MEPS 186:265-269 (1999)  -  doi:10.3354/meps186265

Swimming depth of migrating silver eels Anguilla japonica released at seamounts of the West Mariana Ridge, their estimated spawning sites

Jun Aoyama1,*, Karen Hissmann2, Tatsuki Yoshinaga3, Seiji Sasai3, Tomoko Uto3, Hiroshi Ueda4

1Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo 164-8639, Japan
2Max-Plank-Institute of Animal Behaviour and Physiology, 82319 Seewiesen, Germany
3Irago Institute, Atsumi-cho, Atsumi-gun, Aichi 441-36, Japan
4Toya Lake Station for Environmental Biology, Faculty of Fisheries, Hokkaido University, 122 Tsukiura, Abuta-cho, Abuta-gun, Hokkaido 049-5723, Japan

ABSTRACT: Five hormone-treated female Japanese silver eels Anguilla japonica were tagged with ultrasonic transmitters and released by submersible in the West Pacific at seamounts of the West Mariana Ridge, their supposed spawning grounds. Four eels were tracked for 60 to 423 min in the vicinity of the seamounts. They did not settle at the seamounts but swam at a mean speed of 0.37 m s-1 into open water above deep ground. Their mean swimming depth ranged from 81 to 172 m. Experiments suggest that pre-matured A. japonica migrate to their spawning grounds in temperate warm water and at shallow depths.


KEY WORDS: Freshwater eel · Spawning migration · Biotelemetry · Seamounts · Swimming depth · Anguilla japonica


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