Evaluating effects of dredging-induced underwater sound on aquatic species : a literature review

At any given moment, there may be multiple underwater sounds emanating from both natural and anthropogenic sources.Dredging activities such as the excavation, transit, and placement of material generate underwater sound.This report documents research into the biological effects of underwater sound from dredging and other anthropogenic sources to help evaluate the potential ecological risks of dredging activities.Effects data generated from exposures to anthropogenic sound sources indicate that dredging-induced sounds do not pose a significant risk of direct injury or mortality to aquatic biota.A notable exception, and much less common, is blasting activities used to remove rock and other hard substrata in navigation channels.In terms of potential non-lethal responses, low-frequency sounds produced by dredging overlap with the hearing frequency ranges of select fish and mammal species, which may pose risks for auditory temporary threshold shifts, auditory masking, and behavioral responses.To better understand the ecological risk associated with dredging sounds, a risk-based approach is needed that utilizes the available data and other site-specific information appropriate for evaluating underwater sound.The information reported herein can be used in an exposure assessment as part of a broader framework for evaluating and managing underwater sound effects on aquatic life.