The social behaviour of a number of fish species living in groups is characterised by the development of a dominance hierarchy. The development of dominance hierarchies involves aggressive behaviour and may be related to stress. Aggressive displays may be non-damaging or harmful to other fish. Dominance hierarchies influence choice of position in the stream and feeding opportunities in the wild and in cultured environments. Dominance may lead to greater access to resources and increased growth.
Aggression consists of threat displays and overt aggressive acts.
Fin display - Aggressors have raised dorsal fins as a threat display. Charge - A direct but slow approach towards another individual. The charging fish usually have extended fins. Chase - succession of at least two attacks towards the same fleeing individual. A bite at a closely located individual.