Using fine-scale spatial analysis to study behavioural strategies prevalence in wild groups of drift-feeding fish

Abstract

Key aspects of the social behaviour of groups of drift-feeding fish can be inferred by the way space is shared between group members, because they inhabit a very dynamic and complex environment where spatial positions have a direct impact on fitness-related traits. Therefore, the spatial analysis of such a system can reveal important insights into behavioural ecology of fish, but so far, technical constraints limited this approach to only large salmonids. We used a digital imaging technique to monitor movements and behaviour of free-ranging groups of juvenile galaxiids (Galaxias anomalus) facing two contrasting physical and social contexts. We described the spatial structure of these groups and studied individual space use in relation to their social behaviour. We found that prevalence of territorial behaviour differs greatly between sites, which suggests that groups were displaying different social organisation. This study showed that detailed spatial analysis of space use and behaviour of drift-feeding fish could provide new insights into the social organisation of group-living animals.