Composition and behavior of mixed-species foraging groups of reef fish in the Lakshadweep islands, India

Abstract

Mixed-species foraging groups of reef fishes, although relatively common in occurrence, have historically received little attention. Most studies on this topic have been descriptive accounts of specific associations. In this study, we collected data on mixed-species foraging groups seen in the Lakshadweep islands, resulting in a dataset of 1289 groups. Data was collected from both reefs and lagoons of three islands (Kadmat, Kavaratti, and Agatti) within the Lakshadweep Archipelago over a period of three years. Cluster analysis revealed nine categories based on species composition in groups: parrotfish, juveniles, surgeonfish (small), surgeonfish (large), Anampses spp., wrasses, Parupeneus macronema, Parupeneus barberinus, and other goatfish groups. The clusters are named based on the nuclear species or most frequently seen species within the groups. These groups are distinct not only in terms of composition but also other parameters such as behavior (shoaling or attendant groups), habitat affinity, and group cohesion. Groups comprising herbivorous species such as parrotfish and surgeonfish were almost entirely shoaling in nature (large groups without nuclear individuals), whereas goatfish and wrasses tended to form smaller attendant associations. Groups also occupied different habitat types; for example, parrotfish and P. barberinus groups were seen mostly in lagoons while surgeonfish, wrasses, and P. macronema groups were more abundant on reefs. Our findings suggest that mixed-species foraging groups in fishes are comprised of distinct compositional categories that vary in behavior, cohesion, and habitat affinity.