower around sunset (sun altitude:
-0.8 ± 1.4°); sun altitude and swimming depth were correlated during
the dives at dawn and ascents up at dusk. These results suggest that
the regular diel vertical migrations of Japanese eels are strictly
regulated by both light intensity and the lower limit of water
temperature. Key words: Japanese eel,
Spawning area, Diel vertical migration, Light intensity, Pop-up tag. *Correspondence: Tel & Fax: +81-742-43-9236.
E-mail: swpc@nara.kindai.ac.jp |