Predation risk assessment by larval reef fishes during settlement-site selection

Abstract

Predation rates of marine species are often highest during the transition from the pelagic to the benthic life stage. Consequently, the ability to assess predation risk when selecting a settlement site can be critical to survival. In this study, pairwise choice trials were used to determine whether larvae of three species of anemonefish (Amphiprion melanopus, A. percula and Premnas biaculeatus) are able to (1) assess the predation risk of potential anemone settlement sites through olfactory cues alone and (2) alter their settlement choices depending on the options available (host or non-host anemone). When predation risk was assessed with host and non-host anemone species independently, all species of anemonefish significantly chose the odor associated with the low-risk settlement option over the high-risk site. Most importantly, all species of anemonefish selected water with olfactory cues from their host anemone regardless of predation risk when paired against non-host anemone odor. These results demonstrate that larval reef fishes can use olfactory cues for complex risk assessment during settlement-site selection; however, locating the correct habitat is the most important factor when selecting a settlement site.