Journal Article

Direct measurement of the swimming speed, tailbeat, and body angle of Japanese flounder (<i>Paralichthys olivaceus</i>)

Ryo Kawabe, Yasuhiko Naito, Katsufumi Sato, Kazushi Miyashita and Nariharu Yamashita

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 61, issue 7, pages 1080-1087
Published in print January 2004 | ISSN: 1054-3139
Published online January 2004 | e-ISSN: 1095-9289 | DOI:
Direct measurement of the swimming speed, tailbeat, and body angle of Japanese flounder (Paralichthys olivaceus)

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  • Environmental Science
  • Marine and Estuarine Biology


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It is well known that flatfish species such as plaice can utilize the selective tidal stream to conduct vertical movements. However, detailed description of actual swimming behaviour is lacking, principally as a result of the difficulties encountered in monitoring the behaviour of flatfish in the open sea. The present study describes the use of a newly developed data-logger in obtaining simultaneous recordings of the swimming speed, depth, tailbeat, and body angle of free-ranging Japanese flounder (Paralichthys olivaceus) in the open sea. Our data indicate that Japanese flounders adopt a tailbeat-and-glide behaviour. They are found to glide downward without tailbeats for propulsion, and only during the ascent phase are tailbeats conducted. Flounders move horizontally at speeds of 0.59–1.23 km d−1 and at a maximum speed of 0.70–0.82 km h−1 in the open sea. Modal flounder swimming speeds are 30–40 cm s−1 (0.57–0.76 and 0.58–0.77 BL s−1), i.e. sometimes lower than the threshold of the speed sensor. In most cases, however, tailbeat oscillations occur at frequencies of 1.2–1.4 Hz. Moreover, flounders travel at a significantly steeper angle during the ascent phase than during the descent phase. In both cases it is believed that flounder optimize the energetic costs of migration, as has been shown for tuna, sharks, and seals.

Keywords: acceleration; beat-and-glide behaviour; body angle; Japanese flounder; swimming speed; tailbeat frequency; vertical movement

Journal Article.  4521 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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