Towards an isolation syndrome for the angelfish, Pterophyllum scalare

The behaviour of individual angelfish, Pterophyllum scalare , isolated for 4 days in the laboratory has been compared with that of the same fish in groups. Locomotor activity, feeding behaviour, aggression and responses to novel stimuli have been studied. Isolated fish are less active, approach the surface to feed less readily and are slower to recover from sudden mechanical shock than when kept in a group. In contrast, isolates are more attentive to a gradually‐applied, novel, visual stimulus. The aggressive behaviour of post‐isolates on return to the group tank was not significantly different from that shown before isolation.