Effects of riverine seismic air-gun exposure on fish hearing

Abstract

Seismic airguns produce considerable amounts of acoustic energy that have the potential to affect marine life. This study investigated the effects of exposure to an airgun array in the Mackenzie River Delta on the hearing of three fish species: northern pike (Esox lucius), broad whitefish (Coregonus nasus), and lake chub (Couesius plumbeus). Fish were placed in cages in 1.9 m of water and exposed to 5 or 20 airgun shots, while controls were placed in the same cage but without airgun exposure. Hearing in both exposed and control fish were then tested using auditory evoked potentials (AEPs). Threshold shifts were found for exposed fish as compared to controls in the northern pike and lake chub, with recovery within 24 h of exposure, while there was no threshold shift in the broad whitefish. It is concluded that these three species are not likely to be substantially impacted by exposure to a 2D airgun array used in a river seismic survey. Care must be taken in extrapolation to other species in other environments and to fishes exposed to airguns in 3D tests or where the animals are exposed to a larger number of airgun shots over a longer period of time.