Marine Biodiversity Records

Research Article

Observations of schooling behaviour in the oval squid Sepioteuthis lessoniana in coastal waters of Okinawa Island

Chikatoshi Sugimotoa1, Ryoko Yanagisawaa1 p1, Ryuta Nakajimaa2 and Yuzuru Ikedaa1 c1

a1 Department of Chemistry, Biology and Marine Sciences, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan

a2 Department of Art and Design, University of Minnesota, Duluth, Minnesota 55812-3041, USA

Abstract

The schooling behaviour of the oval squid Sepioteuthis lessoniana was observed over 4 summers at 3 observation sites in the coastal waters of Okinawa Island, Ryukyu Archipelago, Japan. During this field study, 3 static appearances (belt, ball and sheet shape) and 2 transitional appearances (high and low density) were noted, recorded and described. In addition to formations, a member of S. lessoniana schools also displayed particular and repeated behavioural patterns such as vanguard and intimidating display. The 3 observation sites were tropical coral reefs near the coastline at a depth of 1 to 15 m on an average. All participating observers snorkelled and were equipped with various underwater digital video and photographic cameras. The schools observed consisted of 8 to over 100 members with a wide range of body sizes. Despite these biological and locational differences, both static and transitional appearances were consistently observed with equally consistent individual behavioural patterns. There have been studies on related species, Sepioteuthis sepioidea, at the San Blas Islands along the Caribbean coast of eastern Panama, and the same species, S. lessoniana, at a different geographical location, Casuarina Beach on Lizard Island, Australia. The findings of this study are consistent with those reported previously, with some notable differences.

(Received August 03 2012)

(Accepted January 14 2013)

Keywords

  • Cephalopoda;
  • oval squid;
  • follower;
  • leader;
  • school;
  • vanguard

Correspondence

c1 Correspondence should be addressed to: Y. Ikeda, Department of Chemistry, Biology and Marine Sciences, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan email: ikeda@sci.u-ryukyu.ac.jp

p1 Present address: Ocean Planning Corporation, Urasoe, Okinawa 901-2102, Japan