Effects of high-intensity sonar on fish

Abstract

Studies investigated the effects of exposure to low-frequency active (LFA) sonar on rainbow trout, channel catfish, and pumpkinseed sunfish using an element of the SURTASS LFA. Animals were exposed to sounds that had a received peak level of 193 dB re: 1 uPa (rms) (188.5 dB re: 1 uPa2 s SEL). Measurements were made of hearing sensitivity using auditory brainstem response and of behavioral responses. Additional studies were done on pathology of the ear and other organ systems. Trout and catfish both showed temporary threshold shifts immediately after sound exposure, while sunfish showed no threshold shift. However, the amount of threshold shift and frequencies concerned varied. In addition, trout and catfish showed immediate behavioral responses to the sound onsets and in relative distribution during sound presentation. Details of the responses differed between species. There was no mortality in any species attributable to sound exposure during or after experiments. SEM examination of hair cell ciliary bundles of the inner ears did not show any damage. Similarly, there were no effects on the swim bladder or nonauditory tissues. Overall, the effects of LFA on fish depend upon species and appear to be temporary and relatively modest. [Work supported by Chief of Naval Operations.]