Feeding and territorial behaviour in juveniles of three co-existing triggerfishes

Of three coexisting triggerfishes, in the intertidal and immediate subtidal zones of a coral reef within the Kenting National Park, southern Taiwan, Balistoides viridescens was in the subtidal zone and foraged preferentially by nipping directly at small invertebrates among algal covered substrata. They fed also, although at a lower frequency, by using a water-jet technique to uncover prey on sandy substrata. Territory size ranged from 61.05 to 161.57 m(2) but was not related, to rates of feeding or defence. Feeding frequency was, however, positively related to the area of algae present in the territory, and inversely related to the frequency of defence. In contrast to B. viridescens, Rhinecanthus verrucosus and R. aculeatus foraged mainly in the intertidal zone when the tide was high. They fed preferentially off rocky substrata and used only nipping (not water-jetting) to secure prey. (C) 2001 The Fisheries Society or the British Isles.