Influence of prior residents on settlement preferences in the anemonefish, Premnas biaculeatus

Abstract

Settlement preferences play a critical role in the successful transition from pelagic larvae to benthic juveniles for many coral reef organisms. Reef fish larvae are capable of recognizing and behaviorally responding to a variety of sensory cues when assessing settlement site locations. The presence of resident conspecifics for site attached coral reef fishes could indicate a quality location, but may result in negative interactions through aggression from already-established individuals. For anemonefishes, where space on a sea anemone is limited and breeding is restricted to one adult pair, settlement preferences may depend on the number and sex of the occupants. Here we undertook both aquarium-based olfactory trials and a field experiment to determine the role resident anemonefish individuals have on sea anemone site selection in the spine cheek anemonefish, Premnas biaculeatus. We show larvae are able to identify the occupant saturation state and sex of the resident occupants based on chemical cues alone, with larvae preferring the chemical cues produced by a single male to a single female, the single fish to an empty sea anemone, and an empty sea anemone to a sea anemone containing an adult pair. These behavioral preferences were reflected in the settlement preferences of larvae when assessed in the natural environment. We hypothesize that the ability of resident fish to evict incoming larvae combined with the selective pressure on larvae to locate an ideal habitat has resulted in the larval ability to accurately identify habitat where settlement and future breeding opportunities are most likely achieved.