Shoaling and aggressive behaviour in juvenile fighting fish (Betta splendens)

Abstract

The fighting fish (Betta splendens) is known for its aggressive behaviour. In the wild, the adult fighting fish are
territorial and show aggressive behaviour. Previous studies showed that adult fighting fish associated with
conspecifics showed shoaling behaviour in the laboratory. However, no previous studies have investigated shoaling
behaviour in juvenile fighting fish and it could have implication for commercial breeding. Therefore, we examined
shoaling preference and aggressive behaviour of the juvenile male fighting fish by using binary choice experiments
in the laboratory. When testing these two kinds of behaviour, the test fish were given a choice between a female
juvenile fish shoal and a male juvenile fish shoal in order to evaluate whether juvenile male fighting fish preferred
shoaling with the same sex or different sex before being reared individually. It was found that males showed no
significant difference either in shoaling preference or aggressive behaviour. However, the size of male test fish was
positively correlated with aggressive behaviour. Therefore, large juvenile male fighting fish should be reared
separately from shoals in the fish culture.