Pair-formation in coral reef fishes: An ecological perspective

Abstract

Pair-formation is a common social system among animals. However, the use of the term ‘pairformation’ is often ambiguous, and the assumed reproductive importance of pairing often supersedes consideration of aspects that are more social or ecological. This review provides a new socialecological definition of pair-formation, examines the prevalence of pair-formation among coral reef fishes, and assesses the ecological and reproductive characteristics of pair-forming reef fishes. Of 1981 Indo-Pacific reef fish species examined in this review, 341 (17.2%) are reported to live in pairs. Pair forming has been reported in 29 families, with 5 families (Malacanthidae, Chaetodontidae, Siganidae, Syngnathidae, Ptereleotridae) having more than half of their species reported to form pairs. Two traits appear to favour the formation of social, cooperative pairs: (1) foraging on small, benthic, and relatively immobile prey; and (2) living in burrows. In contrast, there are limited similarities among pair-forming species with regard to their mating system or spawning mode. It appears that the basis of pair-formation in reef fishes is complex and may involve a range of ecological factors related to food procurement and predation risk.