AimKnowledge of boldness, the propensity to take a risky decision and aggressivebehaviour is essential to culture, control or conserve any group living species. We haveanalysed the relation between boldness and aggression and the reduction of group sizeon the agonistic interaction in a freshwater shoaling fish, the climbing perch (Anabastestudineus)
MethodsThe boldness of climbing perch was tested using ‘swim-way apparatus’, consisting ofan aquarium divided to two unequal chambers using an opaque guillotine door. Thefish was introduced into the small chamber with opaque side chambers and the timetaken to initiate the exploration of the brightly lit large chamber, time spent in activelysearching it, and the frequency of switching between these habitats were recorded afterraising the door. Later these subject fish were divided in to colonies of four individualsin separate aquaria and the aggressive display (nipping) were recorded after the periodof acclimation. Variation in the aggressive display was recorded after reducing the shoalsize from four individuals to three and later to two by removing the most aggressive fishfrom the shoal.
ResultsIn this species boldness (the time taken to initiate the exploration) was found to becorrelated with the exploratory behaviour and the frequency of switching betweenthe bright and shady habitats. Differing from many other species, in climbing perchthe aggression did not show any correlation with boldness. Moreover, the level ofaggression was found to be reducing significantly when the shoal size was increasedfrom three individual to four individuals and climbing perch exhibited very high level ofaggression when they were kept in pairs.
ConservationThe result of the present study reveals that the bold individual of climbing perch arealso active explorers and can initiate the migration to new environments and canestablish new colonies there. However the lack of correlation between aggression andboldness requires further analysis since most of the species exhibited tight correlationbetween these traits. However, the enhancement of aggression with the reduction inshoal size could be dangerous for this species in the current context of habitat reductionand over exploitation of populations.