Effects of social organization on the feeding of the striped parrotfish, Scarus iseri

Abstract

Parrotfishes contribute to important reef processes through their feeding. Individuals may join groups with distinctive social behavior, with unknown implications for their feeding ecology and, ultimately, their functional roles in reef systems. Using Scarus iseri populations in Isla Colon, Panama, we investigated whether individuals belonging to the two main social groups formed by this species (‘Territorial’ and ‘Stationary’ groups) differed in their feeding preferences. Territorial groups had access to a diversity of potential food sources, yet showed selectivity for feeding on sandy substrate. Stationary groups showed high selectivity for filamentous algae, despite this resource being less available for this group than for territorial individuals. Initial phase fish had higher bite rates on plants than terminal phase individuals, while the latter had higher bite rates on soft substrata and sponges, both indicating detritus consumption. Parrotfish sociobiology may therefore influence their relative ecosystem impact, with territorial and terminal individuals in both social groups more involved in the detrital food web and stationary groups contributing to a greater extent on algal removal.