Cetacean behavioral responses to noise exposure generated by seismic surveys: how to mitigate better?

Clara Monaco Clara Monaco,L Mario Tringali L Mario Tringali,Francisco Carrión Francisco Carrión,Jesús M Ibáñez Jesús M Ibáñez

doi:10.4401/ag-7089

Abstract

<p>Cetaceans use sound in many contexts, such as in social interactions, as well as to forage and to react in dangerous situations. Little information exists to describe how they respond physically and behaviorally to intense and long-term noise levels. Effects on cetaceans from seismic survey activities need to be understood in order to determine detailed acoustic exposure guidelines and to apply appropriated mitigation measures. This study examines direct behavioral responses of cetaceans in the southern Mediterranean Sea during seismic surveys with large airgun arrays (volume up to 5200 ci) used in the TOMO-ETNA active seismic experiment of summer 2014. Wide Angle Seismic and Multi-Channel Seismic surveys had carried out with refraction and reflection seismic methods, producing about 25,800 air-gun shots. Visual monitoring undertaken in the 26 daylights of seismic exploration adopted the protocol of the Joint Nature Conservation Committee. Data recorded were analyzed to examine effects on cetaceans. Sighting rates, distance and orientation from the airguns were compared for different volume categories of the airgun arrays. Results show that cetaceans can be disturbed by seismic survey activities, especially during particularly events. Here we propose many integrated actions to further mitigate this exposure and implications for management.</p>

Highlights

Seismic surveys used for monitoring reserves of fossil-fuel and to study tectonics and dynamics of the seafloor crust, are anthropogenic noise sources that may interfere with natural functions of cetaceans, producing different behavioral reactions in relation to the context, the species and their sex or age [Gordon et al 2004; Hildebrand 2005]
Seismic surveys are characterized by intermittent sound pulses that are more intense than the continuous noise emitted by most industrial noises in the ocean, with peak frequency bands overlapping those used by cetacean in many contexts, such as in social interactions, as well as to forage and in dangerous situations [Finneran et al 2000; Southall et al 2007; Heide-Jørgensen et al 2013]
Existing protocols were not applied in all the oceans and not always the implemented strategies are adapted to survey areas

Summary

Introduction

Seismic surveys used for monitoring reserves of fossil-fuel and to study tectonics and dynamics of the seafloor crust, are anthropogenic noise sources that may interfere with natural functions of cetaceans, producing different behavioral reactions in relation to the context, the species and their sex or age [Gordon et al 2004; Hildebrand 2005].Marine mammals have a great ability to perceive biologically important sounds in water, but this capacity is endanger in presence of acoustic disturbance human-generated that significantly contribute to noise in the marine environment.Seismic surveys are characterized by intermittent sound pulses that are more intense than the continuous noise emitted by most industrial noises in the ocean, with peak frequency bands overlapping those used by cetacean in many contexts, such as in social interactions, as well as to forage and in dangerous situations [Finneran et al 2000; Southall et al 2007; Heide-Jørgensen et al 2013].Noise generated by seismic surveys may overlap with the low frequency sounds of baleen whales, masking long distance communication between individuals and precluding the detection of other feeble sounds [Evans and Nice 1996]. Temporal avoidance of cetaceans could be a consequence of avoidance reaction of fish during seismic surveys These factors may induce in cetaceans different stress responses and behavioral alterations [Gordon et al 2004] but little information exists to describe how they respond physically and behaviorally to intense and long-term noise levels. Effects from seismic survey activities need to be better understood in order to regulate detailed acoustic exposure guidelines and to apply mitigation measures appropriated to species and areas of investigation. For this reason, direct observation is very important to detect cetaceans and take action when necessary. Visual monitoring can ensure that the source is shut down whenever an animal is observed within or

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Results

Conclusion