Social behaviour, foraging efficiency and habitat utilization in a group of tropical herbivorous fish

Abstract

In this study schooling and solitary behaviour in a group of tropical herbivorous fish were compared. Three species of acanthurids are common herbivores on the coral reef off the coast of Belize, Central America. In the high spur and groove habitat, individuals of all three species of fish were seen exhibiting both solitary and schooling behaviour. Individuals commonly moved in and out of schools. Solitary fish foraged primarily in the groove microhabitat and received attacks more frequently from territorial herbivorous competitors (pomacentrids). The schooling fish foraged more frequently in the spur microhabitat and in pomacentrid territories, but received fewer attacks from territorial pomacentrids. Paired-choice feeding trials indicated that the algal turfs from the spur microhabitat were greatly preferred. Solitary individuals also visited cleaning stations more frequently. At cleaning stations, juvenile labrids removed trematodes from the acanthurid's skin. The mixed-species schooling appears to be a means by which acanthurids can forage in a microhabitat on a preferred resource while circum venting the territoriality of a herbivorous competitor. The solitary behaviour allows individuals to visit cleaning stations more frequently.