Impacts of River-Based Air Gun Seismic Activity on Northern Fishes

Abstract

Air guns are an energy source commonly used by the oil and gas industry for seismic exploration, particularly in marine environments. Exposure to air gun noise has been shown to negatively impact marine fishes (e.g., McCauley et al. 2003); however, little is known about the potential impacts on fishes in freshwater systems. A proposal to use air guns for a seismic survey along the Mackenzie and Liard Rivers (∼1,200 km) in the Northwest Territories (NWT) led to considerable public and regulatory concern. As a result, the Canadian Department of Fisheries and Oceans (DFO) required the proponent to validate their prediction that the project will have no impacts on fish. The proponent conducted a study that showed no acute mortality associated with air gun use, although some stunning was observed in caged fish closest (2 m) to the air gun blasts (Cott et al. 2003). Outstanding data gaps associated with sublethal impacts of air gun noise (e.g., physical damage, stress, herding, and hearing loss) prompted the DFO to initiate a study, in collaboration with academic partners, to assess these impacts on northern fish in a riverine setting. The project was split into two components: 1) physiological impacts on fish hearing and ear damage and 2) behavioral impacts on free-swimming fishes.