A behavioural reconnaissance of some Jamaican reef fishes

Three major social systems were observed: territorial, isolate, and gregarious. Territorials defend a particular area against intruders. Isolates neither chase conspecifics nor join other individuals, while gregarious species are found in groups. Some species of territorial pomacentrids were found in uni-specific colonies. As gregarious groups neared these colonies, they were attacked by several territorials. The number of chases directed against the various species of intruders was in proportion to the intruder's abundance in the study areas. Predators were uncommon and generally ignored. Isolates were either predators, or slow moving species. Gregarious species could be found in uni-specific or mixed-species groups. In mixed-species groups, there were three subunits: core, associate, and opportunist. Core species were always in the majority and led the group. Associates followed the core species for long periods of time and the opportunists were brief visitors. Quantitative comparisons between uni-specific and mixed-species groups revealed that associates tend to select the larger of the available core groups. Juveniles were also considered and compared to their adults. Juveniles did exhibit the general types of social behaviour found in adults. However, within a species, the adult's behaviour may be very different from their own juveniles. The coral, and the chases by pomacentrids, were related to the formation and dispersion of gregarious groups.