Sound communication by the forceps fish, Forcipiger flavissimus (Chaetodontidae)

Abstract

The forceps fish, Forcipiger flavissimus (family Chaetodontidae), lacks the anterior swim bladder horns and laterophysic connection that are proposed to improve processing of acoustic signals in the genus Chaetodon. Despite the lack of hearing specializations, laboratory experiments using hydrophones synchronized to video revealed the forceps fish produce at least three sounds: (1) a pulse (21‐ms duration, peak frequency=318 Hz) associated with rapid cranial elevation, (2) a low‐frequency pulse (9‐ms duration, peak frequency=41 Hz) associated with anal fin retraction and elevation, and (3) a high‐frequency broadband click (3‐ms duration, peak frequency=7924 Hz) associated with tail slap behavior. Auditory evoked potential experiments demonstrate that hearing thresholds for this species are 10–21 dB higher than Chaetodon in the 200–600‐Hz band. High‐speed kinematic analyses show that motor movements associated with some acoustic behaviors are different than those in Chaetodon, thus the presence of sound production may be the ancestral state for the family but the mechanisms are divergent. Field observations on Hawaiian reefs reveal that forceps fish occur in pairs and trios that may be haremic, and use acoustic communication among group members.[Work supported by NSF IBN0137883 to TT.]