Ontogenetic shifts in the habitat associations of butterflyfishes (F. Chaetodontidae)

Abstract

The habitat associations of species are vital in determining an organism’s vulnerability to environmental and anthropogenic stress. In the marine environment, post-settlement processes such as ontogenetic shifts in habitat use can affect this vulnerability by subjecting a species to differing biological and environmental conditions at various life stages. This study documents the habitat associations of adult and juvenile butterflyfishes on an inshore reef of the Great Barrier Reef (GBR) to investigate if ontogenetic shifts in habitat use occur, and if such shifts relate to the trophic ecologies of species. Coral-feeding species displayed highly concordant distributions among adults and juveniles. In contrast, adults and juveniles of species with wider dietary selectivities (generalists) displayed significantly different distributions across reef zones. Juvenile generalist feeders were limited to the shallow, patchy areas of the reef flat whilst adult conspecifics displayed comparatively wide distributions. Butterflyfishes with a heavy reliance on corals for food appear to settle preferentially in areas with high abundances of adult conspecifics, which may partially explain why coral specialists are more vulnerable to localized depletion events. In contrast, generalist species utilize distinct habitats as adults and juveniles, suggesting that generalist butterflyfishes expand their ranges and are therefore subjected to changing environmental conditions as they reach adulthood.