ABSTRACT
All anemonefish species can produce two types of sounds. The first class concerns agonistic sounds that are produced during territory defence and probably to establish social hierarchy between individuals. The second class relates to submissive sounds that are emitted in reaction to aggressive acts by dominant individuals. In both types of sounds, irrespective of the sexual status, frequency is highly related to fish size: smaller individuals produce pulses of higher frequency and shorter duration than larger individuals. Consequently, these sonic features within a group may convey information on the social rank of the emitter within the group. This relationship between fish size and both dominant frequency and pulse duration could concern all the Amphiprionini tribe. It highlights the use of a highly conservative vocalization mechanism. Aggressive sounds are initiated by buccal jaw teeth snapping caused by rapid mouth closure attributed to a sonic ligament. We hypothesize that the slam provokes bone vibrations. As the close association of the rib cage and the swimbladder wall would be analogous to a membrane loudspeaker, vibrations would cause shaking of this membrane and cause the second part of the sound. The sound-producing mechanism related to submissive sounds is still not known.
