Surveillance of Marine Mammals in the Safety Zone around an Air Gun Array with the Help of a 360° Infrared Camera System

摘要

Most countries require monitoring of marine mammals near seismic surveys in order to estimate potential impacts and/or to trigger appropriate mitigations measures. Typically, monitoring involves the use of visual observations by trained personnel, which are generally limited by periods of daylight with good visibility (e.g. not foggy etc.); even in perfect weather, marine mammal presence may be missed by the human observers. The ability to detect marine mammals missed by observers, as well as the ability to extend the observation period of marine mammals into the nightime and into other poor visibility conditions, would increase the activity time for industry and the accuracy of monitoring/mitigation compliance efforts. One technology for improving the effectiveness of monitoring is the use of infrared (IR) imaging devices. IR technology measures the heat radiated from an object, and the heat contrast between two juxtaposed objects. IR technology is well suited to marine mammal monitoring, since all marine mammals must come to the surface to breathe, and IR imaging often gives a clear temperature contrast between the animal and the water, making for easy detection through both visual and automated observations. An advanced IR camera system capable of simultaneously monitoring 360° around a vessel was tested during a two month seismic operation in the Alaskan Chukchi Sea in 2010. This particular installation allowed monitoring of 280° ahead and to the sides of the vessel with a picture refresh rate of 5 hertz (Hz). The IR pictures were displayed in real-time on two monitors, and video was recorded during marine mammal sightings for retrospective analyses. Approximately 180 whale blows were detected in the recorded IR imagery. Smaller whales (Dall’s porpoise) were detectable at distances of several hundred meters, while blows from large baleen whales were seen at distances of up to 8 kilometers (km). The IR camera was also able to detect walrus that surfaced within 1 km of the vessel, with some detection out to a maximum distance of 1.5 km. Sea state and visibility hampered the detectability for marine mammals similarly to human visual observations, but the IR camera offers excellent observations possibilities at nightime. In the tested configuration, the IR camera system showed substantial promise for improving the effectiveness of detecting marine mammals at the surface during daylight hours, and even more detection capabilities at night. In additiona, the IR camera also allows precise measurement of the distance of the marine mammal to the seismic vessel.