Ontogenetic changes in habitat selection during settlement in a coral reef fish : ecological determinants and sensory mechanisms

Abstract

The behavior of marine larvae during and after settlement can help shape the distribution and abundance of benthic juveniles and therefore the intensity of ecological interactions on reefs. Several laboratory choice-chamber experiments were conducted to explore sensory capabilities and behavioral responses to ecological stimuli to better understand habitat selection by "pre-metamorphic" (larval) and "post-metamorphic" (juvenile) stages of a coral reef fish (Thalassoma hardwicke). T. hardwicke larvae were attracted to benthic macroalgae (Turbinaria ornata and Sargassum mangarevasae), while slightly older post-metamorphosed juveniles chose to occupy live coral colonies (Pocillopora damicornis). Habitat choices of larvae were primarily based upon visual cues and were not influenced by the presence of older conspecifics. In contrast, juveniles selected live coral colonies and preferred those occupied by older conspecifics; choices made by juveniles were based upon both visual and olfactory cues from conspecifics. Overall, the laboratory experiments suggest that early life-history stages of T. hardwicke use a range of sensory modalities that vary through ontogeny, to effectively detect and possibly discriminate among different microhabitats for settlement and later occupation. Habitat selection, based upon cues provided by environmental features and/or by conspecifics, might have important consequences for subsequent competitive interactions