Spotlined sardine Sardinops melanostictus listensto 1-kHz sound by using its gas bladder

ABSTRACT:   The auditory characteristics of pelagic fish have received lessattention compared to those of benthic or freshwater fish species,even though underwater sounds are considered to affect their behavior.Audiograms of five spotlined sardines were obtained using the auditorybrainstem response technique in which the evoked potential on theskin covering the head of the fish was measured. The auditory brainstemresponse is a non-invasive electrophysiological method that enablesthe auditory threshold level of fragile species, such as spotlinedsardines, to be measured. The gas bladder of the spotlined sardinehas been considered as possibly contributing to an enhancement intheir hearing. In the test, the sound absorption profile of sardineswas also measured. The frequency at the lowest auditory thresholdlevel (i.e. the most sensitive frequency) and absorption were foundat 1024 Hz and 1040 Hz, respectively. The spotlinedsardine was found to be sensitive to sounds at relatively higherfrequency ranges compared to other seawater fishes and the gas bladderis seen to play a significant role in detecting sound.