SOCIAL-ISOLATION, AGGRESSION, AND DOMINANCE IN ATTACKS IN JUVENILE ANGELFISH, PTEROPHYLLUM-SCALARE

The effects of social isolation on aggressive behavior and rank order have been investigated in small groups of juvenile angelfish, Pterophy llum scalare. An experimental protocol including a ''double transfer'' of the subjects was used, in which fish were transferred to new aquar ia in groups, before subsequent isolation and regrouping. A significan t decrease in aggression was observed in the first recording session f ollowing both isolation and group transfer, after which the level retu rned to that recorded in the home tanks. The social hierarchy was also perturbed, but changes generally involved the two highest ranking fis h in two out of the three groups, and were found not to be statistical ly significant. The behavior patterns are interpreted as adaptive resp onses to environmental change.