The structure of fish follower-feeding associations at three oceanic islands in southwestern Atlantic

Abstract

Structurally complex and competitive environments such as reef habitats may promote alternative behavioural feeding tactics in fishes. An understudied behavioural tactic is the follower-feeding association, in which individuals of a species follow (called “follower”) and benefit from the foraging activities of individuals of another species that disturbs the substrate (called “nuclear”). Here, we investigated the incidence of this tactic at three oceanic islands in the southwestern Atlantic by characterizing pairwise, and the emergent network of follower-feeding associations. We quantified associations among species according to their trophic categories, activity period, and group size. The incidence of follower-feeding associations was higher at islands with higher species richness, but the proportion of associations per species was higher at islands with lower species richness. Overall, mobile invertebrate-feeders, omnivores and macrocarnivores were the most common trophic categories engaged in this tactic. Most of follower-feeding associations involved diurnal species, which indicates that followers rely on visual cues to engage in this tactic. We also found that nuclear species were mainly solitary, while followers tended to aggregate in small- to medium-sized groups. Our study indicates that follower-feeding association is an opportunistic yet frequent feeding tactic at oceanic islands, which may stem from resource partitioning in such remote habitats.