title: Light-sensitive vertical migration of the Japanese eel Anguilla japonica revealed by real-time tracking and its utilization for geolocation.
abstract: Short-time tracking (one to eight days) of the Japanese eel (Anguilla japonica) using ultrasonic transmitter was performed in the tropical-subtropical area adjacent to the spawning area and temperate area off the Japanese Archipelago. Of 16 eels (11 wild and five farmed) used, 10 wild eels displayed clear diel vertical migration (DVM) from the beginning, while the other five farmed eels tracked for 19 to 66 hours did not. During daytime, a significantly positive correlation between migration depth and light intensity recorded on the vessel was observed in the 10 wild eels, indicating that the eels were sensitive to sunlight even at the middle to lower mesopelagic zone (500 to 800 m). During nighttime, the eel migration depth was observed to be associated with the phase, rising and setting of the moon, indicating that the eels were sensitive to moonlight at the upper mesopelagic zone (<300 m). Two of 10 wild eels were in the yellow stage but shared similar DVM with the silver stage eels. Swimbladders of three silver stage eels were punctured before releasing, but very little effect on DVM was observed. The eels very punctually initiated descent upon nautical dawn and ascent upon sunset, enabling us to determine local times for sunrise and sunset, and hence this behavior may be used for geolocating eels. In fact, estimated positions of eels based on the depth trajectory data were comparable or even better than those obtained by light-based archival tag in other fish species.
authors: National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan.
authors: Seinen
authors: S
authors: Chow
authors: National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan.
authors: Makoto
authors: M
authors: Okazaki
authors: National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan.
authors: Tomowo
authors: T
authors: Watanabe
authors: National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan.
authors: Kyohei
authors: K
authors: Segawa
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Toshihiro
authors: T
authors: Yamamoto
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Hiroaki
authors: H
authors: Kurogi
authors: National Research Institute of Aquaculture, Nakatsuhamaura, Mie, Japan.
authors: Hideki
authors: H
authors: Tanaka
authors: Chiba Prefectural Fisheries Research Center Freshwater Station, Sakura, Chiba, Japan.
authors: Ken-Ichiro
authors: K
authors: Ai
authors: Chiba Prefectural Fisheries Research Center Freshwater Station, Sakura, Chiba, Japan.
authors: Miho
authors: M
authors: Kawai
authors: Kagoshima Prefectural Fisheries Technology and Development Center, Ibusuki, Kagoshima, Japan.
authors: Shin-Ichi
authors: S
authors: Yamamoto
authors: Kyushu University, Fukuoka, Japan.
authors: Noritaka
authors: N
authors: Mochioka
authors: Nihon University, Fujisawa, Kanagawa, Japan.
authors: Ryotaro
authors: R
authors: Manabe
authors: The University of Tokyo, Kashiwa, Chiba, Japan.
authors: Yoichi
authors: Y
authors: Miyake
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D004524:Eels / Q000502:physiology*; D008027:Light