Mass schooling and mortality of Canthigaster bennetti in Sulawesi

Abstract

[Extract] Published accounts of puffer fishes of the genus Canthigaster describe these species as territorial and occurring at low densities (Sikkel 1990 and references within). Here, we provide the first account of mass schooling in any Canthigaser species: C. bennetti around the Togean Islands, Sulawesi, in December 2009. Schools of >10,000 C. bennetti (Fig. 1a) were observed around the fringing reefs of the volcanic island Una Una (0°11'30"S, 121°39'30"E). These single-species schools were observed at depths of 7–30 m, and all individuals comprising them were ~4 cm long. School members displayed relatively coordinated group behaviour, i.e., facing and moving in the same direction. Schools were often several metres away from the reef, strongly contrasting the close substrate association of C. bennetti on the Great Barrier Reef, Australia (pers. obs.).