Aggressive behaviour in tiger barbs (Barbus tetrazona)

Abstract

The aim of this project was to study aggressive behaviour in tiger barbs, Barbus tetrazona, and their hierarchy systems and to determine some of the factors which influence them. The linearity of hierarchies was investigated and it was found that tiger barbs do not form stable linear hierarchies. Nor did the relative weights of fish influence their dominance/subordination relationships. The effect of the amount of cover on the outcomes of agonistic interactions was examined. A greater amount of cover resulted in earlier terminations of fights due to the loser being more able to hide from its assailant. The subordinate fish were found to play as important a role in agonistic encounters as the dominant fish. The effects of group-living on subsequent agonistic interactions was investigated to determine whether prior experience of fish from the same group had any effect on subsequent encounters. This was found not to be the case. The possibility of individual recognition taking place was also examined but was found not to be involved in the outcomes of agonistic encounters. The possibility that each fish had its own individual level of aggression was investigated. This did not appear to be the case, but rather, each individual's level of aggression was affected by the relative fighting abilities of other individuals present. However, the most subordinate fish in a group may have been adopting a different strategy, deterring them from engaging in conflicts. This strategy was possibly maintained by the presence of more dominant fish. The results obtained lead to the suggestion that the fighting ability of tiger barbs may develop through experience of fighting and differ in rate of development between individual fish.