Effects of pile driving on fishes

Abstract

We examined the physiological effects of impact pile driving on fishes using a specially designed tube that allows replication of the far field acoustic conditions of impulsive stimuli. Studies show that the received signal levels needed to result in onset of effects is a combination of single strike sound exposure level (SELss) and cumulative sound exposure level (SELcum), although not in an equal energy relationship. In contrast to current interim regulations, which indicate that the onset of physiological effects occurs at 187 dB SELcum, our experimental results for six species of fishes showed that the onset of physiological effects, none of which produced mortality, was at about 207 dB SELcum. This onset SELcum had to be at least 7–10 dB higher to result in effects that could potentially be mortal. Additional studies showed that fishes can recover from the effects of pile driving and that a fish species without a swim bladder showed no effects, at least up to an SELcum of 216 dB. Investigations on the effects of pile driving on sensory hair cells of the inner ear, an analog for hearing loss, showed that damage only occurred at SELcum that are substantially higher than onset of other effects.