MEPS 285:213-222 (2005)  -  doi:10.3354/meps285213

ABSTRACT: Recent evidence suggests that pelagic larvae of coral reef fishes are active in their dispersal and return to a reef; however, the mechanisms used to navigate are unknown. Sound is a potentially important cue for organisms in marine environments, especially in noisy environments like coral reefs. The auditory brainstem response (ABR) technique was used to measure hearing of a wide size range of sergeant major damselfish Abudefduf saxatilis. Complete audiograms were measured for 32 fish ranging in size from 11 to 121 mm. Significant effects of standard length on hearing thresholds at 100 and 200 Hz were detected. At these lower frequencies, thresholds increased with an increase in size. All fish were most sensitive to the lower frequencies (100 to 400 Hz). The frequency range over which fish could detect sounds was dependent upon the size of the fish; the larger fish (>50 mm) were more likely to respond to higher frequencies (1000 to 1600 Hz). A. saxatilis has poor hearing sensitivity in comparison to other hearing generalists including other species of pomacentrids. In consideration of the high hearing thresholds found in this study in comparison to recorded ambient reef noise, it is unlikely that sound plays a significant role in the navigation of the pelagic larvae of sergeant majors returning to the reef from long distances (>1 km), but it may play a role in short-range orientation (<1 km).

KEY WORDS: Auditory brainstem response · ABR · Hearing sensitivity · Larval settlement