A brief note on the relationship between residual feed intake and aggression behaviour in juveniles of African catfish Clarias gariepinus

Individual differences in maintenance levels have been related with energetically expensive processes such as aggression. This relationship is not fully understood as on one hand individuals with higher maintenance requirements seem to be more aggressive but on the other hand have smaller metabolic scopes and therefore less scope for activity. In this study the relationship between individual differences in maintenance requirements and aggression of African catfish is investigated using the residual feed intake as an approximation of maintenance requirements. Residual feed intake, defined as the difference between actual feed intake and that predicted from mean observed requirements for growth and maintenance was determined in individually housed African catfish. Afterwards, the aggressive behaviour of each individual was tested using pairwise contests. The results suggest that individuals with lower RFI (i.e. more efficient) are more aggressive. The most metabolically efficient individuals may have advantage during short and intense aggressive encounter, such as the one used in this study. Being more efficient in terms of nutrient use may therefore allow a faster but shorter term metabolic response in order to fulfil the energetic demands imposed by aggression