Behavioral plasticity in larval reef fish: orientation is influenced by recent acoustic experiences

Animals use many different cues to orient in their environment, solve directional movement challenges, and select suitable habitat. Recent work has highlighted the importance of the ambient soundscape in providing orientation cues for larvae of coral reef fishes at the key life-history phase when they recruit from open ocean to coral reef environments. In this study, we combined acoustic conditioning with binary choice chambers and used 442 settlement-stage larvae from 4 Pomacentridae (damselfish) species (Pomacentrus amboinensis, P. brachialis, P. moluccensis, and P. nagasakiensis) to test whether responses to acoustic cues are fixed or whether behavior is influenced by recent acoustic experience. Over 8 trials, groups of wild-caught larvae that experienced noise (natural reef noise or artificial tone noise) during a 12-h conditioning period showed a positive directional response to reef noise in the chambers. Groups conditioned with reef noise responded adversely to the tone noise, whereas groups conditioned to the artificial tones were subsequently attracted by them. This plasticity in behavior suggests that settlement-stage larval reef fish (similar to 20 days old) are influenced by, and can retain information from, recent acoustic experiences. Behavioral plasticity may enable greater control by larvae over their selection of settlement sites but could also mean that anthropogenic sounds have more than masking effects on the orientation behavior of fishes.