Hydroacoustic measurements of the behavioral response of arctic riverine fishes to seismic airguns.

Seismic surveys for hydrocarbon exploration in the Mackenzie River involve the use of airguns. Airguns produce a repetitive, intense, low-frequency sound that has the potential to cause physiological damage and behavioral changes in fishes. Some of these impacts have been documented in marine environments but few studies have been conducted in freshwater systems where the confining nature of the environment produces a different acoustic regime and could constrain possible fish response. In the current study, hydroacoustic surveys are conducted in the presence of airgun firing in the Mackenzie River to determine if fish behavior can mitigate or enhance the potential impact of this sound. It is shown that fish behavioral characteristics measured in this study are generally not changed by the presence of airgun noise. The most likely mechanism to facilitate a severe physiological effect in fishes from a mobile airgun firing is a herding response in front of the airgun, resulting in prolonged exposure to the noise. Analysis of tracked fish directional movement does not indicate that herding behavior occurs. Consequently, no evidence is found to indicate that fishes in this study would sustain severe physiological damage from this airgun seismic survey.